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CHAPTER 3 Muscular System Please read carefully the following "introduction" (paragraphs A-C) before coming to class, and at any rate before you begin dissecting. INTRODUCTION A. MUSCLES AND THEIR STRUCTURE Muscles are organs whose basic task is the conversion of chemical energy into mechanical energy. This energy conversion is brought about by the action of muscle tissue, which is a prime constituent of every muscle. Note that the term "muscle" is often used ambiguously, to refer either to an organ or a tissue. Please be careful in your own use to distinguish muscles, which are organs, from muscle tissue. Muscles are composed largely, but never entirely, of muscle tissue; connective tissue (of the "regular," dense variety) is also always present. Furthermore, muscle tissue often occurs in organs that are not muscles, such as the heart, stomach, uterus, or intestine. The fleshy part of a muscle is called its belly. The belly is made up largely of parallel fibers of muscle tissue, with a sheath of dense, regular connective tissue surrounding each bundle. Sometimes the muscle tissue does not extend all the way to the attached end of a muscle, and a tendon is formed, consisting of the regular, dense connective tissue only. Tendons are typically long and string-shaped, but occasionally they are broad, flat, and sheetlike; such a sheetlike tendon is known as an aponeurosis. The attached ends of muscles are important to the student in the recognition and identification of muscles during dissection. The fixed or proximal end of a muscle, or the end closer to the center of the body, is called its origin. (A muscle may have several origins; if they are distinctly separated, the muscle is described as having several heads.) The more remote, more distal, or more movable end of a muscle is known as its insertion, although 15

A Laboratory Guide to Frog Anatomy || Muscular System

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Page 1: A Laboratory Guide to Frog Anatomy || Muscular System

CHAPTER 3

Muscular System

Please read carefully t he f o l l o w i n g " i n t r o d u c t i o n " ( pa rag raphs A - C ) before c o m i n g to c lass, a n d at any rate before y o u b e g i n d i s s e c t i n g .

INTRODUCTION

A. MUSCLES AND THEIR STRUCTURE

Muscles are o r g a n s w h o s e bas ic task is t h e c o n v e r s i o n of c h e m i c a l energy in to m e c h a n i c a l energy . Th i s ene rgy c o n v e r s i o n is b r o u g h t a b o u t by t he ac t i on of muscle t issue, w h i c h is a p r i m e c o n s t i t u e n t of every m u s c l e . Note tha t t he t e r m " m u s c l e " is o f ten used a m b i g u o u s l y , t o refer e i the r t o an o r g a n or a t i ssue . Please be ca re fu l in y o u r o w n use t o d i s t i n g u i s h muscles, w h i c h are o r g a n s , f r o m muscle tissue. M u s c l e s are c o m p o s e d large ly , bu t never en t i re ly , of m u s c l e t i s sue ; c o n n e c t i v e t i ssue (of t h e " r e g u l a r , " dense var iety) is a lso a lways present . F u r t h e r m o r e , m u s c l e t i ssue o f t en o c c u r s in o r g a n s tha t are no t musc les , s u c h as t h e hear t , s t o m a c h , u te rus , or in tes t ine .

T h e f leshy par t of a m u s c l e is ca l l ed i ts belly. T h e bel ly is m a d e u p la rge ly of para l le l f i be rs of m u s c l e t i ssue , w i t h a shea th of dense , regu la r c o n n e c t i v e t i ssue s u r r o u n d i n g each b u n d l e . S o m e t i m e s t h e m u s c l e t i ssue does no t ex tend all t he way to t he a t t ached e n d of a m u s c l e , a n d a t endon is f o r m e d , c o n s i s t i n g of t he regu lar , dense c o n n e c t i v e t i ssue on ly . T e n d o n s are t yp i ca l l y l o n g a n d s t r i n g - s h a p e d , bu t o c c a s i o n a l l y t hey are b r o a d , f la t , a n d shee t l i ke ; s u c h a shee t l i ke t e n d o n is k n o w n as an aponeurosis .

The a t t ached ends of musc les are i m p o r t a n t t o t h e s t u d e n t in t he r e c o g n i t i o n a n d i den t i f i ca t i on of m u s c l e s d u r i n g d i s s e c t i o n . T h e f i xed o r p r o x i m a l e n d of a musc le , or t h e e n d c lose r t o t h e cen te r of t h e body , is ca l led its origin. (A m u s c l e may have severa l o r i g i n s ; if t hey are d i s t i nc t l y sepa ra ted , t h e m u s c l e is d e s c r i b e d as hav ing severa l heads. ) T h e m o r e r e m o t e , m o r e d is ta l , o r m o r e m o v a b l e e n d of a m u s c l e is k n o w n as its insert ion, a l t h o u g h

15

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16 A Labo ra to r y G u i d e t o F rog A n a t o m y

t he d i s t i n c t i o n be tween o r i g i n a n d i nse r t i on is occas iona l l y an a rb i t ra ry one . If o n e e n d of a m u s c l e is t e n d i n o u s o r a p o n e u r o t i c , it is usua l l y t h e i nse r t i on .

S. TERMS OF MOVEMENT

Be fo re y o u p r o c e e d any fu r the r , m a k e su re t ha t y o u u n d e r s t a n d t h e f o l l o w i n g t e r m s of m o v e m e n t , used in c o n n e c t i o n w i t h m u s c l e d e s c r i p t i o n s :

Extension, F lexion: These are t he m o s t i m p o r t a n t a n d m o s t gene ra l t e r m s . E x t e n s i o n is t he o p e n i n g of a j o i n t t o a w i d e r o r m o r e o b t u s e a n g l e ; f l e x i o n is t h e c l o s i n g of a j o i n t t o a sma l l e r o r m o r e a c u t e ang le . T h e c u r l i n g o f t h e f i nge rs , o r t he b e n d i n g of t h e e l b o w , are b o t h e x a m p l e s of f l e x i o n ; t h e s t r a i g h t e n i n g o u t of t he f i nge rs o r t h e e l b o w are e x a m p l e s o f e x t e n s i o n .

Abduct ion, Adduct ion: T h e b e n d i n g of a s t r u c t u r e t o o n e s ide of i ts neu t ra l o r cen t ra l p o s i t i o n is ca l led a b d u c t i o n ( f r om La t in ato-, in t h i s case m e a n i n g " a w a y f r o m " ) ; t he re tu rn of a s t r uc tu re t o w a r d i ts neu t ra l o r cen t ra l p o s i t i o n is ca l led a d d u c t i o n ( f r om La t in acf-, m e a n i n g " t o w a r d " ) . T h e s p r e a d i n g apar t of t he f i nge rs is an e x a m p l e of a b d u c t i o n ; t he b r i n g i n g t o g e t h e r of t h e sp read f i nge rs is ca l l ed a d d u c t i o n .

Protract ion, Retract ion: A m o v e m e n t f o r w a r d o r c ran ia l l y is ca l l ed p r o t r a c t i o n ; a m o v e m e n t cauda l l y o r a w i t h d r a w a l is ca l l ed r e t r ac t i on .

Types of ro ta t i ona l m o v e m e n t :

Homolatera l rotation is t h e dex t ra l ( c l ockw ise ) r o t a t i on of t h e head o r o the r m e d i a n s t r uc tu re by a m u s c l e o n the r i gh t s ide , or s in is t ra l ( c o u n t e r c l o c k w i s e ) r o ta t i on by a m u s c l e o n t h e left s ide . Contra la tera l rotation is t h e s in is t ra l r o ta t i on of a m e d i a n s t r u c t u r e by a m u s c l e o n t he r i gh t s ide , o r i ts dex t ra l r o ta t i on by a m u s c l e o n t h e left s ide .

Lateral rotation is t h e dex t ra l r o ta t i on of a r igh t , o r s in is t ra l r o ta t i on o f a left pa i red s t r u c t u r e . Med ia l rotation is t h e dex t ra l r o ta t i on o f a left , or s in is t ra l r o ta t i on of a r i gh t pa i red s t r u c t u r e . Supinat ion is a spec ia l t e r m fo r t he latera l r o ta t i on of t h e f o r e a r m ; pronat ion is a spec ia l t e r m fo r t h e med ia l r o ta t i on of t h e f o r e a r m .

Elevat ion, Depress ion: Eleva t ion (or levation) is a m o v e m e n t do rsa l l y o r a ra i s ing . Dep ress ion is a m o v e m e n t vent ra l l y or a l o w e r i n g .

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M u s c u l a r Sys tem 17

C. THE USE OF "LEVELS"

In t he use of any d i ssec t i on m a n u a l , t h e s t u d y of m u s c l e s is o f t en t h e m o s t a r d u o u s a n d f r us t r a t i ng of tasks f o r s t u d e n t a n d t eache r a l i ke . The re are near ly 200 musc les in t h e f r o g ( c o u n t i n g t h e b i la te ra l l y pa i red m u s c l e s o n l y once) , a n d it is usua l ly no t necessary fo r even t h e a d v a n c e d s t u d e n t s t o learn each a n d every o n e o f t h e m . Yet , even t h e b e g i n n i n g s t u d e n t o u g h t t o app rec ia te h o w n u m e r o u s t h e m u s c l e s of t h e b o d y real ly are , even t h o u g h he may be requ i r ed t o learn t he n a m e s of o n l y a f ew .

Mos t l abo ra to ry m a n u a l s s i m p l y o m i t ha l f o r m o r e of t h e m u s c l e s , a n d t h e s tuden t t h e n fa i ls t o a p p r e c i a t e tha t he is l ea rn i ng on l y a s m a l l f r a c t i o n of the i r n u m b e r . O the r m a n u a l s l ist t o o m a n y musc les , a n d t h e b e g i n n i n g s t u d e n t r i gh t fu l l y resents t h e fac t t ha t he has t o learn al l o f t hese . M o s t f r us t ra t i ng l y , t he s t uden t may acc iden ta l l y e n c o u n t e r a m u s c l e no t l is ted in h is m a n u a l , a n d w h e n he asks, " w h a t m u s c l e is í h / s ? " , he o f t en f rus t ra tes no t on ly h imsel f , bu t h is i n s t r uc to r as w e l l .

It seems tha t a l abo ra to ry m a n u a l s h o u l d l ist al l t h e m u s c l e s , o r near ly a l l , bu t tha t t h e i ns t r uc to r s h o u l d ass ign on l y a se lec t n u m b e r of t hese t o t h e s tuden t . W i t h mos t l abo ra to ry m a n u a l s , s u c h se lec t i on is very b o t h e r s o m e t o t he i ns t ruc to r , a n d is t h e r e f o r e ha rd l y ever m a d e ; t h e s t u d e n t s are e i the r o v e r b u r d e n e d w i t h t he l ea rn ing of t o o m a n y musc les , or e lse t h e s tudy of musc les is o m i t t e d ent i re ly . In o r d e r t o m a k e t h e task of se l ec t i on eas ier f o r t h e i ns t ruc to r , I have i nd i ca ted t h e /e\^e/ of difficulty after the name of each muscle, as f o l l o w s :

Levels 1 a n d 2—For b e g i n n i n g s t uden t s , in an i n t r o d u c t o r y c o u r s e w h e r e on l y o n e l abo ra to ry p e r i o d o r less is d e v o t e d t o t h e s t u d y of m u s c l e s .

Levels 3, 4, a n d 5—For m o r e a d v a n c e d s t u d e n t s , in an a n a t o m y c o u r s e in w h i c h t w o o r t h ree pe r i ods are d e v o t e d t o t h e d i s s e c t i o n of m u s c l e s .

Level 6—The i nd i v i dua l m u s c l e s of t h e f i n g e r s , f o r very a d v a n c e d (i.e. g radua te ) s t uden t s on ly . These m u s c l e s w i l l no t be e n c o u n t e r e d acc iden ta l l y in t h e sea rch f o r o t h e r musc les , a n d are c o n s i d e r e d b e y o n d t h e s c o p e of t h i s m a n u a l .

Ins t ruc to rs may n o w ( i ndeed , they should) i n f o r m the i r s t u d e n t s , fo r e x a m p l e , tha t they are requ i red t o learn t h e m u s c l e s of levels 1 , 2 a n d 3 on ly . S i nce al l t he musc les (excep t t h o s e o f t h e i nd i v i dua l f i ngers ) are l i s ted , t h e s t uden t w h o acc iden ta l l y f i nds a n o n r e q u i r e d m u s c l e d u r i n g d i ssec t i on s h o u l d be ab le t o co r rec t l y iden t i f y it f r o m t h e a p p r o p r i a t e d e s c r i p t i o n .

Sphinct ion, Di lat ion: S p h i n c t i o n is t h e c l o s i n g o r res t r i c t i ng of any o p e n i n g , cav i ty , o r h o l l o w s t ruc tu re . D i l a t i on is t h e e n l a r g i n g of any o p e n i n g , cav i ty , o r h o l l o w s t ruc tu re .

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18 A Labo ra to r y G u i d e t o F rog A n a t o m y

LABORATORY EXERCISES

D. MUSCLE TISSUES

If a d e q u a t e mate r ia l is ava i lab le , e x a m i n e s l ides o f t h e t h ree bas ic t ypes of m u s c l e t i ssue . Smooth muscle t issue is t h e s imp les t t ype , a n d s h o u l d be e x a m i n e d f i rs t . T h e ce l ls of t h i s t i ssue are usua l ly l o n g and s p i n d l e - s h a p e d , w i t h a n u c l e u s in t he center , s u r r o u n d e d by a la rge a m o u n t of c y t o p l a s m . S m o o t h m u s c l e t i ssue is i nvo lun ta ry , a n d it o c c u r s in t he m u s c u l a r l i n ings o f d iges t i ve a n d ce r ta in u rogen i t a l o r g a n s ( s t o m a c h , i n tes t ine , e tc . ; ov i duc t , u te rus , etc . ) , in t he l i n i ngs of a r ter ies , and in s u c h o the r l o c a t i o n s as t h e c i l ia ry b o d y of t h e eye, b u t never in musc les .

Cardiac muscle t issue, as its n a m e imp l ies , o c c u r s on l y in t h e hear t . No t i ce t ha t t h e f i be rs branch and anastomose ( re jo in , o f ten in a d i f f e ren t sequence) to f o r m a s ing le i n t e r c o n n e c t e d n e t w o r k . No t i ce a lso t h e interca­lated discs sepa ra t i ng t he ad jacen t ce l ls . Card iac m u s c l e t i ssue , l ike s m o o t h m u s c l e t i ssue , is i nvo lun ta ry , bu t in o the r respec ts it bears g rea te r re­s e m b l a n c e t o vo lun ta ry m u s c l e t i ssue : t h e nuc le i are pe r i phe ra l , a n d each f ibe r is s t r ong l y c r o s s b a n d e d .

Voluntary (also ca l led skeletal ) muscle t issue is cha rac te r i zed by t he p resence of n u m e r o u s para l le l b a n d i n g s o r cross-str iat ions, a f ea tu re w h i c h it shares w i t h ca rd iac musc le t i ssue . T h e nuc le i are l oca ted o n t he pe r i phe ry of each f iber , ra ther t h a n in t he cen ter . F u r t h e r m o r e , m a n y nuc le i o c c u r in t h e same f iber , w i t h no cel l b o u n d a r i e s sepa ra t i ng t h e m ; t h e f i be r is t h e r e f o r e ca l led a syncyt ium. In t he p resence of c ross -s t r i a t i ons a n d pe r i phe ra l n u c l e i , t he vo lun ta r y m u s c l e t i ssue resemb les ca rd iac m u s c l e t i ssue , bu t t he re are no in te rca la ted d iscs , a n d t h e f i be rs ne i the r b r a n c h nor a n a s t o m o s e . Un l i ke t he o the r t ypes of m u s c l e t i ssue , vo l un ta r y m u s c l e t i ssue is u n d e r t h e c o n s c i o u s , vo lun ta ry c o n t r o l of t he cen t ra l ne rvous s y s t e m ; i n d e e d , it is t h e on l y t i ssue of t he b o d y w h o s e a c t i o n s can be c o n t r o l l e d at w i l l . Un l i ke t h e o t h e r t w o types of m u s c l e t i ssue , w h i c h never o c c u r in musc les , th i s t i ssue t ype is confined t o musc les .

The vo lun ta ry musc les of t he b o d y c o n t a i n c o n n e c t i v e t i ssue in a d d i t i o n t o vo lun ta ry m u s c l e t i ssue. T h e p r e d o m i n a n t c o n n e c t i v e t i ssue in musc les is k n o w n as regular connect ive t issue because of i ts para l le l o r i e n t a t i o n of f i be rs , p r i nc ipa l l y of t h e p ro te i n co l lagen. Regu la r c o n n e c t i v e t i ssue sur­r o u n d s g r o u p s of para l le l m u s c l e f i be rs , a r r a n g i n g t h e m in to p r ima ry , seconda ry , te r t ia ry , and h i ghe r o rde r b u n d l e s . These layers of c o n n e c t i v e t i ssue are c o n t i n u o u s w i t h each o ther , a n d w i t h t he t e n d o n or a p o n e u r o s i s , if any ex is ts . They are a lso c o n t i n u o u s w i t h t he c o n n e c t i v e t i ssue of w h a t e v e r t h e m u s c l e may be a t t ached t o : t h e p e r i o s t e u m of a b o n e (never t h e b o n e t i ssue i tsel f ) , t he sc le ra of t h e eyeba l l , o r t h e d e r m i s of t h e s k i n . E x a m i n e a s l ide of a t e n d o n , a n d , if poss ib le , a lso of w h o l e musc les cu t in c ross sec t i on (s tudy unde r l ow p o w e r t h e a r r a n g e m e n t of t h e m u s c l e f ibe rs i n to bund les ) , a n d of t e n d i n o u s a t t a c h m e n t s t o bones .

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M u s c u l a r Sys tem 19

F. MUSCLES OF THE SPINAL COLUMN, TRUNK, AND ABDOMINAL WALL

L ike t h e g rea t ly c o m p a c t e d t r u n k ske le ton of t h e f r o g , t h e t r u n k musc les of t h e f r o g are g rea t ly r e d u c e d , espec ia l l y in s ize. W i t h t h e f o r e s h o r t e n i n g of t he sp ina l c o l u m n a n d t h e s t r e n g t h e n i n g of t h e i nd i v i dua l ve r teb rae , t h e sp ina l musc les in pa r t i cu la r have b e c o m e shor te r , s tou te r , a n d r e d u c e d in b o t h n u m b e r a n d c o m p l e x i t y . W i t h t h e loss of t h e r ibs , m a n y m u s c l e s o f t h e t r u n k reg ion have been lost , bu t t h e m u s c l e s o f t h e a b d o m i n a l wa l l have rema ined m o r e o r less u n s p e c i a l i z e d . Cer ta in sp ina l m u s c l e s have, as in

Ε. HOW TO DISSECT MUSCLES

Be fo re y o u b e g i n d i s s e c t i n g , m a k e su re y o u have read t h e i n t r o d u c t o r y pa rag raphs , A - C , above . Y o u may at t h i s t i m e w i s h t o re read p a r a g r a p h Β ( t e r m i n o l o g y of m o v e m e n t ) , as we l l as t h e d i r e c t i o n a l t e r m s o n pages x i i - x i i i of th i s m a n u a l .

Be fo re d i s s e c t i n g t h e m u s c l e s in any reg ion of t h e b o d y , l i f t away t h e sk i n in tha t reg ion by s l i d i ng t he b a c k e n d of y o u r sca lpe l o r f o r c e p s b a c k a n d f o r t h unde r t h e s k i n . Cu t t he sk in w i t h a sca lpe l o r w i t h sc i sso rs . Cu t a r o u n d (p re fe rab ly w i t h a sca lpe l ) , and leave t h e sk in a d h e r i n g t o , t h e f o l l o w i n g r e g i o n s : m o u t h , eye, t y m p a n u m , anus , h a n d (manus) , a n d f o o t (pes) .

W i t h a f i ne f o r c e p s , c lean away any c o n n e c t i v e t i ssue fasc ia w h i c h may s u r r o u n d each musc le . Pay pa r t i cu la r a t t e n t i o n t o t h e d i r e c t i o n of t h e m u s c l e f i be rs ; y o u may r e c o g n i z e m a n y i nd i v i dua l m u s c l e s in t h i s m a n n e r . Sepa ra te t he va r i ous musc les as best y o u c a n , us i ng blunt instruments only. (Do no t o v e r l o o k t h e po ten t ia l i t i es of t h e b a c k e n d , i.e. t h e h a n d l e , of y o u r sca lpe l o r f o r c e p s as a b l u n t i ns t rumen t . ) Sepa ra te t h e musc les as far as t he i r o r i g i n s and inse r t i ons , then iden t i f y t h e m w i t h t he a id of t h e d e s c r i p t i o n s a n d t h e i l l us t ra t ions . (F ind t h e m u s c l e first, then l o o k f o r i ts m a t c h i n g desc r i p t i on . )

W h e n d i ssec t i ng t he musc les , refer c o n t i n u a l l y t o (1) t h e m u s c l e d e s c r i p ­t i ons , (2) t h e a c c o m p a n y i n g d i a g r a m s , a n d (3) t h e m o u n t e d f r o g s k e l e t o n . Do not rely too heavily on illustrations for the identification of muscles; pos i t i ve i den t i f i ca t i on of musc les can be m a d e only by e x a m i n i n g the i r o r i g i n s a n d inse r t i ons , a n d c o m p a r i n g w i t h t h e a c c o m p a n y i n g d e s c r i p t i o n s (o r w i t h a char t l i s t ing o r i g i n s a n d inser t ions ) . If y o u m u s t cu t t h e ove r l y i ng m u s c l e s in o rde r t o s tudy t he u n d e r l y i n g ones , l i f t t h e m u s c l e in t h e m i d d l e of i ts be l ly (never at i ts o r i g i n or inser t ion ) a n d c u t c lean ly t h r o u g h w i t h a s h a r p sca lpe l (not sc issors) . If y o u mus t cu t severa l para l le l m u s c l e s , cu t each at a d i f f e ren t l e n g t h , so tha t y o u can r e c o n s t r u c t t h e c u t e n d s w i t h o u t e r ro r . D o not cut anything unless necessary, a n d c u t on l y in a m a n n e r t ha t w i l l a l l o w y o u t o p iece t h i n g s b a c k t o g e t h e r t h e way they w e r e . Use blunt tools wherever possible, t o avo id d a m a g i n g o the r m u s c l e s .

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20 A L a b o r a t o r y G u i d e t o F rog A n a t o m y

o the r land ver tebra tes , b e c o m e s e c o n d a r i l y a t t ached t o t h e s h o u l d e r g i r d l e ; these i n c l u d e t h e ser ra tus , r h o m b o i d e u s , a n d levator s capu lae m u s c l e s .

T h e epax ia l muscles {extensor muscles) of t h e sp ina l c o l u m n i n c l u d e t h e f o l l o w i n g (Nos. 1-5):

1 . Μ. coccygeosacra l ls ( level 3, F ig . 10). Th i s m u s c l e may be f o u n d do rsa l t o a n d b e t w e e n t h e l o n g i s s i m u s do rs i a n d c o c c y g e o i l i a c u s musc les . Its o r i g i n is f r o m t h e an te r i o r hal f o f t h e u ros ty le o n its la tera l aspec t . F r o m here , t he f i be rs run an te ro la te ra l l y , t o inser t u p o n t he t ransverse p rocess of t he n i n t h or sacra l ve r teb ra . T h e m u s c l e f u n c t i o n s t o f i x t he u ros ty le in p lace , a n d t o m o v e it do rsa l l y or t o e i ther s ide .

2. M. longissimus dorsi ( level 3, F ig . 10). Th i s l o n g , n a r r o w m u s c l e w i l l be f o u n d d o r s o m e d i a l l y , l y ing para l le l t o e i the r s i de o f t h e ve r teb ra l c o l u m n , a n d immed ia te l y b e n e a t h t h e dorsal fascia w h i c h cove rs t h e en t i re epax ia l m u s c u l a t u r e . T h e m u s c l e f i be rs o r i g i n a t e as far cauda l l y as t he an te r i o r t h i r d of t h e u ros ty le , a n d inser t as far c ran ia l l y as t he e x o c c i p i t a l b o n e of t h e sku l l . A l o n g its l e n g t h , t h e m u s c l e is in ter­rup ted by severa l t e n d i n o u s i n s c r i p t i o n s , each of w h i c h is a t t a c h e d t o t h e neura l a r ch a n d t ransverse p rocesses of an u n d e r l y i n g ve r teb ra . Th i s m u s c l e is t h e p r i n c i p a l e x t e n s o r m u s c l e o f t h e sp ina l c o l u m n ; t h e f ibe rs o f e i t he r s ide may ac t a l one t o a b d u c t o r a d d u c t t h e sp ina l c o l u m n dorso la te ra l l y .

3. M. i leolumbaris ( level 4 , F ig . 10). Th i s m u s c l e is d iv i s ib le in to a pars lateralis a n d a pars medialis. T h e pars medialis o r i g i na tes la rge ly f r o m t h e t ransverse p rocess of t h e n i n t h or sacra l ve r teb ra , c o n t i n u i n g an te r io r l y w h e r e t he m. c o c c y g e o s a c r a l i s leaves off . T h e pars lateralis has a t e n d i n o u s o r i g i n f r o m t h e la tera l s ide o f t h e i l i u m , f r o m w h e n c e it runs an te r i o r l y t o j o i n t h e pars medialis at t h e level o f t h e seven th ve r teb ra . F r o m here , t h e un i f i ed m u s c l e c o n t i n u e s an te r io r l y , t o inser t o n t h e t ransverse p rocess of t h e f o u r t h o r f i f t h ve r teb ra . Th i s m u s c l e is c o n t i n u e d f u r t he r an te r io r l y by p o r t i o n s of t h e m. l o n g i s s i m u s d o r s i , a n d , l ike t he lat ter, it is i n t e r r up ted severa l t i m e s by t e n d i n o u s i nsc r i p t i ons a n c h o r e d t o t he u n d e r l y i n g ve r teb rae . T h e m u s c l e ac ts as an ex tensor , a b d u c t o r , a n d h o m o l a t e r a l ro ta to r of t h e back .

4 . M m . intercrurales ( level 5, F ig . 22). These s h o r t m u s c l e s l ie d e e p t o t h e m. l o n g i s s i m u s d o r s i , w h e r e they run b e t w e e n t h e neu ra l a r c h e s of ad jacen t ve r teb rae . T h e a n t e r i o r m o s t of these m u s c l e s runs f o r w a r d f r o m the at las t o inser t o n t h e s k u l l , j us t above t h e f o r a m e n m a g n u m . T h e m u s c l e is an ex tenso r of t h e back .

5. M m . intertransversari i ( level 5, F igs. 10, 15, 22). These m u s c l e s run be tween t he t ransverse p rocesses of ad jacen t ve r teb rae as fa r a n ­te r io r l y as t h e s e c o n d , a n d f r o m t h e s e c o n d (no t t h e f i rs t ) ve r t eb ra t o t h e e x o c c i p i t a l b o n e of t h e s k u l l . The re are t w o pa i rs of t hese m u s c l e s

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b e t w e e n t h e sku l l a n d t h e s e c o n d ve r teb ra , a n d a lso b e t w e e n t h e s e c o n d a n d t h i r d ve r teb rae ; pos te r i o r t o t h e t h i r d ve r teb ra , t he re is on ly o n e pa i r of i n te r t ransversar i i per s e g m e n t . At v a r i o u s p laces , these m u s c l e s may be c lose ly assoc ia ted (or o c c a s i o n a l l y fused) w i t h t h e deep f i be rs o f t h e l onge r epax ia l m u s c l e s , s h o w i n g t ha t al l are c lose ly re la ted d e v e l o p m e n t a l l y . T h e in te r t ransversar i i are p r imar i l y a b d u c t o r musc les of t h e sp ina l c o l u m n .

T h e r e m a i n i n g musc les of t h e sp ina l c o l u m n a n d t r u n k are al l hypaxia l muscles, w h o s e p r im i t i ve f u n c t i o n lay in t h e f l e x i o n of t h e ve r teb ra l c o l u m n a n d t h e b o d y as a w h o l e . W i t h t h e f o r e s h o r t e n i n g of t h e ve r teb ra l c o l u m n and t he loss of r ibs , m a n y of these m u s c l e s have d i s a p p e a r e d , b u t a f ew st i l l r ema in , usua l ly w i t h a l te red f u n c t i o n s . Of t h e hypax ia l m u s c l e s st i l l p resen t in t he f r o g , o n e (No. 6) is n o w assoc ia ted w i t h t h e pe lv ic g i rd le , a n d seven (Nos. 7-13) w i t h t h e pec to ra l g i rd le . T h e r e m a i n i n g f ive hypax ia l m u s c l e s (Nos. 14 -18 ) have lost al l c o n n e c t i o n w i t h t h e ve r teb rae a n d r i bs ; f o u r are assoc ia ted w i t h t he ven t ra l a b d o m i n a l w a l l , w h i l e t h e last has b e c o m e spec ia l i zed as an ana l sph inc te r .

6. M. coccygeoi l iacus ( level 3, F igs. 10, 18). Th i s b r o a d m u s c l e l ies an te r i o r t o t h e c l oaca , o n e i the r s ide o f t h e do rsa l m i d l i n e . Its o r i g i n is f r o m the u ros ty le , a l o n g t h e g rea te r par t of i ts en t i r e l e n g t h . F r o m here , t h e f i be rs run an te ro la te ra l l y , t o inser t o n t h e an te r i o r t w o - t h i r d s o f t he i l i u m . T h e m o r e an te r i o r f i be rs are c o v e r e d med ia l l y by t h e c o c c y g e o s a c r a l i s m u s c l e . T h e m. c o c c y g e o i l i a c u s f u n c t i o n s as an a d d u c t o r a n d re t rac to r of t h e i l i u m ; it a lso he lps h o l d t h e u ros ty le in p lace .

7. M. rhomboideus anter ior ( level 4, F igs. 1 0 , 1 5 ) . A f lat m u s c l e , par t ia l l y h i d d e n by t h e s u p r a s c a p u l a . Its o r i g i n is f r o m t h e p o s t e r i o r e n d of t h e f r o n t o p a r i e t a l b o n e , near t he p o s t e r o m e d i a l c o r n e r o f t h e m. t e m ­pora l i s . T h e i nse r t i on is t o t h e deep or ven t ra l su r f ace of t he s u p r a s c a p u l a near its med ia l b o r d e r ; t h e m m . r h o m b o i d e u s pos te r i o r , levator scapu lae supe r i o r , a n d se r ra tus s u p e r i o r a lso inser t in th i s r eg i on . The m. r h o m b o i d e u s an te r i o r s h o u l d be cu t , a n d t h e s h o u l d e r g i rd le f o l d e d pos te ro la te ra l l y , in o r d e r t o e x p o s e these m u s c l e s . T h e m. r h o m b o i d e u s an te r i o r f u n c t i o n s p r i nc i pa l l y as a p r o t r a c t o r of t h e s h o u l d e r g i rd le .

8. IVI. rhomboideus posterior ( level 5, F igs. 10 ,15 ) . T h i s b r o a d , f la t , t r i a n ­gu la r m u s c l e o r i g i na tes f r o m t h e neura l sp ines of t h e t h i r d a n d f o u r t h ve r teb rae , f r o m t h e t ransverse p rocess of t h e f o u r t h ve r teb ra , a n d f r o m t h e t e n d i n o u s s e p t u m tha t l ies b e t w e e n these , in assoc ia t i on w i t h t h e m. l o n g i s s i m u s d o r s i . F r o m here , t h e f i be rs c o n v e r g e an te r i o r l y t o w a r d a sho r t t e n d o n , by w h i c h t he m u s c l e inser ts o n t h e deep o r ven t ra l su r f ace of t he s u p r a s c a p u l a near i ts med ia l bo rde r , j us t

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pos te r i o r t o t he inse r t i on of t h e m. r h o m b o i d e u s an te r io r . T h e p r ima ry f u n c t i o n o f t h i s m u s c l e is t ha t of a re t rac to r o f t h e s h o u l d e r g i r d l e ; it a lso f u n c t i o n s , t o g e t h e r w i t h t h e o the r musc les in th i s r e g i o n , t o a t t ach t h e s h o u l d e r g i r d l e t o t h e ax ia l s k e l e t o n .

9. M. levator scapu lae superior ( level 5, F igs. 1 0 , 1 5 ) . T h e o r i g i n of t h i s m u s c l e is f r o m the p r o o t i c a n d e x o c c i p i t a l b o n e s of t h e s k u l l , j us t ven t ra l a n d pos te r i o r t o t he ear r e g i o n , a n d sepa ra ted by t he t e m p o r a l i s m u s c l e f r o m t h e o r i g i n of t h e m. r h o m b o i d e u s an te r i o r ; a sma l l n u m b e r o f f i be rs a lso o r i g i n a t e d i rec t l y f r o m t h e t y m p a n i c ca r t i l age . T h e m u s c l e t h e n runs pos te r io r l y , t o inser t o n t h e deep o r ven t ra l su r f ace of t h e s u p r a s c a p u l a near i ts m e d i a l bo rde r , j us t an te r i o r t o t h e i nse r t i on of t h e m. r h o m b o i d e u s an te r io r . Th i s m u s c l e ac ts t o p ro t r ac t t he s h o u l d e r g i r d l e , a n d t o a b d u c t t h e head t o w a r d t h e same s ide .

10. M. levator scapu lae inferior ( level 5, F igs. 10, 15). Th i s m u s c l e o r i g i ­nates a l o n g a gen t l y c u r v e d , c i r cu la r arc , f r o m t h e en t i re w i d t h of t h e e x o c c i p i t a l b o n e a l o n g its ven t ra l m a r g i n , e x c l u d i n g t h e m e d i a l m o s t p o r t i o n b e t w e e n t h e t w o o c c i p i t a l c o n d y l e s . T h e m u s c l e r u n s pos t ­e ro la te ra l l y u n d e r n e a t h t h e s u p r a s c a p u l a , f ina l l y i nse r t i ng o n t he ven t ra l su r f ace of t h i s ca r t i l age , near i ts pos te r i o r m a r g i n , la tera l t o t h e m. ser ra tus m e d i u s i nse r t i on . T h e m u s c l e ac ts t o p ro t r ac t t h e s h o u l d e r g i rd le .

1 1 . IVI. serratus superior ( level 5, F igs. 10 ,15 ) . Th i s l o n g , s l ende r m u s c l e o r i g i na tes f r o m t h e t ransverse p rocess of t he f o u r t h ve r teb ra . F r o m here it r uns an te romed ia l l y , a l o n g t h e la tera l m a r g i n o f t h e m. r h o m b o i d e u s pos te r i o r (w i th w h i c h it may s o m e t i m e s be par t ia l l y fused) , t o inser t a l o n g s i d e t h e la t ter m u s c l e o n t h e d e e p o r ven t ra l su r face of t he s u p r a s c a p u l a , near i ts med ia l m a r g i n , a n d jus t pos te r i o r t o t h e i nse r t i on of t h e m. r h o m b o i d e u s an te r io r . T h e m u s c l e ac ts t o re t rac t a n d a b d u c t t he s h o u l d e r g i r d l e , a n d t o d r a w it c loser t o t h e ve r teb ra l c o l u m n .

12. M. serratus medius ( level 5, F igs. 1 0 , 1 5 ) . Th i s sho r t b u t s t ou t m u s c l e is c o m p l e t e l y h i d d e n benea th t he s u p r a s c a p u l a . It o r i g i na tes f r o m t h e t ransverse p rocess of t h e t h i r d ve r teb ra , a n d a lso t o s o m e e x t e n t f r o m a t e n d i n o u s a rch c o n n e c t i n g th i s w i t h t h e t ransverse p rocess of t h e f o u r t h ve r teb ra . F r o m here it r ises dorsa l l y , t h o u g h i nc l i ned a n t e r o m e ­d ia l ly , t o inser t on t he ven t ra l su r f ace of t h e s u p r a s c a p u l a , a l o n g an arc w h i c h l ies jus t lateral t o t h e i nse r t i ons of t h e se r ra tus supe r i o r , r h o m b o i d e u s an te r io r a n d pos te r io r , a n d levator s c a p u l a e an te r i o r musc les . T h e m u s c l e ac ts t o depress t h e s h o u l d e r g i rd le , a n d t o d r a w it c loser t o t h e ve r teb ra l c o l u m n .

13. M. serratus inferior ( level 5, F igs. 10 ,15) . Th i s l o n g m u s c l e o r i g i n a t e s in t w o p o r t i o n s , f r o m t h e t ransverse p rocesses of ve r teb rae 3 a n d 4. B o t h p o r t i o n s t h e n run latera l ly a n d s l i gh t l y an te r io r l y , as they c o n v e r g e

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w i t h each o the r t o inser t o n t h e med ia l o r i nner su r f ace of t h e s c a p u l a (not t h e sup rascapu la ) , a l o n g its pos te r i o r m a r g i n , s o m e w h a t ven t ra l t o t h e i nse r t i on of t he m. levator s c a p u l a e in fe r io r . T h e m u s c l e ac ts t o a d d u c t t h e s h o u l d e r g i rd le , a n d t o d r a w it c loser t o t h e ve r teb ra l c o l u m n .

T h e f o l l o w i n g f o u r musc les (Nos. 14 -17 ) s u p p o r t t h e ven t ra l a b d o m i n a l w a l l , h o l d i n g in t h e v i sce ra a n d p r e v e n t i n g the i r s a g g i n g o u t f r o m t h e a b d o m i n a l cav i ty . A l l f o u r are ex t reme ly b r o a d a n d shee t l i ke , a n d can be mos t easi ly d i s t i n g u i s h e d by t h e d i r e c t i o n of t he i r f i be rs .

14. M. cu taneus abdominis ( level 3, F ig . 10). T h i s n a r r o w m u s c l e o r i g i na tes f r o m t h e c a r t i l a g i n o u s pub i s , deep ly b u r i e d in t h e pe lv ic r e g i o n . F r o m here , t h e f i be rs pass la tera l ly a n d t h e n do rsa l l y d i v e r g i n g as they reach a r o u n d t h e la tera l s ide of t h e m. t e n s o r fasc iae latae, a n d f ina l ly a c h i e v i n g i nse r t i on t o t h e d e r m i s of t h e sk in in t h e reg ion ove r l y i ng t he i l i um a n d t h e space b e t w e e n i l i um a n d u ros ty le . A l t h o u g h th i s m u s c l e f u n c t i o n s as a t enso r of t h e sk i n in t h i s r e g i o n , its i nne rva t i on s h o w s it t o be c lose ly re la ted t o t h e nex t t h ree musc les , w h i c h s u p p o r t t he a b d o m i n a l w a l l .

15. iVI. rectus abdominis ( level 1 , F igs. 11 ,12 ) . Th i s f la t m u s c l e is t h e m o s t super f i c i a l of t he musc les of t h e a b d o m i n a l w a l l ; i ts f i be rs run l ong i t ud ina l l y , pa ra l l e l i ng t he ven t ra l m i d l i n e o n e i the r s ide . T h e o r i g i n is f r o m t h e p u b i c symphys i s by m e a n s of a s t r o n g bu t n a r r o w t e n d o n , in c o m m o n w i t h t h e a b d o m i n a l i s p o r t i o n o f t h e pec to ra l i s m u s c l e . As t he m u s c l e passes f o r w a r d f r o m here , it is s u b d i v i d e d severa l t i m e s by a ser ies of transverse, tendinous inscriptions, a n d a lso by a w h i t e l ine , t h e l inea a lba, w h i c h runs a l o n g t he ven t ra l m i d l i n e t o separa te t h e r i gh t a n d left rec tus a b d o m i n i s musc les . T h e m u s c l e c o n t i n u e s an te r io r l y benea th t he s t e r n u m , w h e r e s o m e f ibe rs inser t o n the x i p h i s t e r n u m . T h e ma jo r i t y of f i be rs a t t ach t o o n e last t e n d i n o u s i n s c r i p t i o n , af ter w h i c h they c o n t i n u e as t h e s t e r n o h y o i d e u s m u s c l e (q.v.). T h e rec tus a b d o m i n i s m u s c l e s h o r t e n s t h e be l ly , s u p p o r t s t h e a b d o m i n a l o r g a n s , a n d d r a w s t h e s t e r n u m pos te r io r l y .

16. M. obl iquus externus ( level 1 , F igs . 10, 1 1 , 13). Th i s t h i n shee t of m u s c l e o r i g i na tes f r o m t h e i l i um a n d f r o m t h e fasc ia w h i c h covers t h e epax ia l musc les . F r o m here , i ts f i be rs pass o b l i q u e l y cauda l l y a n d vent ra l l y , t o inser t o n t h e a p o n e u r o s i s w h i c h i m m e d i a t e l y unde r l i es t he m. rec tus a b d o m i n i s . The ex te rna l o b l i q u e ac ts t o s u p p o r t t h e a b d o m i n a l o r g a n s , a n d t o d r a w the a b d o m i n a l wa l l an te r i o r l y w h i l e s t r e t c h i n g it t ransverse ly .

17. M. obl iquus internus ( level 1 , F igs. 10, 1 1 , 13). Th i s m u s c l e , a lso k n o w n as t h e m. t r ansve rsus a b d o m i n i s , is a t h i n sheet of m u s c l e , c lose ly app l i ed t o t h e p rev ious m u s c l e , b u t d i f f e r i ng in t h e d i r e c t i o n o f

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G. MUSCLES OF THE HEAD REGION

The musc les o f t h e head are as d iverse in de r i va t i on as t hey are in f u n c t i o n . The musc les of t he eye, and severa l of t h e h y o i d musc les , are de r i ved f r o m som i tes (b l ocks of m e s o d e r m ) , w h i l e t h e r e m a i n i n g musc les are der ived f r o m t h e f leshy i nves tmen t of t h e g i l l a r ches (see S e c t i o n J , b e l o w , f o r f u r t he r t r ea tmen t ) . T h e head c o n t a i n s s ix musc les assoc ia ted w i t h t he m o v e m e n t s of t he eyeba l l , f ive w i t h t he o p e n i n g a n d c l o s i n g of t h e j aws , a n d an even dozen w i t h t he m o v e m e n t s of t he t o n g u e , t h e f l o o r of t h e m o u t h , a n d t he hyo id appa ra tus . T w o r e m a i n i n g musc les , t h e m. c u c u l l a r i s a n d m. i n te rscapu la r i s , t h o u g h der i ved f r o m musc les of t he head , have b e c o m e assoc ia ted w i t h t h e m o v e m e n t s of t h e s h o u l d e r g i rd le .

Muscles of the Eyeball

The f o l l o w i n g s ix musc les are c o n c e r n e d w i t h t h e m o v e m e n t s of t h e eyeba l l . The f o u r rec tus musc les o r i g i na te t o g e t h e r in t he p o s t e r o m e d i a l co rne r of t he o rb i t , c lose t o t he o p t i c nerve ; t he s u p e r i o r a n d i n fe r i o r o b l i q u e musc les o r i g i na te in t h e a n t e r o m e d i a l c o r n e r of t h e o rb i t . A l l s ix m u s c l e s a t tach t o t he sc le ra of t h e eyeba l l .

19. M. rectus superior ( level 3, F ig . 15). Def lec ts t h e eyeba l l dorsa l l y . 20. IVI. rectus mediai is ( level 3, F ig . 15); a lso ca l led rec tus i n te rnus .

Def lec ts t h e eyebal l med ia l l y . 2 1 . IVI. rectus inferior ( level 3, F ig . 15). De f lec ts t h e eyeba l l ven t ra l l y . 22. M. obl iquus inferior ( level 3, F ig . 15). Runs ven t ro la te ra l l y , t o inser t

l ow o n t h e eyeba l l . Rota tes t h e eyeba l l la tera l ly .

its f ibe rs . F r o m an o r i g i n a l o n g t he i l i u m , t he do rsa l f asc ia (of t h e epax ia l musc les ) a n d t h e t ransverse p rocesses of t h e ve r teb rae , t h e f i be rs pass ob l i que l y an te r io r l y a n d ven t ra l l y , benea th t he a b d o m i n a l i s p o r t i o n of t h e pec to ra l i s musc le , t o inser t o n t h e an te r i o r p o r t i o n of t he s a m e a p o n e u r o s i s t o w h i c h the ex te rna l o b l i q u e a t taches .

18. M. sphincter ani ( level 2, F ig . 10). T h e f i be rs of t h i s m u s c l e enc i r c l e t h e anus . S o m e of t h e f i be rs d i ve rge t angen t i a l l y f r o m t h e rest t o run an te r io r l y and inser t u p o n t he pos te r i o r t i p of t h e u ros ty le . Th i s m u s c l e f u n c t i o n s as an anal sph inc te r .

In a d d i t i o n t o t h e musc les l is ted above , ce r ta in o the r m u s c l e s l ie in t h e t r u n k r eg i on . Of these , t he m. cucu l l a r i s is t rea ted u n d e r t h e m u s c l e s of t he head ( f rom w h i c h it is der ived) , w h i l e t h ree o the r musc les (m . la t i ss imus do rs i , m. pec to ra l i s , m. c u t a n e u s pec to r i s ) are de r i ved f r o m , a n d l is ted a m o n g , t he musc les of t h e pec to ra l g i r d le .

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23. Μ. obl iquus superior ( level 3, F ig . 15). R u n s do rso la te ra l l y , t o inser t h i gh on t he eyeba l l . Ro ta tes t h e eyeba l l med ia l l y .

24. M. rectus lateral is ( level 3, F ig . 15); a lso ca l led rec tus e x t e r n u s . De f lec ts t h e eyeba l l la tera l ly .

T h e f o l l o w i n g f ive musc les are assoc ia ted w i t h t h e m o v e m e n t s of t h e j aws . T h e f i rs t f o u r m u s c l e s ac t t o c lose t h e j aws , o r t o e levate t h e m a n d i b l e . T h e m. dep resso r m a n d i b u l a e , as its n a m e imp l i es , ac ts t o o p e n t h e j aws , o r t o depress t h e m a n d i b l e .

25. M. tempora l is ( level 1 , F igs. 10, 13, 15). Th i s s t r o n g m u s c l e o c c u p i e s m u c h of t h e space w i t h i n t h e o rb i t immed ia te l y pos te r i o r t o t h e eyeba l l . The ma jo r i t y of t h e f i be rs o r i g i n a t e f r o m t h e p r o o t i c and t h e ad jacen t par t of t he e x o c c i p i t a l bones , j us t med ia l t o t h e t y m p a n i c ca r t i l age ; a f ew f ibe rs a lso o r i g i n a t e d i rec t l y f r o m th i s ca r t i l age . T h e m u s c l e passes deep to t h e q u a d r a t o j u g a l a n d p t e r y g o i d bones , t o inser t o n t h e c o r o n o i d p r o c e s s of t h e m a n d i b l e . T h i s m u s c l e c loses a n d re t rac ts t he l ower j aw .

26. M. masseter major ( level 2, F igs. 13, 15). Th i s m u s c l e o r i g i na tes f r o m the an te roven t ra l q u a d r a n t of t h e t y m p a n i c ca r t i l age a l o n g its deep o r med ia l su r face , a n d a lso f r o m t h e ad jacen t an te r i o r l y p r o j e c t i n g zygomatic process o f t h e s q u a m o s a l b o n e . Its f i be rs pass supe r f i c i a l t o t he p t e r y g o i d a n d q u a d r a t o j u g a l b o n e s , t o inser t o n t h e ou te r o r la tera l su r f ace of t h e pos te r i o r p o r t i o n of t h e m a n d i b l e , i n c l u d i n g t h e c o r o n o i d p rocess . Th i s m u s c l e c loses a n d p r o t r a c t s t h e l owe r j aw .

27. M. masseter minor ( level 3, F igs. 13 ,15 ) . Th i s sma l l , t r i a n g u l a r m u s c l e o r i g i na tes f r o m t h e s q u a m o s a l (an te roven t ra l m a r g i n of t h e pos t -e roven t ra l l y p r o j e c t i n g f lange) a n d q u a d r a t o j u g a l ( la tera l su r face) bones near t h e j aw a r t i c u l a t i o n . F r o m the i r ra ther l oca l i zed o r i g i n , t h e f i be rs d i ve rge , t o inser t o n t h e la tera l su r f ace of t h e m a n d i b l e , j us t bes ide a n d pos te r i o r t o t h e i nse r t i on of t h e m. masse te r ma jo r . T h e an te r i o r p o r t i o n of t h e m. masse te r m i n o r is c o v e r e d by m. masse te r ma jo r ; t he m a n d i b u l a r b r a n c h of t h e f i f t h o r t r i g e m i n a l nerve may readi ly be f o u n d sepa ra t i ng t h e t w o m u s c l e s . T h e m. masse te r m i n o r c loses the j aws , and a lso a d d u c t s t h e pos te r i o r e n d of t h e m a n d i b l e lateral ly .

28. M. pterygoideus ( level 3, F ig . 15). Th i s m u s c l e l ies b e t w e e n t he m. t e m p o r a l i s a n d t h e eyeba l l . It o r i g i na tes f r o m t h e p r o o t i c a n d f r o n ­topa r ie ta l bones , a s s u m i n g a la tera l ly c o m p r e s s e d , f l a t t ened shape . T h e f ibe rs c o n v e r g e pos te roven t ro la te ra l l y , g i v i n g w a y t o a l o n g , t h i n t e n d o n w h i c h passes over t h e p t e r y g o i d a n d q u a d r a t o j u g a l b o n e s t o inser t u p o n t h e a n g u l o s p l e n i a l b o n e of t h e m a n d i b l e , j us t in f r o n t of t he j aw a r t i c u l a t i o n , a n d jus t pos te r i o r t o t h e m. t e m p o r a l i s i nse r t i on .

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Th is m u s c l e is a levator , p ro t rac to r , a n d con t ra la te ra l r o ta to r of t h e l ower j aw .

29. M. depressor mandibu lae ( level 1 , F igs. 10, 13, 15). Th i s la rge, t r i a n g u l a r m u s c l e has an ex tens ive o r i g i n f r o m t h e fasc ia ove r l y i ng t he epax ia l musc les a n d t h e m. t e m p o r a l i s , f r o m t h e p o s t e r o d o r s a l l y p r o j e c t i n g f l ange of t h e s q u a m o s a l , a n d f r o m the deep or med ia l su r face of t h e pos te r i o r p o r t i o n of t he t y m p a n i c ca r t i l age . F r o m here, t he f i be rs c o n v e r g e , pass ing b e h i n d t h e t y m p a n u m at t h e pos te r i o r l im i t of t h e sku l l , and par t ia l ly c o v e r i n g t he scapu la . T h e c o n v e r g i n g f i be rs inser t o n t o t h e e x t r e m e pos te r i o r e n d of t h e l o w e r j aw , b e h i n d t h e j aw a r t i cu l a t i on , w h e r e they serve t o depress t h e l owe r j aw a n d o p e n the m o u t h .

Muscles of the Tongue, the Floor of the Mouth, and the Hyoid Apparatus

30. M. mylohyoideus ( level 2, F igs. 1 1 , 1 2 , 23). Th i s musc le , a lso k n o w n as t h e m. submax i l l a r i s , is a b r o a d , f la t m u s c l e w h i c h spans t h e f l o o r of t h e m o u t h be tween t he t w o lower j aws . Its o r i g i n is f r o m t h e med ia l m a r g i n of t he l ower j aw a l o n g t he a n g u l o s p l e n i a l b o n e ; t h e i nse r t i on is t o a t e n d i n o u s raphe ( p r o n o u n c e d " r a - f a y " o r " r a - f e e " ) , s im i l a r t o t h e l inea a lba , w h i c h l ies in t he ven t ra l m i d l i n e . Th i s m u s c l e ac ts t o ra ise t he f l oo r of t h e m o u t h , a n d t h u s t o a id in b r e a t h i n g . Cu t t h i s m u s c l e t o o n e s ide of t he t e n d i n o u s raphe , in o rde r t o e x p o s e t h e u n d e r l y i n g musc les .

3 1 . M. subhyoideus ( level 3, F igs. 1 1 , 1 2 , 23). T h i s m u s c l e ar ises f r o m t h e l ong an te r io r c o r n u of t h e hyo id appa ra tus . F r o m here , it passes f i rs t ven t ra l l y and t h e n latera l ly , w h e r e it c o m e s t o l ie in para l le l w i t h , a n d jus t pos te r i o r t o , t h e f i be rs of t he m. m y l o h y o i d e u s ; t h e d i s t i n c t i o n be tween these t w o musc les may no t at f i rs t be appa ren t . T h e i nse r t i on is t o t h e s a m e t e n d i n o u s raphe t o w h i c h t h e m. m y l o h y o i d e u s a t taches .

32. M. submenta l is ( level 2, F ig . 12). Th i s sma l l m u s c l e l ies deep t o t h e m. m y l o h y o i d e u s . It cons i s t s of a sma l l n u m b e r of t ransverse ly o r i e n t e d f ibe rs , s p a n n i n g t h e m a n d i b u l a r s ymphys i s f r o m s ide t o s ide , b e t w e e n t h e m e n t o m e c k e l i a n bones . T h e m u s c l e s t r e n g t h e n s t h e m a n d i b u l a r symphys i s .

33. M. genioglossus ( level 4 , F ig . 12). Th i s sma l l m u s c l e l ies ad j acen t t o t h e p rev ious one , bu t i ts f i be rs are l o n g i t u d i n a l l y o r i e n t e d . T h e f i be rs o r i g i na te f r o m t h e m a n d i b u l a r symphys i s , f r o m w h i c h they pass pos te r io r l y , t h e n r e c u r v i n g do rsa l l y a n d t h e n an te r io r l y , t o en te r t h e s u b s t a n c e of t he t o n g u e a n d c o n t i n u e up t o i ts an te r i o r t i p . T h e m u s c l e re t rac ts t h e t i p of t h e t o n g u e .

34. M. hyoglossus ( level 3, F ig . 12). Th i s n a r r o w , u n p a i r e d m u s c l e l ies in t he ven t ra l m i d l i n e o n t h e f l o o r of t h e m o u t h , deep t o a n d b e t w e e n t h e

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r i gh t a n d left g e n i o h y o i d s . F r o m the i r o r i g i n o n t h e b o d y ( co rpus ) of t h e hyo id ca r t i l age , t h e f i be rs r un an te r io r l y , t u r n i n g do rsa l l y t o en te r t h e base of t h e t o n g u e , a n d t h e n s p r e a d i n g o u t t o rami f y in i ts s u b s t a n c e . T h e m u s c l e ac ts t o ach ieve v a r i o u s m o v e m e n t s of t h e t o n g u e , i n c l u d i n g t h e rap id p r o t r a c t i o n a n d eve rs ión so use fu l in t h e c a t c h i n g of insec ts .

35. M. gen iohyoideus ( level 2, F ig . 12). Th i s pa i red m u s c l e l ies t o e i t he r s ide of t h e ven t ra l m i d l i n e , c o v e r i n g t h e p rev i ous m u s c l e , a n d u n d e r t h e cover of t h e m. m y l o h y o i d e u s . T h e f i be rs o r i g i n a t e f r o m t h e m a n d i b l e , in t he reg ion of t h e m a n d i b u l a r s y m p h y s i s ; f r o m here they pass d i rec t l y pos te r io r l y , f i na l l y d i v i d i n g in to a la rger med ia l p o r t i o n , w h i c h inser ts o n t o t h e c o r p u s of t h e h y o i d ca r t i l age , a n d a sma l l e r la tera l p o r t i o n , w h i c h inser ts o n t he pos te r i o r c o r n u . T h e m u s c l e pu l l s t h e h y o i d f o r w a r d .

36. M. s ternohyoideus ( level 2, F ig . 12). Th i s e l o n g a t e d m u s c l e o r i g i n a t e s f r o m t h e s t e r n u m , f r o m t h e a d j a c e n t p o r t i o n of t h e c o r a c o i d b o n e , a n d f r o m the m. rec tus a b d o m i n i s w i t h t h e i n t e r ven t i on of a t e n d i n o u s i n s c r i p t i o n . Pass ing deep t o t h e c o r a c o i d a n d c lav ic le , t h i s m u s c l e r uns an te r io r l y , t o inser t on t h e c o r p u s of t h e h y o i d ca r t i l age , w h e r e i ts f i be rs i n t e r m i n g l e w i t h t h o s e of t h e m. g e n i o h y o i d e u s . It d r a w s t h e h y o i d pos te r io r l y .

37. M. omohyoideus ( level 3, F ig . 12). Th i s m u s c l e o r i g i n a t e s f r o m t h e inner s ide of t h e s c a p u l a near i ts pos te r i o r bo rde r , a n d r u n s a n t e r o m e -d ia l ly to inser t o n t he ven t ra l su r f ace of t h e c o r p u s of t h e hyo id ca r t i l age . Po r t i ons of t h i s m u s c l e l ie u n d e r t h e cove r of t h e m. s t e r n o h y o i d e u s a n d m. g e n i o h y o i d e u s . T h e m u s c l e d r a w s t h e s c a p u l a an te romed ia l l y , and t h e h y o i d ca r t i l age pos te r i o r l y a n d la tera l ly .

38. M. petrohyoideus anter ior ( level 4, F igs. 12 ,23 ,33 ) . Th i s f la t , t r i a n g u l a r m u s c l e o r i g i na tes f r o m a res t r i c ted area o n t he p r o o t i c b o n e of t he sku l l , ad jacen t t o t h e t y m p a n i c ca r t i l age . F r o m here , it b r o a d e n s o u t as it w r a p s a r o u n d ven t ra l l y a n d t h e n med ia l l y , t o inser t la tera l ly on t he ven t ra l su r face of t h e h y o i d c o r p u s . The m u s c l e f u n c t i o n s as a c o n s t r i c t o r of t he pha rynx .

3 9 . - 4 1 . IVIm. petrohyoidei poster iores I, I I , and III ( level 4, F igs. 12 ,23 ,33 ) . These th ree l o n g , t h i n m u s c l e s o r i g i n a t e t oge the r , j us t p o s t e r i o r t o t he m. p e t r o h y o i d e u s an te r io r , in t he r e g i o n jus t above a n d b e h i n d t he ear, la rge ly f r o m t h e p r o o t i c b o n e of t h e s k u l l . F r o m here , they pass ven t ra l l y a n d d i ve rge , i nse r t i ng separa te ly o n t h e pos te r i o r o r t h y r o i d c o r n u of t h e h y o i d a p p a r a t u s : m. p e t r o h y o i d e u s pos te r i o r I near t h e base of t h e c o r n u , m. p e t r o h y o i d e u s pos te r i o r 11 in t he m i d d l e of t he c o r n u , a n d m. p e t r o h y o i d e u s p o s t e r i o r III near its t i p . Al l t h ree musc les are i m p o r t a n t in t h e ac t of s w a l l o w i n g .

The f o l l o w i n g t w o m u s c l e s are assoc ia ted w i t h t h e m o v e m e n t s of t h e

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28 A Labo ra to r y G u i d e t o F rog A n a t o m y

H. MUSCLES OF THE SHOULDER GIRDLE AND FORELIMB

Lis ted b e l o w are t h e t r u e a p p e n d i c u l a r musc les of t h e s h o u l d e r g i r d l e a n d f o r e l i m b (see S e c t i o n J , be low) . In a d d i t i o n t o these , ce r ta in o t h e r m u s c l e s w h i c h l ie in t h e reg ion of t h e s h o u l d e r g i r d l e have a l ready been d e s c r i b e d : t h e r h o m b o i d , se r ra tus , a n d levator s capu lae musc les (Nos. 7-13) a m o n g t h e t r u n k musc les , a n d t h e c u c u l l a r i s a n d i n te rscapu la r i s (Nos. 4 2 - 4 3 ) a m o n g t h e musc les of t h e h e a d , f r o m w h i c h they are de r i ved .

Dorsal (Extensor) Muscles of the Shoulder

44. M. lat issimus dorsi ( level 1 , F igs, 1 0 , 1 3 , 1 5 ) . Th i s f an - shaped m u s c l e o r i g i na tes f r o m t h e deep su r face of t he do rsa l a p o n e u r o s i s w h i c h over l ies t h e epax ia l m u s c l e s o f t h e back , a l o n g a c i r c u l a r a rc w h i c h runs f r o m the level of t h e t h i r d ve r teb ra pos te r i o r l y a n d t h e n la tera l ly t o t he level of t h e f i f t h or s i x th ve r teb ra . F r o m th i s o r i g i n , t h e m u s c l e f i be rs c o n v e r g e as t hey pass an te ro la te ra l l y , par t ia l l y c o v e r i n g t h e p o s t e r i o r

s h o u l d e r g i rd le , bu t t he i r i nne rva t i on by t he v a g u s nerve (a c ran ia l nerve) be t rays t h e fac t tha t they are de r i ved f r o m t h e h e a d . T h e m. c u c u l l a r i s no t on ly shares a c o m m o n i nne rva t i on w i t h t h e pos te r i o r p e t r o h y o i d m u s c l e s , bu t its p r o x i m a l p o r t i o n is s t i l l in s e q u e n c e w i t h these .

42. M. cucullaris ( level 3, F igs. 10 ,15 ,23) . Th i s m u s c l e , c o r r e s p o n d i n g t o t he t r apez ius a n d s t e r n o c l e i d o m a s t o i d e u s musc les of m a m m a l s , takes o r i g i n f r o m the head , in s e q u e n c e w i t h t h e pos te r i o r p e t r o h y o i d musc les , bu t inser ts o n t h e s h o u l d e r g i r d l e . It ar ises f r o m t h e p r o o t i c a n d e x o c c i p i t a l b o n e s near t he i r j u n c t i o n , u n d e r t h e cove r of t he m. dep resso r m a n d i b u l a e . F r o m here , it passes pos te roven t ra l l y t o inser t o n the deep or med ia l su r f ace of t h e s c a p u l a near i ts a n t e r i o r bo rder , b e t w e e n t h e m. i n te rscapu la r i s a n d t h e scapu la r p o r t i o n of t he m. de l t o i deus . T h e cucu l l a r i s d r a w s t h e s h o u l d e r g i r d l e c ran ia l l y and med ia l l y , a n d t h e head pos te roven t ra l l y , r o ta t i ng it a lso con t ra la te ra l l y .

43. IVI. interscapular is ( level 5, F ig . 15). Th i s d e e p , t r i a n g u l a r m u s c l e l ies o n t h e deep or inner su r face of t h e s h o u l d e r g i rd le . Its b r o a d o r i g i n is c o n f i n e d t o t he ven t ra l hal f of t he s u p r a s c a p u l a a l o n g its an te r i o r t w o - t h i r d s , at t he level w h e r e t he m. levator s capu lae in fe r io r inser ts . F rom here , i ts f i be rs c o n v e r g e med ia l l y t o a po in t , c r o w d i n g the i r w a y be tween t h e m. d e l t o i d e u s a n d t h e m. c o r a c o b r a c h i a l i s b rev is , a n d inse r t i ng o n t o t he same r i dge o n t he deep su r face of t h e s c a p u l a f r o m w h i c h these lat ter t w o musc les o r i g i na te . T h e m u s c l e dec reases t h e ang le b e t w e e n t he s c a p u l a a n d s u p r a s c a p u l a .

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m a r g i n of t h e scapu la a n d i ts m u s c u l a t u r e . T h e f i be rs t h e n inser t u p o n a f la t t e n d o n , w h i c h fuses w i t h t h e t e n d o n of t h e m. do rsa l i s scapu lae be fo re i nse r t i ng o n t h e la tera l s ide o f a c res t , w h i c h runs a l o n g t h e ven t ra l s ide of t h e h u m e r u s . T h e m. la t i ss imus do rs i is an e x t e n s o r (or a b d u c t o r ) of t he h u m e r u s , a n d a lso a re t rac to r of t h e same .

45. M. dorsal is scapu lae ( level 3, F igs . 1 0 , 1 3 , 1 5 ) . T h i s b r o a d , t r i a n g u l a r m u s c l e covers t h e ma jo r i t y of t h e s h o u l d e r g i r d l e ; i ts an te r i o r b o r d e r is in t u r n cove red by t he m. dep resso r m a n d i b u l a e , a n d its pos te r i o r b o r d e r by t h e m. la t i ss imus d o r s i . Its o r i g i n is a l o n g a s l i gh t l y cu r ved l ine, para l le l t o t h e ve r teb ra l c o l u m n , a n d e x t e n d i n g ac ross t h e an te r i o r t w o - t h i r d s of t h e s u p r a s c a p u l a , l eav ing i ts m e d i a l m o s t p o r t i o n u n c o ­ve red . F r o m here , t he f i be rs c o n v e r g e la tera l ly u p o n a f la t t e n d o n , w h i c h fuses w i t h t he t e n d o n of t h e m. l a t i ss imus do rs i be fo re i nse r t i ng o n t h e latera l s ide of a c res t r u n n i n g a l o n g t h e ven t ra l s ide o f t h e h u m e r u s . T h e m. do rsa l i s s c a p u l a e is an e x t e n s o r ( abduc to r ) a n d a med ia l r o ta to r o f t h e h u m e r u s .

46. M- del to ideus ( level 2, F igs. 10, 1 1 , 13, 14). Th i s m u s c l e , a s t r o n g p r o t r a c t o r of t he h u m e r u s , is d i v i s ib le in to t h ree d i s t i n c t p o r t i o n s :

Pars episternalis. T h e ep i s te rna l p o r t i o n of t h e d e l t o i d m u s c l e is l ong a n d t h i n . It r uns f r o m t h e m a r g i n of t h e e p i s t e r n u m a n d o m o s t e r n u m t o inser t , a l o n g w i t h hal f of t h e pars scapularis, on t he u lna r e p i c o n d y l e at t he d is ta l e n d of t h e h u m e r u s .

Pars clavicularis. T h e c lav i cu la r p o r t i o n is very sma l l , a n d runs f r o m t h e la tera l e n d of t h e c lav ic le t o a c res t ( s o m e t i m e s ca l l ed t h e d e l t o i d r idge) tha t runs a l o n g t h e ven t ra l s ide of t h e h u m e r u s , i nse r t i ng o n t h e p r o x i m a l hal f of t h i s c res t f r o m t h e med ia l o r an te r i o r s ide .

Pars scapularis. T h e s c a p u l a r p o r t i o n is by far t h e s t r o n g e s t par t of t h e d e l t o i d musc le . Its o r i g i n is f r o m t h e s c a p u l a a l o n g its an te r i o r b o r d e r (espec ia l l y at t he t ip ) , a n d a l o n g t h e inner o r med ia l su r f ace ad jacen t t he re to . T h e m o r e v e n t r o m e d i a l l y o r i g i n a t i n g f i be rs inser t , t o g e t h e r w i t h t he pars clavicularis, o n t he p r o x i m a l hal f o f t h e d e l t o i d r i dge of t h e h u m e r u s f r o m t h e med ia l o r an te r i o r s ide . T h e m o r e do rso la te ra l l y o r i g i n a t i n g f i be rs inser t , t o g e t h e r w i t h t h e pars epister­nalis , o n t he u lna r e p i c o n d y l e at t h e d is ta l e n d of t h e h u m e r u s . T h e pars scapularis of t h e d e l t o i d is an a b d u c t o r a n d latera l r o ta to r o f t h e a r m as we l l as a p ro t rac to r .

Veritral (Flexor) Muscles of the Shoulder Region

47. M. cu taneus pectoris ( level 2, F ig . 11). T h i s m u s c l e l ies super f i c ia l l y , benea th t he ven t ra l sk in in t he pec to ra l r e g i o n . T h e f i be rs o r i g i n a t e f r o m t h e c a r t i l a g i n o u s x i p h i s t e r n u m , a n d f r o m t h e an te r i o r m a r g i n of t he shea th w h i c h over l ies t h e rec tus a b d o m i n i s . B e t w e e n t he d i ve rg ­ing a b d o m i n a l p o r t i o n s of t he r i gh t a n d left pec to ra l i s m u s c l e s , t h e

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f i be rs of t h e m. c u t a n e u s pec to r i s r un d i rec t l y an te r io r l y , w h e r e t hey inser t in to t he d e r m i s of t h e sk in ove r l y i ng t he med ia l hal f of each c lav ic le . The an te r io r s te rna l a n d pos te r i o r s te rna l p o r t i o n s of t h e m. pec to ra l i s o r i g i na te benea th th i s musc le . T h e r igh t a n d left m m . c u t a n e u s pec to r i s are separa ted ac ross t h e ven t ra l m i d l i n e by a space of on ly m o d e r a t e w i d t h . T h e m u s c l e ac ts t o tense t h e sk in w h i c h over l ies t h e pec to ra l g i rd le .

48. M. pectoral is ( level 1 , F igs. 1 1 , 1 3 , 1 4 ) . Th i s la rge m u s c l e o c c u p i e s t h e g rea te r par t of t h e pec to ra l r e g i o n o n t h e ven t ra l s ide o f t h e body . It cons i s t s of t h ree p o r t i o n s , as f o l l o w s :

Pars sternalis anterior. T h e an te r i o r s te rna l i s p o r t i o n o r i g i na tes f r o m the o m o s t e r n u m , in c o n t a c t w i t h its pa r tne r of t h e o p p o s i t e s ide of t he body , a n d f r o m t h e ad jacen t med ia l e n d of t h e c o r a c o i d . It par t ia l ly h ides t h e pos te r i o r hal f of t h e m. co raco rad ia l i s . Its f i be rs c o n v e r g e la tera l ly , t o inser t on t h e d e l t o i d r i dge (vent ra l b o n y crest) of t h e h u m e r u s f r o m t h e med ia l o r pos te r i o r s ide , by means of a s h o r t t e n d o n w h i c h over l ies tha t of t he m. co raco rad ia l i s .

Pars sternalis posterior. T h e pos te r i o r s te rna l i s p o r t i o n o r i g i ­nates f r o m t h e m e s o s t e r n u m a n d x i p h i s t e r n u m , s o m e w h a t sepa ra ted f r o m the an te r i o r s te rna l i s p o r t i o n , bu t m o r e so f r o m t h e a b d o m i n a l i s p o r t i o n . Its f i be rs c o n v e r g e la tera l ly and inser t by means of a sho r t t e n d o n o n t o t he very base of t h e de l t o i d r idge , deep to t h e pars sternalis anterior and t he m. co raco rad ia l i s .

Pars abdominalis. T h e a b d o m i n a l p o r t i o n , la rgest of t h e t h ree , o r i g ina tes f r o m t h e a p o n e u r o s i s w h i c h cove rs t h e rec tus a b d o m i n a l i s musc le , a n d a lso f r o m the p u b i c symphys i s , by means o f f i be rs w h i c h i n t e rm ing le w i t h t h o s e of t h e m. rec tus a b d o m i n a l i s . T h e f i be rs pass an te r io r l y a n d s o m e w h a t la tera l ly as they c o n v e r g e o n t o a s t r o n g t e n d o n , w h i c h c rosses over tha t of t he m. c o r a c o r a d i a l i s t o inser t o n t he de l t o i d r i dge of t he h u m e r u s f r o m the med ia l o r pos te r i o r s ide , s o m e w h a t d is ta l t o t he i nse r t i on of t h e o the r t w o p o r t i o n s .

Al l t h ree par ts of t he m. pec to ra l i s ac t t o a d d u c t a n d re t rac t t he h u m e r u s , and a lso t o ro ta te it med ia l l y .

49. M. coracoradial is ( level 2, F igs. 1 1 , 14). Th i s ra ther s t r o n g m u s c l e o r i g ina tes f r o m t h e e p i s t e r n u m , t he o m o s t e r n u m , a n d t h e med ia l p o r t i o n s o f t h e c lav ic le a n d c o r a c o i d . Its pos te r i o r hal f is cove red by t h e an te r i o r s te rna l i s p o r t i o n of t h e m. pec to ra l i s . The f i be rs c o n v e r g e lateral ly o n t o a l o n g , s t r o n g t e n d o n , w h i c h beg ins near t h e s h o u l d e r j o in t . Th i s t e n d o n t h e n passes b e t w e e n t he a b d o m i n a l i s p o r t i o n and the o the r t w o p o r t i o n s of t h e m. pec to ra l i s , a l o n g t he de l t o i d r i dge , and be tween the t w o separa te ly i nse r t i ng ha lves of t h e pars scapularis of t he m. de l t o i deus , t o inser t j us t b e y o n d t h e e l b o w j o i n t o n t h e p r o x i m a l e n d of t h e r ad i ou lna .

50. M. coracobrachia l is longus ( level 3, F ig . 14). Th is l o n g b u t t h i n

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musc le l ies a l o n g t he c o r a c o i d , u n d e r cove r of t h e pars sternalis posterior of t h e m. pec to ra l i s . F r o m here it r uns la tera l ly , benea th al l par ts of t h e m. pec to ra l i s , t o inser t a b o u t ha l fway d o w n t h e h u m e r u s a l o n g its med ia l o r pos te r i o r s ide , deep a n d s o m e w h a t d is ta l t o t h e m. c o r a c o b r a c h i a l i s brev is i nse r t i on . Th i s m u s c l e a d d u c t s a n d re t rac ts t he a r m .

5 1 . M. coracobrachia l is brevis ( level 3, F ig . 14). Th i s m u s c l e o r i g i na tes , par t ia l ly in c o m m o n w i t h t h e p rev ious m u s c l e , f r o m t h e la tera l hal f of t he c o r a c o i d a l o n g its pos te r i o r bo rde r , a n d f r o m t h e ad jacen t par t of t he s c a p u l a near i ts pos te r i o r m a r g i n . T h e f i be rs c o n v e r g e s t r o n g l y t o w a r d t he head of t h e h u m e r u s , t o inser t mos t p r o x i m a l l y o n t he pos te r i o r o r med ia l s ide of t he h u m e r u s , i n c l u d i n g a sma l l t u b e r c l e jus t ad jacen t to t h e head , a f i ne c res t pass ing d is ta l ly t h e r e f r o m , t he p r o x i m a l p o r t i o n of t h e d e l t o i d r i dge near its base, a n d t h e space i n te rven ing be tween these . T h e m u s c l e is a re t rac to r a n d a lateral ro ta to r of t h e a r m .

Muscles of the Arrr)

52. M. tr iceps brachii ( level 1 , F igs. 10, 13, 15, 16). Th i s m u s c l e , w h i c h covers t he ex tenso r su r face of t h e h u m e r u s , o r i g i na tes in t h ree separa te p o r t i o n s o r heads . T h e / o n g head o r i g i na tes a l o n g t he pos te r i o r b o r d e r of t he scapu la , a n d a lso f r o m t h e g l e n o i d c a p s u l e ; it passes a l o n g t h e do rsa l su r f ace of t h e h u m e r u s . T h e medial head or ig ina tes a l o n g t he p r o x i m a l hal f o f t h e h u m e r u s o n its med ia l s i de ; t he lateral head o r i g i na tes a l o n g t h e p r o x i m a l hal f o f t h e h u m e r u s o n its an te r i o r o r la tera l s ide . A l l t h ree heads un i te d is ta l ly , f ina l l y g i v i n g way t o a s t r o n g t e n d o n , w h i c h passes over t he e l b o w to inser t o n t h e e x t r e m e p r o x i m a l e n d of t h e r a d i o u l n a . W i t h i n th i s t e n d o n , as it passes over t h e e l b o w , a s e s a m o i d ca r t i l age is d e v e l o p e d at t h e p o i n t of f r i c t i o n . Th i s ca r t i l age is ca l l ed t h e o lecranon, o r patella ulnaris] it s o m e t i m e s b e c o m e s f used t o ( i .e. par t of) t h e u lna . T h e t r i ceps is t h e p r i nc ipa l ex tenso r of t h e e l b o w .

53. M. anconeus ( level 3, F ig . 15). Th i s m u s c l e , a lso ca l l ed subanconeus, or ig ina tes f r o m t h e d is ta l e n d of t h e h u m e r u s a l o n g its do rsa l s ide , be tween and deep to t he va r i ous heads of t h e t r i ceps . It inser ts , in c o m m o n w i t h t he t e n d o n of t he m. t r i ceps b r a c h i i , o n t o t h e o l e c r a n o n ca r t i l age (u lnar pate l la) .

Flexor Muscles of the Forearm

54. M. f lexor carpi radial is ( level 4, F igs. 1 1 , 1 3 , 1 4 , 1 6 , 1 7 ) . Th i s m u s c l e is m o r e we l l d e v e l o p e d in males t h a n in f ema les , s i nce it is used b o t h t o f lex t he e l b o w a n d t o d r a w t h e h a n d over t o t h e rad ia l ( t h u m b ) s ide , ac t i ons used by t he ma le in t he g r a s p i n g of t h e f e m a l e d u r i n g m a t i n g .

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32 A Labo ra to r y Gu ide t o F rog A n a t o m y

The m u s c l e o r i g i na tes f r o m the d is ta l t h i r d of t h e h u m e r u s a l o n g its pos te r i o r m a r g i n ; a b o n y cres t is d e v e l o p e d in ma les on l y t o ma rk th is o r i g i n . T h e m u s c l e inser ts t e n d i n o u s l y o n t o t h e i n t e r m e d i u m .

55. M. f lexor carpi ulnaris ( level 4, F igs. 1 1 , 1 4 , 1 7 ) . Th is m u s c l e o r i g ina tes f r o m the e p i c o n d y l e o n t h e pos te r i o r (med ia l , u lnar ) s ide o f t h e d is ta l e n d of t he h u m e r u s , a n d runs a l o n g t h e f o r e a r m t o inser t b o t h o n t o t he t e n d o n of t h e p rev ious m u s c l e , a n d o n t o its o w n s h o r t t e n d o n , w h i c h a t taches o n t o t h e radía le . Th i s m u s c l e f lexes t h e h a n d a n d d raws it rad ia l ly ( t owa rd t h e t h u m b s ide) .

56. IVI. parmar is longus ( level 4, F igs. 1 1 , 14, 17). Th i s m u s c l e o r i g i na tes t o g e t h e r w i t h t h e p rev ious , f r o m t h e med ia l e p i c o n d y l e of t h e h u m e r u s . It passes a l o n g t he f l exo r su r face of t h e h a n d a n d f ina l ly b e c o m e s t e n d i n o u s . The t e n d o n sp reads o u t over t h e pa lm of t he h a n d to f o r m t h e pa lmar aponeurosis , w h i c h sends t e n d i n o u s s l ips t o each of t h e d ig i t s , a n d a lso g ives r ise t o t h e l u m b r i c a l i s m u s c l e s of t h e f i nge rs . T h e pa lmar i s l o n g u s f lexes no t on ly t h e w r i s t j o i n t , bu t a lso t he i nd i v idua l f i nge rs as w e l l .

57. M. epitrochleocubital is ( level 4, F ig . 17). Th i s m u s c l e l ies in t he m i d d l e of t he f l exo r su r face of t he f o r e a r m , bes ide t h e p rev ious musc le . It o r i g ina tes t e n d i n o u s l y f r o m t h e med ia l e p i c o n d y l e of t he h u m e r u s . Its f i be rs run d i agona l l y ac ross t h e r a d i o u l n a , t o inser t a l o n g t h e en t i re l eng th of t ha t b o n e a l o n g its u lna r m a r g i n . F ibers of t h e m. e p i c o n d y l o c u b i t a l i s inser t a l o n g th i s same l ine f r o m t h e o p p o s i t e s ide . T h e m u s c l e f lexes t h e e l b o w a n d weak l y ro ta tes it la tera l ly .

58. M. f lexor antibrachi i media i is ( level 5, F ig . 17). Th i s m u s c l e l ies o n t h e f l exo r s ide of t h e f o r e a r m , cove red by t he last t h ree m u s c l e s . T h e m u s c l e o r i g i na tes by means of a t e n d o n f r o m t h e med ia l e p i c o n d y l e of t h e h u m e r u s a n d a lso in sma l l par t f r o m t h e d e e p par t o f t h e m. f l exo r ca rp i rad ia l is . The f ibe rs inser t d i rec t l y o n t o t h e r a d i o u l n a , a l o n g its f l exo r su r face , and s o m e w h a t to t h e rad ia l s ide . T h e sho r tes t f i be rs inser t jus t d is ta l t o t h e i nse r t i on of t h e m. c o r a c o r a d i a l i s ; t h e l onges t f i be rs c o n t i n u e t o t he d is ta l e n d of t h e r ad i ou lna . T h e m u s c l e is a f l exo r of t h e e l b o w .

59. M. ulnocarpal is ( level 5, F ig . 17). Th i s deep m u s c l e ar ises u n d e r t h e cover of t h e m. pa lmar i s l o n g u s f r o m t h e d is ta l t h i r d o f t h e r a d i o u l n a a l o n g its f l exo r su r face , s o m e w h a t t o t h e u lna r s ide . It inser ts t e n d i n o u s l y o n t o t he u lna re . It f lexes t h e wr i s t .

Extensor Muscles of the Forearm

60. M. f lexor antibrachi i lateral is superf icial is ( level 4 , F ig . 17). Th i s musc le o r i g i na tes f r o m t h e la tera l (an ter io r , radia l ) e p i c o n d y l e of t he h u m e r u s a n d a lso, in c o m m o n w i t h t he m. ex tenso r ca rp i rad ia l is , f r o m the an te r i o r b o r d e r of t h e h u m e r u s ad jacen t t h e r e t o . It inser ts far

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M u s c u l a r Sys tem 33

dis ta l ly o n t h e rad ia l s ide of t h e r a d i o u l n a . It ac ts as a f l e x o r a n d latera l ro ta tor .

6 1 . M. extensor carpi radial is ( level 4, F igs. 10, 1 1 , 13, 14, 16, 17). Th i s m u s c l e l ies t o o n e s ide of t h e p rev ious , a n d o r i g i n a t e s b o t h f r o m t h e lateral e p i c o n d y l e of t h e h u m e r u s a n d f r o m t h e c res t r e a c h i n g p r o x i m a l l y t h e r e f r o m . T h e m u s c l e inser ts o n t o a t e n d o n , w h i c h b e c o m e s par t of t he j o i n t capsu le of t h e wr i s t , a t t ached b o t h t o t h e cén t ra le ( i n t e r m e d i u m ) a n d t he d is ta l e n d of t h e r a d i o u l n a . T h e m u s c l e f lexes t h e e l b o w , e x t e n d s t h e w r i s t , a n d d r a w s t h e w r i s t rad ia l ly .

62 . IVI. abductor indicis longus ( level 4, F igs. 10 ,13 ,16 ) . Th i s m u s c l e l ies o n t h e la tera l s ide of t h e f o r e a r m , w h e r e it may be seen in b e t w e e n t h e m. f l exo r a n t i b r a c h i i la tera l is supe r f i c i a l i s a n d t h e m. e x t e n s o r d i g i t o r u m c o m m u n i s l o n g u s . It o r i g i na tes in severa l p o r t i o n s , f r o m t h e la tera l e p i c o n d y l e of t h e h u m e r u s , f r o m t h e la tera l m a r g i n of t h e r a d i o u l n a , and f r o m t h e radía le. The f i be rs of al l t hese p o r t i o n s c o n v e r g e , as t hey c ross over t h e ex tenso r su r f ace of t h e f o r e a r m d iagona l l y , t o inser t o n t o t he rad ia l ( t h u m b ) s ide of t h e s e c o n d m e t a c a r p a l near i ts base. The m u s c l e a b d u c t s t h e s e c o n d f i nge r .

63. M. extensor digi torum communis longus ( level 4 , F igs. 1 0 , 1 3 , 1 6 ) . Th i s m u s c l e o r i g i na tes f r o m t h e la tera l e p i c o n d y l e of t h e h u m e r u s . Over t h e back of t h e h a n d , t he m u s c l e d i v ides in to t h ree p o r t i o n s , w h i c h en te r t h e t h i r d , f o u r t h , a n d f i f t h f i nge rs t o c o n n e c t w i t h t he m. ex tenso r brev is supe r f i c i a l i s of e a c h . T h e m u s c l e e x t e n d s t h e h a n d a n d t h e last t h ree f i nge rs .

64. M- extensor carpi ulnaris ( level 4, F igs. 10 ,16 ) . Th i s m u s c l e o r i g i na tes t o g e t h e r w i t h t he p rev i ous o n e f r o m t h e la tera l e p i c o n d y l e of t h e h u m e r u s a n d f r o m the capsu le of t h e e l b o w j o i n t . A l o n g t h e f o r e a r m , it l ies b e t w e e n t he p rev ious m u s c l e a n d t h e m. e p i c o n d y l o c u b i t a l i s . U p o n reach ing t he h a n d , it d i v ides i n to t w o p o r t i o n s , o n e i nse r t i ng o n t o t h e u lna re , t he o the r o n t o t h e f used d is ta l ca rpá is 3 -5 . It e x t e n d s t he wr i s t .

65. M. epicondylocubital is ( level 4, F ig . 17). Th i s m u s c l e ar ises by a sho r t t e n d o n f r o m the latera l e p i c o n d y l e of t h e h u m e r u s . Its f i be rs inser t d i agona l l y o n t o a l ine r u n n i n g a l o n g t he u lna r s ide o f t h e f o r e a r m ; t h e m. e p i t r o c h l e o c u b i t a l i s inser ts o n t o t h i s s a m e l ine f r o m t h e o p p o s i t e s ide. Th is m u s c l e f lexes t he e l b o w a n d ro ta tes t h e f o r e a r m med ia l l y .

66. M. f lexor antibrachi i lateral is profundus ( level 5, F ig . 17). Th i s deep m u s c l e l ies benea th t he m. e x t e n s o r ca rp i rad ia l i s a n d t h e m. f l exo r an t i b rach i i la tera l is super f i c ia l i s . It ar ises t e n d i n o u s l y f r o m t h e latera l e p i c o n d y l e of t h e h u m e r u s a n d inser ts a l o n g t he rad ia l m a r g i n of t h e rad iou lna , s o m e w h a t t o w a r d t h e f l e x o r s ide . It ro ta tes t h e f o r e a r m lateral ly .

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34 A Labo ra to r y G u i d e t o F rog A n a t o m y

Muscles of the Hand

67. M. pa lmar is profundus ( level 5, F ig . 17). Th i s m u s c l e o r i g i na tes f r o m the d is ta l e n d of t h e r a d i o u l n a a l o n g its u lna r bo rde r . F r o m here , t h e f i be rs d i ve rge as t h e m u s c l e b e c o m e s t e n d i n o u s , f u s i n g w i t h t h e deep su r face of t h e pa lma r a p o n e u r o s i s a n d i ts der i va t i ve t e n d o n s . The m u s c l e f lexes t he pa lma r a p o n e u r o s i s ( thus , t h e f i ngers ) a n d d r a w s it a lso t o w a r d t he u lna r s ide .

68. Muscles of the individual fingers (ventral or flexor side) ( level 6). The re are 27 ven t ra l o r f l exo r musc les b e l o n g i n g t o t h e i nd i v i dua l f i nge rs , i n c l u d i n g 2 fo r t h e t h u m b , 4 fo r t h e s e c o n d d ig i t , 3 fo r t he t h i r d , 6 f o r t he f o u r t h , 9 fo r t h e f i f t h , a n d 3 r u n n i n g ac ross the me taca rpa l s .

T h u m b

D ig i t II

M. abductor pollicis M. adductor pollicis M. flexor indicis superficialis

profundus M. flexor teres indicis M. lumbricalis brevis indicis M. opponens indicis M. lumbricalis brevis digiti III M. flexor teres digiti III M. flexor ossis metacarpi digiti III M. lumbricalis longus digiti IV M. interphalangealis digiti IV M. lumbricalis brevis radialis digiti IV M. lumbricalis brevis ulnaris digiti IV M. flexor teres digiti IV M. flexor ossis metacarpi digiti IV M. lumbricalis longus digiti V M. interphalangealis digiti V M. lumbricalis brevis radialis digiti V M. lumbricalis brevis ulnaris digiti V M. adductor proprius digiti V M. opponens digiti V M. abductor primus digiti V M. abductor secundus digiti V M. flexor teres digiti V M. transversus metacarpi primus M. transversus metacarpi secundus M. transversus metacarpi tertius

Dig i t III

D ig i t IV

D ig i t V

Musc les r u n n i n g ac ross t he me taca rpa l s , f r o m o n e d ig i t t o a n o t h e r

69. Muscles of the individual fingers (dorsa l o r e x t e n s o r s ide) ( level 6). T h e r e are 16 do rsa l o r ex tenso r musc les b e l o n g i n g t o t h e i nd i v i dua l

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f i nge rs , e x c e p t t he t h u m b ; these i n c l u d e 5 f o r t h e s e c o n d d ig i t , 4 e a c h fo r t he t h i r d a n d f o u r t h d ig i t s , a n d 3 fo r t h e f i f t h d ig i t .

M. extensor indicis brevis superficialis] M. extensor indicis brevis medius M. extensor indicis brevis

profundus radialis M. extensor indicis brevis

profundus ulnaris M. abductor indicis brevis dorsalis M. extensor brevis superficialis digiti III M. extensor brevis medius digiti III M. extensor brevis profundus

radialis digiti III M. extensor brevis profundus

ulnaris digiti III M. extensor brevis superficialis digiti IV M. extensor brevis medius digiti IV M. extensor brevis profundus

radialis digiti IV M. extensor brevis profundus

ulnaris digiti IV M. extensor brevis superficialis digiti V M. extensor brevis profundus

radialis digiti V M. extensor brevis profundus

ulnaris digiti V

Dig i t II

D ig i t III

D ig i t IV

D ig i t V

/. MUSCLES OF THE PELVIC GIRDLE AND HIND LIMB

Long Muscles of the Hip and Thigh

The l o n g musc les of t h e h ip a n d t h i g h are t h o s e m u s c l e s w h i c h s t re t ch f r o m t h e pe lv ic g i rd le t o t he t i b i o f i b u l a , a c t i n g ac ross b o t h t h e h ip j o i n t and t h e knee . T h e f i rs t t h ree of t hese m u s c l e s act as f l exo rs of t h e h ip a n d ex tenso rs of t h e knee . T h e r e m a i n i n g l o n g musc les of t h e h ip a n d t h i g h ac t as f l exo rs of t he knee : f ive of these a lso a d d u c t t h e t h i g h , w h i l e t h e o the r t h ree e x t e n d t h e h ip j o i n t .

T h e f o l l o w i n g t h ree m u s c l e s (Nos. 7 0 - 7 2 ) ac t t o g e t h e r t o s i m u l t a n e o u s l y f lex t h e h ip a n d e x t e n d t h e knee . S i n c e they are i n t e r c o n n e c t e d w i t h each o ther , they are o f ten desc r i bed as a s i ng le m u s c l e , t h e M. t r iceps femoris .

70. IVI. vastus internus ( level 2, F ig . 11). Th i s m u s c l e , a lso k n o w n as t h e m. c ru ra l i s , o r t he an te r i o r head of t h e t r i ceps , is t h e s t r onges t of t h e

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36 A Labo ra to r y G u i d e t o F rog A n a t o m y

th ree musc les w h i c h m a k e up t h e t r i ceps . It ar ises by means of a sho r t t e n d o n , f r o m t h e capsu le of t h e h ip j o i n t a l o n g its an te roven t ra l m a r g i n . The sho r t f i be rs o f t h i s m u s c l e s o o n g ive w a y t o a f la t t e n d o n , w h i c h covers t h e d is ta l hal f o f t h e m u s c l e supe r f i c i a l l y ; t h e r e m a i n i n g f i be rs inser t o n t o th i s t e n d o n f r o m its deep su r face , as far as t h e d is ta l p o r t i o n of t h e f emur . T h e t e n d o n j o i n s w i t h t h o s e o f t h e m. t enso r fasc iae latae a n d t h e m. vas tus ex te rnus , as it passes over t h e knee devo id of any m u s c u l a r f i be rs , t o inser t o n t o t h e an te r i o r su r f ace of t he t i b i o f i b u l a at i ts e x t r e m e p r o x i m a l e n d .

7 1 . M. tensor fasc iae la tae ( level 2, F ig . 10). Th i s m u s c l e , a lso k n o w n as t he m. rec tus f e m o r i s an t i cus , m. rec tus a n t i c u s f e m o r i s , or t he med ia l head of t h e t r i ceps , ar ises f r o m t h e an te roven t ra l r im of t h e i l i um near t h e m i d d l e of i ts l e n g t h . T h e sho r tes t a n d m o s t super f i c ia l f i be rs s o o n g ive way t o an a p o n e u r o s i s k n o w n as t h e fasc ia lata, t o w h o s e deep su r f ace t h e r e m a i n i n g f i be rs , a n d a lso t h o s e of t h e m. vas tus ex te rnus , inser t . T h e fasc ia lata cove rs t h e ven t ra l p o r t i o n of t he m. vas tus i n te rnus , w i t h w h o s e t e n d o n it f i na l l y fuses j us t be fo re pass ing over t h e knee j o i n t t o inser t h i g h u p o n t he an te r i o r su r f ace of t h e t i b i o f i b u l a .

72. M. vastus externus ( level 2, F igs. 1 0 , 1 8 ) . Th i s m u s c l e , a lso k n o w n as the m. g l u t e u s m a g n u s , o r t h e pos te r i o r head of t h e t r i ceps , ar ises by a t e n d o n f r o m t h e p o s t e r o d o r s a l c o r n e r o f t h e i l i u m , at t h e base of i ts l o n g , an te r i o r l y p r o j e c t i n g p rocess . T h e m u s c l e f o r m s a d i s t i n c t bel ly , w h o s e f ibe rs inser t , l ike t h o s e of t h e p rev ious m u s c l e , o n t o t h e deep su r face of t h e fasc ia lata.

The f o l l o w i n g f ive musc les are a d d u c t o r s of t h e t h i g h a n d f l exo rs of t h e knee :

73. M. sartorius ( level 1 , F ig . 11). T h i s l o n g , f la t m u s c l e l ies o n t h e inner o r med ia l s ide of t h e t h i g h . It ar ises by a ser ies of bare ly d i sce rn ib l e t e n d i n o u s s t rands f r o m the a n t e r o v e n t r a l m o s t c o r n e r of t h e p u b i c symphys i s . Its para l le l f i be rs run mos t super f i c ia l l y a l o n g t h e t h i g h , g i v i ng way t o a t e n d o n as they a p p r o a c h t h e knee . T h e t e n d o n runs ac ross t h e knee med ia l l y , t o inser t f r o m t h e pos te r i o r s ide o n t o t he med ia l o r i nne r su r face of t h e t i b i o f i b u l a , near i ts p r o x i m a l e n d . T h e t e n d i n o u s f ibe rs , as they sp read o u t t o f o r m t h e i nse r t i on , meet w i t h t he t e n d i n o u s i nse r t i ons o f t h e m. s e m i t e n d i n o s u s a n d t h e m. t r i ceps f emor i s .

74. M. adductor longus ( level 3, F igs , 11 ,19 ) .Th i s l o n g , f la t m u s c l e l ies u n d e r t he cove r o f t h e m. sa r to r i us . It o r i g i na tes , deep t o t h e m. sa r to r i us o r i g i n , f r o m t h e a n t e r o v e n t r a l m o s t c o r n e r of t h e p u b i c symphys i s , by means of a f la t t e n d o n . T h e m u s c l e t h e n passes over t h e med ia l o r i nner s ide of t h e t h i g h , t o inser t a l o n g t he d is ta l hal f o f t h e f e m u r o n t o t he t e n d o n of t h e m. a d d u c t o r m a g n u s .

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75. Μ- adductor magnus ( level 3, F igs. 1 1 , 1 8 , 1 9 ) . Th i s ra ther la rge m u s c l e l ies la rge ly cove red by t h e m. sa r t o r i us a n d t h e m. g rac i l i s ma jo r . It o r i g i na tes in t h ree d i s t i nc t h e a d s : t h e do rsa l a n d ven t ra l heads ar ise f r o m t h e ven t ra l o r pos te roven t ra l m a r g i n of t h e pe lv ic g i r d l e ( i s c h i u m , a lso pub is ) , separa ted f r o m each o the r by t h e ven t ra l head of t h e m. s e m i t e n d i n o s u s . T h e accesso ry head , sma l les t of t h e t h ree , ar ises f r o m t h e t e n d o n of o r i g i n of t h e ven t ra l head of t h e s e m i t e n d i n o s u s m u s c l e ; it inser ts i tsel f b e t w e e n t h e o the r t w o heads , w h e r e u p o n al l t h ree fuse , pass ing as fa r as t h e d is ta l e n d o f t h e f e m u r be fo re g i v i n g way t o t h e t e n d o n of i nse r t i on . Th i s t e n d o n , t o w h i c h t h e p rev i ous m u s c l e a lso a t taches , inser ts o n t o t h e med ia l s ide o f t h e f e m u r at i ts d is ta l e n d ; m u s c l e f i be rs of t h e m. a d d u c t o r m a g n u s a lso inser t d i rec t l y o n t o t h e d is ta l t h i r d o f t h e f e m u r , as w e l l as o n t o t h e c a p s u l e of t he knee j o i n t .

76. M. gracil is major ( level 2, F igs. 11,19) . T h i s s t r o n g m u s c l e , a lso k n o w n as the m. rec tus i n t e rnus ma jo r , l ies a l o n g t he p o s t e r o m e d i a l su r f ace of t he t h i g h . It ar ises by sho r t , t e n d i n o u s f i be rs f r o m t h e pos te r i o r m a r g i n of t h e i s c h i u m . A f te r c r o s s i n g t h e t h i g h , it g ives w a y t o a t e n d o n as it reaches t h e knee . Th i s t e n d o n t h e n b i f u r ca tes , o n e p o r t i o n i nse r t i ng f r o m the med ia l s ide o n t o t h e p r o x i m a l e n d of t h e t i b i o f i b u l a , deep t o t he m. sa r to r i us i nse r t i on , w h i l e t h e o the r p o r t i o n d ives a r o u n d t h e t e n d i n o u s inse r t i on of t h e m. s e m i t e n d i n o s u s t o inser t o n t h e pos te r i o r su r f ace of t h e t i b i o f i b u l a f r o m t h e med ia l s ide .

77. IVI. gracil is minor ( level 2, F igs. 11 ,19) . Th i s n a r r o w m u s c l e , a lso k n o w n as t h e m. rec tus i n t e rnus m i n o r , l ies bes ide t h e p rev i ous m u s c l e o n t h e p o s t e r o m e d i a l m a r g i n of t h e t h i g h . It o r i g i na tes , a l o n g w i t h its pa r tne r of t h e o p p o s i t e s ide , f r o m a m e d i a n raphe w h i c h a lso serves m o r e an te r io r l y as o r i g i n f o r f i be rs o f t h e m. rec tus a b d o m i n i s . As it c rosses t he knee , t h e m u s c l e inser ts t o t h e t e n d o n of t h e m. g rac i l i s m a j o r (q.v,).

The f o l l o w i n g th ree musc les (Nos. 78 -80) e x t e n d t h e h ip j o i n t as they f lex the knee :

78. M. i leofibularis ( level 3, F igs. 1 0 , 1 8 , 2 1 ) . T h i s m u s c l e , a lso k n o w n as t h e m. b i ceps f e m o r i s , is v i s ib le o n t h e do rsa l (pos te r io r ) s ide o f t h e t h i g h , b e t w e e n t h e m. vas tus e x t e r n u s a n d t h e m. s e m i m e m b r a n o s u s . It ar ises t e n d i n o u s l y f r o m t h e i l i u m , jus t b e h i n d t h e o r i g i n of t h e m. vas tus ex te rnus . Over t h e knee , t h e m u s c l e passes in to a t e n d o n , w h i c h t h e n f o r m s a t e n d i n o u s a r c h , i nse r t i ng m o r e p r o x i m a l l y o n t o t he med ia l su r f ace of t h e d is ta l e n d of t h e f e m u r f r o m t h e p o s t e r i o r s ide , a n d m o r e d is ta l ly , o n t o t h e la tera l o r f i bu l a r p o r t i o n of t h e t i b i o f i bu l a , near i ts p r o x i m a l e n d .

79. M. s e m i m e m b r a n o s u s ( level 2, F igs. 10, 18). Th i s s t r o n g m u s c l e beg ins w i t h a b r o a d o r i g i n a l o n g t h e p o s t e r o d o r s a l m a r g i n of t h e

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i s c h i u m . It r ema ins f leshy over t h e en t i re l eng th of t h e t h i g h , i nse r t i ng by means of a sho r t t e n d o n o n t o t h e pos te r i o r su r f ace of t h e t i b i o f i b u l a near its p r o x i m a l e n d , s u r r o u n d e d by the t e n d i n o u s a rch f r o m w h i c h t h e m. g a s t r o c n e m i u s o r i g i na tes .

80. M. semitendinosus ( level 3, F igs. 18, 19). Th i s l o n g , t h i n m u s c l e l ies ra ther do rsa l l y (pos te r io r l y ) a l o n g t h e inner o r med ia l s ide of t h e t h i g h . T h e do rsa l head ar ises by a l o n g , t h i n t e n d o n f r o m t h e pos te r i o r m a r g i n of t h e i s c h i u m , deep to t h e o r i g i n of t h e m. s e m i m e m b r a n o s u s . T h e ven t ra l head ar ises by an even n a r r o w e r t e n d o n f r o m the ven t ra l par t of t he i s c h i u m , b e t w e e n t he do rsa l a n d ven t ra l heads of t he m. a d d u c t o r m a g n u s . T h e do rsa l head of t h e m. a d d u c t o r m a g n u s l ies b e t w e e n t h e t w o heads of t h e s e m i t e n d i n o s u s ; t h e accesso ry head of tha t m u s c l e ar ises f r o m the ven t ra l head of t h e p resen t o n e . The t w o heads of t he m. s e m i t e n d i n o s u s fuse over t he m i d d l e of t he t h i g h , g i v i n g r ise t o a t e n d o n as they a p p r o a c h t h e knee . T h e t e n d o n f o r m s a t r i a n g u l a r p la te as it inser ts f r o m the pos te r i o r s ide o n t o t h e med ia l su r face of t he t i b i o f i b u l a near i ts p r o x i m a l e n d .

Short Muscles of the Hip and Thigh

T h e sho r t musc les of t h e h ip a n d t h i g h are t h o s e musc les w h i c h c ross t h e h ip j o i n t bu t do not reach t h e knee , i nse r t i ng o n t o t he f e m u r ra ther t h a n t h e t i b i o f i bu l a . At the i r o r i g i ns , these musc les l ie in t h ree layers : t h e f i rs t f o u r super f i c ia l l y , t he nex t f ou r deep t o these , and t h e m. o b t u r a t o r i n t e rnus deepest of a l l .

8 1 . M. i l iacus internus ( level 3, F ig . 18). Th i s m u s c l e ar ises f r o m t h e c o n c a v e m a r g i n of t he i l i um near its base, on t he an te r i o r s ide of t h e pe lv ic g i rd le , and a lso f r o m t h e an te r i o r m a r g i n of t h e pe lv ic g i rd le o n t he inner o r med ia l su r face of t h e i l i um at its base. It d ives b e t w e e n the m. vas tus i n te rnus a n d t he m. t enso r fasc iae latae, t o inser t bes ide the m. i l eo femora l i s o n t he latera l su r face of t he f emur . It ac ts as an a b d u c t o r of t he femur .

82. IVI. i l iacus externus ( level 4, F ig . 10, 18). Th i s musc le , a lso k n o w n as t he m. g l u teus , ar ises ra ther shee t l i ke f r o m t h e do rsa l m a r g i n of t h e i l i um a l o n g t he m i d d l e t h i r d of i ts l eng th o n t he la tera l s ide . T h e m u s c l e passes b e t w e e n t h e m. vas tus e x t e r n u s a n d t h e m. t e n s o r fasc iae latae as its f i be rs c o n v e r g e o n t o a s t r o n g t e n d o n . T h e t e n d o n inser ts ra ther h i g h o n t h e f e m u r ( to i ts t r o c h a n t e r ) , b e t w e e n t h e m. i l i acus i n t e rnus a n d m. i l eo femora l i s . It ro ta tes t h e f e m u r med ia l l y .

83. M. i leofemoral is ( level 4 , F ig . 18). Th i s sma l l m u s c l e o r i g i na tes f r o m the t e n d o n of t he m. i l eo f ibu la r i s . It inser ts o n t o t he latera l su r f ace of t he shaf t of t h e f emur , b e t w e e n t h e m. i l i acus i n te rnus a n d t he m. py r i f o rm is . It a d d u c t s a n d re t rac ts t h e f emur .

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84. Μ. pyriformis ( level 3, F igs. 10, 18). Th i s n a r r o w m u s c l e ar ises f r o m the t i p of t h e u ros ty le , and inser ts b e t w e e n t h e m. vas tus e x t e r n u s a n d m. i l eo f ibu la r i s o n one s ide , a n d t h e m. s e m i m e m b r a n o s u s o n t he o ther , o n t o t he p r o x i m a l p o r t i o n of a c res t w h i c h runs a l o n g t h e pos te rodo rsa l s ide of t h e f emur . T h e m u s c l e re t rac ts a n d a d d u c t s t he f emur .

85. M. pect ineus ( level 4, F igs. 1 1 , 19). Th i s m u s c l e o r i g i n a t e s f r o m t h e an te roven t ra l q u a d r a n t of t h e pe lv ic g i r d l e ( i n c l u d i n g t h e p u b i s a n d t he ad jacen t par t of t h e i l i um) , deep t o t h e m. sa r to r i us . F r o m here , it runs la tera l ly , t o inser t bes ide t h e m. py r i f o rm is , o n t o t h e s a m e l o n g crest , as far d is ta l l y as t h e ha l fway po i n t a l o n g t h e f e m u r . T h e m u s c l e ac ts as a p r o t r a c t o r of t h e f emur , a n d a lso (w i th t h e f e m u r p ro t rac ted ) as a f l exor .

86. M. obturator externus ( level 4, F ig . 18). Th i s m u s c l e ar ises bes ide t he m. pec t i neus , on ly m o r e pos te r i o r l y . It para l le ls t h e la t ter m u s c l e t h r o u g h o u t its l e n g t h , to inser t bes ide it med ia l l y a l o n g t h e pos te r i o r s ide of t he f emur . Th i s m u s c l e f l exes t h e f e m u r . Th i s m u s c l e is s o m e t i m e s d e s c r i b e d t o g e t h e r w i t h t he nex t t w o , u n d e r t h e n a m e m. a d d u c t o r brev is .

87. M. quadratus femor is ( level 4, F ig . 18). Ar ises f r o m t h e pos te r i o r p o r t i o n of t h e pe lv ic g i r d l e u n d e r cove r of t h e do rsa l head of t h e m. a d d u c t o r m a g n u s . T h e f ibe rs c o n v e r g e t o a res t r i c ted area of i nse r t i on on t h e f emur , p r o x i m a l a n d do rsa l t o tha t of t h e m. o b t u r a t o r e x t e r n u s . A d d u c t s t he f emur .

88. IVI. gemel lus ( level 4, F ig . 18). Th i s m u s c l e ar ises m o s t do rsa l l y f r o m the i s c h i u m , u n d e r cove r of t h e m. s e m i m e m b r a n o s u s . Its f i be rs c o n v e r g e t o an i nse r t i on p r o x i m a l t o t ha t of t h e p rev i ous m u s c l e . It a d d u c t s a n d re t rac ts t h e f emur .

89. M. obturator internus ( level 5, F ig . 18). Th i s m u s c l e is t h e deepes t of al l musc les of t h e h ip . It s u r r o u n d s t he a c e t a b u l u m f r o m t h r e e s ides , o r i g i n a t i n g an te r io r , ven t ra l , a n d pos te r i o r t he re to . F r o m here , t he f ibers c o n v e r g e in sp i ra l f a s h i o n o n t o a t e n d o n , by w h i c h t h e m u s c l e inser ts h i g h on the p o s t e r o d o r s a l m a r g i n of t h e f e m u r , near i ts head . T h e m u s c l e a d d u c t s t he f e m u r a n d ro ta tes it la tera l ly .

Muscles of the Lower Leg

The f i rs t t w o of these musc les are ex tenso rs of t he a n k l e ; t he r e m a i n i n g f o u r are f l exo rs of th i s j o i n t . Severa l of t hese musc les act ac ross t h e knee j o i n t as w e l l , usua l ly p e r f o r m i n g t h e o p p o s i t e m o t i o n here as ac ross t h e ank le .

90. M. gast rocnemius ( level 1 , F igs. 10, 1 1 , 21). Th i s m u s c l e , a lso k n o w n as t h e m. p lan ta r i s l o n g u s , is by far t h e s t r o n g e s t m u s c l e of t h e h i n d l imb , and is t he p r i nc i pa l m u s c l e used by t h e f r o g in j u m p i n g . T h e

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m u s c l e ar ises f r o m a t e n d i n o u s a r c h , w h i c h c o n n e c t s t h e ad j acen t ends of t h e f e m u r a n d t i b i o f i b u l a ac ross t h e knee j o i n t . A sma l l n u m b e r of f i be rs a lso ar ise t e n d i n o u s l y f r o m t h e la tera l m a r g i n of t h e fasc ia lata (see No. 7 1 , above) as it c rosses t h e knee capsu le . T h e m u s c l e t h e n deve lops a very s t r o n g , meaty bel ly ( f r ogs ' l egs—the g o u r m e t ' s de l i gh t ! ) , o n w h o s e l owe r hal f a supe r f i c i a l a p o n e u r o s i s appears . Th i s a p o n e u r o s i s g ives r ise t o a l o n g , s t r o n g t e n d o n , t he tendon of Achi l les, w h i c h c rosses t h e " h e e l " o f t h e a n k l e j o i n t a n d t h e n sp reads o u t a l o n g t he " s o l e " of t h e f o o t t o f o r m a plantar aponeurosis , w h i c h in t u r n g ives r ise t o o t h e r m u s c l e s a n d a lso sends t e n d i n o u s s t rands in to each of t h e severa l d ig i t s . T h e g a s t r o c n e m i u s m u s c l e is t h e p r i n c i p a l e x t e n s o r m u s c l e o f t h e a n k l e j o i n t . (For advanced s t u d e n t s : Th i s m o v e m e n t of t h e ank le , t h o u g h desc r ip t i ve ly an e x t e n s i o n , c o r r e s p o n d s m o r e c lose ly t o t h e ac t of flexion in t h e wr i s t . For t h i s reason , w e may u n a m b i g u o u s l y d e s i g n a t e t h i s m o t i o n as p lantar f lexion, and t h e c o r r e s p o n d i n g o p p o s i t e m o t i o n as dorsi -f lexion.)

9 1 . M. tibialis posterior ( level 3, F igs. 1 1 , 21). Th i s t h i n m u s c l e l ies benea th t h e m. g a s t r o c n e m i u s a n d t o w a r d t h e inner (med ia l ) o r t i b ia l s ide a l o n g t he pos te r i o r su r f ace of t h e t i b i o f i b u l a . Its f i be rs t ake o r i g i n al l a l o n g th i s b o n e as far as its d is ta l e n d , r u n n i n g d i agona l l y t o c o n v e r g e u p o n a t e n d o n w h i c h spans t h e ank le j o i n t t o inser t o n t he p r o x i m a l e n d of t h e t i b ia le . The m u s c l e is a p lan ta r f l exo r , a n d a lso an a d d u c t o r (p rona to r ) of t h e f oo t .

92. M. peroneus ( level 2, F igs. 1 0 , 2 0 , 2 1 ) . Th i s l o n g bu t s t r o n g m u s c l e l ies a l o n g t h e ou te r ( lateral) s ide of t h e leg , b e t w e e n t h e m. g a s t r o c n e m i u s and t h e m. t i b ia l i s a n t i c u s l o n g u s . It ar ises q u i t e far la tera l ly a l o n g t he ex tenso r su r face of t he knee by means of a s t r o n g bu t n a r r o w t e n d o n . T h e m u s c l e inser ts by m e a n s of t w o t e n d o n s , w h i c h t o g e t h e r f o r m a t e n d i n o u s a r c h . O n e e n d of t h i s a r ch is a n c h o r e d t o t h e d is ta l e n d of t h e t i b i o f i b u l a , t h e o the r t o t h e la tera l c o r n e r o f t h e f i bu l a re . T h e t e n d o n of o r i g i n of t h e m. ta rsa l is an te r i o r (see be l ow . No. 103) passes unde r t h i s t e n d i n o u s a r c h . T h e m. p e r o n e u s e x t e n d s t h e knee , do rs i f l exes t he f oo t , and p rona tes it.

93. M. tibialis ant icus longus ( level 2, F igs. 10, 1 1 , 20). Th i s m u s c l e ar ises by means of a t h i n , l ong t e n d o n w h i c h c rosses o b l i q u e l y over t h e ex tenso r s ide o f t h e knee f r o m t h e d is ta l e n d o f t h e f e m u r . T h e m u s c l e f ibe rs o r i g i na te t o e i the r s ide of t h i s t e n d o n , f o r m i n g t w o be l l ies over t h e an te r i o r s ide o f t h e l owe r l eg . Each of t hese t w o be l l ies e n d s in a l o n g , n a r r o w t e n d o n , t he m o r e med ia l of t h e t w o c r o s s i n g over t h e t e n d o n of t h e m. t i b ia l i s pos te r i o r t o inser t nea rby o n t h e t i b ia le , t h e o the r t e n d o n d i ve rg i ng lateral ly t o inser t o n t he f i bu la re . The m u s c l e ac ts in t h e e x t e n s i o n of t h e knee a n d t h e do rsa l f l e x i o n of t h e ank le .

94. M. extensor cruris ( level 3, F igs. 1 1 , 20). Th i s m u s c l e , a lso k n o w n as

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t h e m. ex tenso r c ru r i s brev is , l ies o n t h e la tera l s ide of t h e l owe r leg , ad jacen t t o t he m. t i b ia l i s a n t i c u s l o n g u s . Its s o m e w h a t l o n g a n d t h i n t e n d o n of o r i g i n ar ises f r o m t h e med ia l s ide of t h e d is ta l e n d of t h e f emur , a n d c rosses t h e knee jus t para l le l med ia l l y t o t h e t e n d o n of t h e m. t i b ia l i s a n t i c u s l o n g u s . T h e m u s c l e inser ts d i rec t l y o n t o t h e la tera l m a r g i n of t h e t i b i o f i b u l a , near i ts d is ta l e n d . It e x t e n d s t h e knee .

95. M. t ibialis ant icus brevis ( level 3, F ig . 20). Th i s m u s c l e ar ises f r o m t h e an te r i o r su r f ace of t he t i b i o f i b u l a over i ts m i d d l e t h i r d , b e t w e e n t h e m. t i b ia l i s a n t i c u s l o n g u s a n d t h e m. e x t e n s o r c ru r i s b rev is . T h e m u s c l e d r i f t s g radua l l y med ia l l y as it passes d is ta l ly , pa ra l l e l i ng t he med ia l p o r t i o n of t h e m. t i b ia l i s a n t i c u s l o n g u s . T h e m u s c l e t h e n g ives w a y t o a t h i n t e n d o n , w h i c h is c rossed over by tha t of t h e med ia l p o r t i o n o f t he m. t i b ia l i s a n t i c u s l o n g u s . It t h e n inser ts t o t h e p r o x i m a l e n d of t h e t ib ia le , near t he i nse r t i on of t h e m. t i b ia l i s a n t i c u s l o n g u s , a n d jus t med ia l t o t he i nse r t i on of t h e m. t i b ia l i s pos te r io r . T h e m u s c l e f lexes t he f o o t dorsa l l y , a n d t u r n s t h e so le i nward l y .

Muscles of the Foot

T h e musc les of t he f o o t are a r r a n g e d in t w o g r o u p s : t h e m u s c l e s o n t h e so le of t he f o o t ( f lexor musc les ) , a n d t h e m u s c l e s of t h e d o r s u m of t h e f o o t (ex tensor musc les ) . T h e f l exo r musc les w i l l be l is ted f i rs t (Nos. 9 6 - 1 0 2 ) ; t he ex tenso r musc les w i l l be t rea ted last (Nos. 103-104) .

96. Μ- tarsal is posterior ( level 5, F igs. 20, 21). Th i s m u s c l e ar ises f r o m a s t r o n g l i gamen t ( the l igamentum calcanei ) w h i c h runs f r o m s ide t o s ide ac ross t h e p lan ta r su r f ace of t h e t a r sus at its e x t r e m e p r o x i m a l e n d . Th i s l i gamen t a lso c o n t a i n s a s e s a m o i d ca r t i l age t o w a r d its med ia l s i de ; f i be rs of t h e m. ta rsa l i s p o s t e r i o r o r i g i n a t e f r o m th i s ca r t i l age as w e l l . T h e m u s c l e inser ts o n t o t h e p lan ta r s u r f a c e of t h e t ib ia le over t he d is ta l t w o - t h i r d s o f i ts l e n g t h . T h e m u s c l e ac ts in t h e p lan ta r f l e x i o n of t h e f oo t , a n d in t u r n i n g t h e so le of t h e f o o t o u t w a r d .

97. M. plantaris profundus ( level 5, F ig . 21). Th i s m u s c l e o r i g i n a t e s f r o m the l i g a m e n t u m ca lcane i a n d its s e s a m o i d ca r t i l age , par t ia l l y ove r l y i ng t he p rev ious m u s c l e . It sp reads o u t over t h e so le , t o inser t o n t o t h e deep (dorsa l ) su r face of t h e p lan ta r a p o n e u r o s i s . It t enses t h e p a l m a r a p o n e u r o s i s a n d t h u s ind i rec t l y f l exes t h e f i rs t t h ree d ig i t s of t h e f oo t .

98. M. f lexor digitorum brevis superf icial is ( level 5, F ig . 21). Th i s m u s c l e o r i g i na tes mos t la tera l ly f r o m t h e l i g a m e n t u m ca l cane i . A t t h e level of t he ta rsometa ta rsa l j o i n t , t he m u s c l e g ives r ise ra ther a b r u p t l y t o a t e n d o n w h i c h t h e n t r i f u r ca tes , s e n d i n g t e n d i n o u s s l ips t o each of d ig i t s III, IV, a n d V. The m u s c l e f lexes t h o s e d ig i t s t o w h i c h it inser ts .

99. M. t ransversus p lantae proximal is ( level 5, F ig . 26). Th i s m u s c l e ar ises f r o m t h e d is ta l e n d of t h e f i bu l a re , c r o s s i n g t h e so le of t h e f o o t

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42 A Labo ra to r y t o F rog A n a t o m y

t ransverse ly as a b r o a d , f lat sheet . Its f i be rs p r o c e e d med ia l l y , t o inser t o n t o t h e p lan ta r a p o n e u r o s i s f r o m the deep o r do rsa l s ide . T h e m u s c l e d r a w s t h e med ia l p o r t i o n of t h i s a p o n e u r o s i s la tera l ly , ass is t ing t h e l umbr i ca l es of t h e f i rs t t h ree d ig i t s espec ia l l y .

100. M. t ransversus p lantae distal is ( level 5, F ig . 26). T h i s m u s c l e ar ises f r o m a s e s a m o i d ca r t i l age tha t l ies w i t h i n t h e so le o f t h e f o o t . Its f i be rs run med ia l l y and s o m e w h a t d is ta l ly , s o m e of t h e m i nse r t i ng o n t o t h e p lan ta r a p o n e u r o s i s , a n d o the rs o n t o a t e n d o n , a t t ached t o t h e p lan ta r a p o n e u r o s i s , f r o m w h i c h t he m. l umb r i ca l i s l o n g u s d ig i t i III and m. l umb r i ca l i s brev is d ig i t i IV o r i g i na te . The m u s c l e ass is ts in t he f i xa t i on of these lat ter at t he i r o r i g i n .

1 0 1 . M. intertarsal is ( level 5, F ig . 26). Th i s s t r o n g m u s c l e is t h e deepes t of t he musc les of t h e so le . It ar ises over t h e p r o x i m a l t w o - t h i r d s of t h e f i bu la re , a n d t o a lesser ex ten t f r o m the p r o x i m a l t h i r d of t he t i b ia le . T h e f ibe rs of t h i s m u s c l e c o n v e r g e o n t o a s t r o n g t e n d o n , w h i c h inser ts o n t o t he p lan ta r su r face of t h e cén t ra le . T h e m u s c l e a d d u c t s t h e f o o t a n d t u r n s t he so le o u t w a r d .

102. Muscles of the individual toes (plantar or flexor surface) ( level 6). The re are 32 p lan ta r o r f l exo r musc les b e l o n g i n g t o t h e i nd i v i dua l t oes of t h e foo t . These i n c l u d e 1 fo r t h e p reha l l ux , 4 fo r t h e ha l l ux (b ig toe) , 3 f o r t h e s e c o n d toe , 5 f o r t h e t h i r d , 9 f o r t he f o u r t h , 6 f o r t h e f i f t h , a n d 4 r u n n i n g ac ross t he meta ta rsa ls .

M. abductor prehallucis} P reha l l ux M. lumbricalis brevis hallucis M. flexor teres hallucis M. abductor brevis plantaris hallucis M. opponens hallucis M. lumbricalis brevis digiti II M. flexor teres digiti II M. flexor ossis metatarsi digiti M. lumbricalis longus digiti III M. interphalangeus digiti III M. lumbricalis brevis digiti III M. flexor teres digiti III M. flexor ossis metatarsi digiti III M. lumbricalis longissimus digiti IV M. interphalangeus distalis digiti IV M. lumbricalis longus digiti IV M. interphalangeus proximalis digiti IV M. lumbricalis brevis lateralis digiti IV M. lumbricalis brevis mediaiis digiti IV M. flexor teres digiti IV M. flexor ossis metatarsi digiti IV M. abductor proprius digiti IV

Hal lux (D ig i t I)

D ig i t II

D ig i t III

D ig i t IV

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M u s c u l a r Sys tem 43

Μ. lumbricalis longus digiti V M. interphalangeus digiti V M, lumbricalis brevis lateralis digiti V M. lumbricalis brevis medialis digiti V M. flexor teres digiti V M. abductor brevis plantaris digiti V M. transversus metatarsi primus M. transversus metatarsi secundus M. transversus metatarsi tertius M. transversus metatarsi quartus

Dig i t V

M u s c l e s r u n n i n g ac ross t h e meta ta rsa ls , f r o m o n e d i g i t t o a n o t h e r

T h e r e m a i n i n g musc les of t h e f o o t (Nos. 103-104) l ie o n i ts do rsa l su r f ace and are p r imar i l y ex tenso rs .

103. M. tarsal is anterior ( level 5, F igs . 1 1 , 20). Th i s fa i r ly s t r o n g m u s c l e ar ises by a br ie f t e n d o n f r o m t h e pos te ro la te ra l m a r g i n of t h e t i b i o f i b u l a at i ts d is ta l e n d , u n d e r cove r of t h e m. t i b ia l i s a n t i c u s l o n g u s . F r o m here , it r uns o n t o t h e do rsa l su r f ace of t h e f oo t , w h e r e it inser ts o n t o t h e t ib ia le , a l o n g its m o r e d i s t a l hal f . T h e m u s c l e i s a d o r s i f l e x o r of t h e f o o t ; it a lso sup ina tes t he f oo t , so tha t t h e so le faces i nward l y .

104. Muscles of the individual toes (dorsal or extensor surface) ( level 6). The re are 22 do rsa l o r e x t e n s o r m u s c l e s of t h e i nd i v i dua l t oes , i n c l u d i n g 5 f o r t h e ha l l ux (b ig toe) , 4 f o r t h e s e c o n d d ig i t , 4 f o r t h e t h i r d , 5 fo r t h e f o u r t h , a n d 4 fo r t h e f i f t h .

M. extensor brevis superficialis hallucis M. extensor brevis medius hallucis M. extensor brevis profundus

lateralis hallucis M. extensor brevis profundus

medialis hallucis M. abductor brevis dorsalis hallucis M. extensor brevis superficialis digiti II M. extensor brevis medius digiti II M. extensor brevis profundus

lateralis digiti II M. extensor brevis profundus

medialis digiti II M. extensor brevis superficialis digiti III M. extensor brevis medius digiti III M. extensor brevis profundus

lateralis digiti III M. extensor brevis profundus

medialis digiti III

Hal lux (D ig i t I)

D ig i t II

D ig i t III

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44 A Labo ra to r y G u i d e t o F rog A n a t o m y

M. extensor longus digiti IV M. extensor brevis medius

lateralis digiti IV M. extensor brevis medius

medians digiti IV \ D ig i t IV M. extensor brevis profundus

lateralis digiti IV M. extensor brevis profundus

medians digiti IV M. extensor brevis superficialis digiti V M. extensor brevis profundus

lateralis digiti V M. extensor brevis profundus

medians digiti V M. abductor brevis dorsalis digiti V I

Dig i t V

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7. Μ. RHOMBOIDEUS ANTERIOR

29. Μ. DEPRESSOR MANDIBULAE

45. Μ. DORSALIS SCAPULAE

25. M. TEMPORALIS

9. M. LEVATOR SCAPULAE SUPERIOR

10. M. LEVATOR SCAPULAE INFERIOR

42. M. CUCULLARIS

61. M. EXTENSOR CARPI RADIALIS

62. M. ABDUCTOR INDICIS LONGUS

63. M. EXTENSOR DIGITORUM COMMUNIS LONGUS

64. M. EXTENSOR CARPI ULNARIS

14. M. CUTANEUS ABDOMINIS

78. M. ILEOFIBULARIS

AREA OF ORIGIN OF M. DORSALIS SCAPULAE (stippled)

13. M. SERRATUS INFERIOR

12. M. SERRATUS MEDIUS

5. M. INTERTRANSVERSARIUS

18. M. SPHINCTER ANI

72. M. VASTUS EXTERNUS

92. M. PERONEUS

93. M. TIBIALIS ANTICUS LONGUS

Fig. 10 Superficial muscles, dorsal view. Certain superficial muscles and other overlying structures have been removed on the right side, in order to

reveal a slightly deeper layer. 45

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30. Μ. MYLOHYOIDEUS

31 . Μ. SUBHYOIDEUS

56. Μ. PALMARIS LONGUS

55. Μ. FLEXOR CARPI ULNARIS

17. M. OBLIQUUS INTERNUS

16. M. OBLIQUUS EXTERNUS

48. M. PECTORALIS

94. M. EXTENSOR CRURIS

93. M. TIBIALIS ANTICUS LONGUS

46. M. DELTOID

49. M. CORACOl

75. M. ADDUCTOR MAGNUS

103. M. TARSALIS ANTERIOR

Fig. 11 Superficial muscles, ventral view.

46

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32. Μ. SUBMENTALIS

33. Μ. QENIOGLOSSUS

30. Μ. MYLOHYOIDEUS (major portion cut away to reveal underlying muscles)

31. M. SUBHYOIDEUS (cut)

34. M. HYOGLOSSUS

35. M. GENIOHYOIDEUS

INSERTION OF MM. STERNOHYOIDEUS AND OMOHYOIDEUS

38. M. PETROHYOIDEUS ANTERIOR

3 9 - 4 1 . MM. PETROHYOIDEI POSTERIORES I, II. AND III

15. M. RECTUS ABDOMINIS 36. M. STERNOHYOIDEUS (cut on left side) -

Fig. 12 Muscles of the head region, ventral view. The left side (i.e. the right half of the diagram) represents a somewhat deeper dissection.

44. M. LATISSIMUS DORSI 45. M. DORSALIS SCAPULAE 25. M. TEMPORALIS

17. M. OBLIQUUS INTERNUS

52. M. TRICEPS BRACHII

54. M. FLEXOR CARPI RADIALIS

61 . M. EXTENSOR CARPI RADIALIS

- 6 2 . M. ABDUCTOR INDICIS LONGUS

' 6 3 . M. EXTENSOR DIGITORUM COMMUNIS LONGUS

Fig. 13 Superficial muscles of the head and shoulder regions, lateral view.

47

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48 A Labo ra to r y G u i d e t o F rog A n a t o m y

46. M. DELTOIDEUS

56. M. PALMARIS LONGUS

55. M. FLEXOR CARPI ULNARIS

54. M. FLEXOR CARPI RADIALIS

TENDON OF M. CORACORADIALIS

51. M. CORACOBRACHIALIS BREVIS

50. M. CORACOBRACHIALIS LONGUS

Fig. 14 Pectoral region, deep dissection (ventral view).

7. M. RHOMBOIDEUS A N T E R P

8. M. RHOMBOIDEUS POSTERIOR

28. M. PTERYGOIDEUS 24. M. RECTUS LATERALIS

19. M. RECTUS SUPERIOR

23. M. OBLIQUUS SUPERIOR

22. M. OBLIQUUS INFERIOR

52. M. TRICEPS BRACHII

45. M. DORSALIS SCAPULAE

•44. M. LATISSIMUS DORSI

Fig. 15 Head and shoulder regions, deep dissection (lateral view).

49. M. CORACORADIALIS

61. M. EXTENSOR CARPI RADIALIS

48. M. PECTORALIS (insertions)

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M u s c u l a r Sys tem 49

62. Μ. A B D U a O R INDICIS LONGUS

54. M. FLEXOR CARPI RADIALIS.

TENDON OF M. BRACHIORADIALIS

63. M. EXTENSOR DIGITORUM COMMUNIS LONGUS

.64. M. EXTENSOR CARPI ULNARIS

52. M. TRICEPS BRACHII

Fig. 16 Muscles of the forearm and hand, dorsal view.

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50 A Labo ra to r y G u i d e t o F rog A n a t o m y

67. M. PALMARIS PROFUNDUS

65. M. EPICONDYLOCUBITALIS

57. M. EPITROCHLEOCUBITALIS

56. M. PALMARIS LONGUS

55. M. FLEXOR CARPI ULNARIS

LUMBRICALIS MUSCLES

PALMAR APONEUROSIS

59. M. ULNOCARPALIS

58. M. FLEXOR ANTIBRACHII MEDIALIS

M. FLEXOR ANTIBRACHII LATERALIS PROFUNDUS

61. M. EXTENSOR CARPI RADIALIS

60. M. FLEXOR ANTIBRACHII LATERALIS SUPERFICIALIS

TENDON OF M. BRACHIORADIALIS

54. M. FLEXOR CARPI RADIALIS

Fig. 17 Muscles of the forearm and hand, ventral view.

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M u s c u l a r Sys tem 51

UROSTYLE ILIUM

6. M. COCCYGEOILIACUS

82. M, ILIACUS EXTERNUS

. S E M I M E M B R A N O S U S (cut) \ \ VENTRAL HEAD Λ 86. Μ. OBTURATOR EXTERNUS V I ^ ^ A C C E S S O R Y V " ™ λ

80. Μ. S E M I T E N D I N O S U S - - ^ ^ ^ ^ HEAD DORSAL HEAD \ 75. M. ADDUCTOR MAGNUS

Fig. 18 Deep muscles of the pelvic region, dorsal view.

' 74. M. ADDUCTOR LONGUS

75. M. ADDUCTOR MAGNUS

77. M. GRACILIS MINOR (cut)

76. M. GRACILIS MAJOR (cut)

TIBIOFIBULA

Fig. 19 Deep muscles of the pelvic region, ventral view.

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52 A Labo ra to r y G u i d e t o F rog A n a t o m y

92. M. PERONEUS -

94. M. EXTENSOR CRURIS

93. M. TIBIALIS ANTICUS L O N G U S ,

104. M. ABDUCTOR BREVIS DORSALIS DIGITI V

104. MM. EXTENSORES BREVES^

95. M. TIBIALIS ANTICUS BREVIS

104. M. EXTENSOR LONGUS DIGITI IV

103. M. TARSALIS ANTERIOR

96. M. TARSALIS POSTERIOR

PREHALLUX

Fig. 20 Muscles of the leg and foot, anterior view.

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M u s c u l a r Sys tem 53

FEMUR

78. M. ILEOFIBULARIS

TENDON OF MM. GRACILIS MAJOR AND

91. M. TIBIALIS POSTERIOR

TIBIOFIBULA

92. M. PERONEUS

96. M. TARSALIS POSTERIOR

97. M. PLANTARIS PROFUNDUS

PREHALLUX

LUMBRICALIS MUSCLES

90. M. GASTROCNEMIUS

98. M. FLEXOR DIGITORUM BREVIS SUPERFICIALIS

PLANTAR APONEUROSIS (reflected)

ACHILLES TENDON

Fig. 21 Muscles of the leg and foot, posterior view.

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54 A Labo ra to r y G u i d e t o F rog A n a t o m y

.SKULL

4. MM. INTERCRURALES

5. MM. INTERTRANSVERSARII

Fig, 22 Mm. intercrurales and intertransversarii, dorsal view.

42. M. CUCULLARIS

39 -41 . MM, PETROHYOIDEI « t . . . 31 . Μ. SUBHYOIDEUS

• I II

III

POSTERIORES 30. M. MYLOHYOIDEUS

HYOID CARTILAGE

38. M. PETROHYOIDEUS ANTERIOR

Fig. 23 The petrohyoideus and subhyoideus muscles, and associated structures; obl ique ventrolateral view.

78. M. ILEOFIBULARIS and 83. M. ILEOFEMORALIS

18. M. OBLIQUUS EXTERNUS

89. M. OBTURATOR INTERNUS

79. M. SEMIMEMBRANOSUS 86. M. GEMELLUS

80. M. SEMITENDINOSUS 87. M. QUADRATUS FEMORIS,

76. M. GRACILIS MAJOR

75. M. ADDUCTOR MAGNUS" 80. M. SEMITENDINOSUS ^

17. M.^OBLIQUUS INTERNUS

' 71 . M. TENSOR FASCIAE LATAE

- 81 . M. ILIACUS INTERNUS

74. M. ADDUCTOR LONGUS

- 73. M. SARTORIUS

> 0 . . M . VASTUS INTERNUS 86. M. OBTURATOR EXTERNUS 85. M. PECTINEUS

Fig. 24 Lateral view of the pelvic girdle, showing areas of muscle attach­ment.

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M u s c u l a r Sys tem 55

7. Μ. RHOMBOIDEUS ANTERIOR

9. M. LEVATOR SCAPULAE SUPERIOR

8. M. RHOMBOIDEUS POSTERIOR

11. M. SERRATUS SUPERIOR

43. M. INTERSCAPUURIS

42. M. CUCULLARIS

12. M. SERRATUS MEDIUS

10. M. LEVATOR SCAPULAE INFERIOR

13. M. SERRATUS INFERIOR

37. M. OMOHYOIDEUS

Fig. 25 Internal (medial) view of the right scapula and suprascapula, showing areas of muscle attachment.

TIBÍALE (ASTRAGALUS)

LUMBRICALIS MUSCLES

FIBULARE (CALCANEUM)

101. M. INTERTARSALIS

99. M. TRANSVERSUS PLANTAE PROXIMALIS

100. M. TRANSVERSUS PLANTAE DISTALIS

INTERPHALANGEUS MUSCLES

Fig. 26 Deeper muscles on the plantar surface of the tarsus and foot.

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56 A Labo ra to r y Gu ide t o F rog A n a t o m y

J. A CLASSIFICATION OF THE MUSCLES ( for a d v a n c e d s t u d e n t s on ly )

T h e f o l l o w i n g c lass i f i ca t i on , p resen ted here f o r t h e bene f i t of t h e m o r e a d v a n c e d s tuden t s , is based u p o n t h e i nne rva t i on of t h e v a r i o u s musc les , o n the i r e m b r y o l o g i c a l o r i g i n , a n d o n va r i ous p h y l o g e n e t i c p r i nc i p l es a n d fac ts w h o s e d i s c u s s i o n does no t seem a p p r o p r i a t e here . Many of t h e d i f f e rences b e t w e e n i m p o r t a n t m u s c l e g r o u p s are s ta ted w i t h an i n t e n t i o n a l brev i ty , leav ing the i r m o r e c o m p l e t e e x p l a n a t i o n t o t h e i ns t ruc to r .

VISCERAL (BRANCHIOMERIC) MUSCLES—derived embryological ly f rom neural crest, and phylogenetically f rom gil l muscles.

Mandibular arch musculature (tr igeminal nerve field) Nos. 25-28, 30, 32 Hyoid arch musculature (facial nerve field) Nos. 29, 31 First branchial arch musculature (glossopharyngeal nerve field) No. 38 Posterior branchial arch musculature (vagus and accessory nerve fields)

Nos. 39-43 SOMATIC MUSCLES—derived from somites

AXIAL MUSCLES—derived directly f rom somites; primitively associated wi th axial skeleton.

Derivatives of the prebranchial somites (extrinsic ocular musculature) Nos. 19-24

Derivatives of the postbranchial somites Epaxial musculature (field of dorsal rami) Nos. 1-5 Hypaxial musculature (field of ventral rami)

Craniocervical division Hypoglossal musculature Nos. 33-37 Dorsoscapular musculature Nos. 7-13

Thoraco-abdominal division Nos. 14-17 Sacrocaudal division Nos. 6, 18

APPENDICULAR MUSCLES—derived from l imb bud mesenchyme of somatic or ig in; primitively associated wi th l imbs.

FORELIMB Dorsal or extensor division

Shoulder extensor group Nos. 44-46 Brachial extensor group Nos. 52-53 Antebrachial extensor group (n. radialis) Nos. 60-66 Manual extensor group (n. radialis) Nos. 67-68

Ventral or f lexor division Pectoral group Nos. 47-51 Antebrachial f lexor group (n. ulnaris) Nos. 54-59 Manual f lexor group (n. ulnaris) No. 69

HIND LIMB Proximal musculature (hip and thigh)

Field of n. ischiadicus Nos. 70, 72-73, 75-80, 83-84, 86-89 Field of n. cruralis Nos. 71 , 74, 81-82, 85

Distal musculature (lower leg and foot) Field of n. t ibial is—flexor muscles Nos. 90 -91 , 96-102 Field of n. peroneus—extensor muscles Nos. 92-95,103-104


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Muscular System- Comaparative Anatomy

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Anatomy skeletal muscular

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Anatomy of Frog - Union-Endicott Central School District

Anatomy of Frog - Union-Endicott Central School District

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Lab Anatomy of Muscular System

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Frog Anatomy Lab - Corrie Martin - Homecmartinresgmsd.weebly.com/uploads/3/8/3/1/38314033/frog_dissection...Frog Anatomy Lab Adapted from Ms. Polson November 15, 2009 Frog Facts !

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Frog Anatomy and morphology

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Bio 11 3rd Lab Frog Anatomy

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Frog anatomy

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Basic Frog Anatomy

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The Frog DIGESTIVE, MUSCULAR & CIRCULATORY STRUCTURES

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