PRINICIPLES OF MYOLOGY Def: science deals with muscles Dr: Ahmed SaberVet. Anat. 1. 2008 Skeletal muscles are the active part of locomotor system Smooth

PRINICIPLES OF MYOLOGY

Def: science deals with muscles

Dr: Ahmed Saber Vet. Anat. 1. 2008

Skeletal muscles are the active part of locomotor systemSmooth muscles move the visceraCardiac muscle produces heart contraction

The main characters of muscles are: Irritability or Excitability - responsive to chemical, electrical, or mechanical stimuliContractility - ability of muscle to contract (shorten)Extensibility - ability to be passively stretched Elasticity - ability to return to its original length


Types of muscles

1- smooth muscles:• Structures: long spindle

shaped, uni-nucleate, and non-striated (smooth)

• Locations: wall of visceral organ

• The control: involuntary autonomic control or endocrine control (myo-epithelial cells)

• function: Involuntary contractions that move materials through the organs


2- Cardiac muscles• Structures:

cylindrical, mostly uninucleate striated, and Branching and joins forming myocardium network (syncytium).The fibers are connected end-to-end at sites called intercalated disks.


• Locations: wall of heart• The control: involuntary• function: Involuntary autonomic

control and special local conducting system cause contractions of heart


3- Skeletal musclesThey forming about 40-45 % of

body weightThe muscle cell = muscle fiber

= myofiber• structures:

– Elongated, multinucleated, with long and transverse striation.

– Each muscle is divided into bundles or fascicles

– Each fascicles is composed of numerous muscle fiber (cells)

• Locations: in all body & forming active part of locomotor system


Skeletal muscles (cont.)• The control: voluntary controlfunction: • voluntary somatic movement of the body• Maintain body position• Stabilizing the joint• Heat production• Guarded body entrances and orifices


Architecture of skeletal muscle

• Each single muscle is consists of numerous bundles (fascicles)

• Each fascicles is consists of numerous muscle fibers

• The muscle fiber is the structural unite of muscle

boneTendon

MuscleEpimysium

Fascicle Fiber


Epimysium: CT layer ensheated the entire muscle

Perimysium: CT layer ensheated each muscle bundle (fascicle)

Endomysium: CT layer ensheated each muscle fiber


Muscle fascicle

Blood vessels

Epimysium

Muscle fiber &endomysium

Perimysium

Epimysium, perimysium and endomysium extend at the muscle end forming tendon or aponeurosis

They protect the cells and provide passage for vessels and nerves Dr: Ahmed Saber Vet. Anat. 1. 2008


Muscle fiberPerimysium

Fascicle

Endomysium

Epimysium


Microscopic structures

Myofiber Myofibril

Myofilaments

Actin Myosin


Gross anatomy of skeletal muscle

1- anatomical parts:A- origin: • usually the proximal attachment of

muscle• Less movable part• Somtime more that one head (biceps)B- insertion:• Usually distal attachment• More movableC- belly:• The main balk of muscle between

origin and insertionDr: Ahmed Saber Vet. Anat. 1. 2008

2- skeletal muscle attachmenta) Boneb) Cartilagec) Deep fascia (indirectly to bone)d) Skin and superficial fasciae) Intermediate tendonf) No attachment (no origin & no insertion,

as orbicularis oris)


Also muscle attachment may beDirect attachment: the epimysium is fused to periosteum or perichondrium directlyIndirect attachment: epimysium extends as sheet like aponeurosis before attaching to bone, cartilage, fascia or other muscle


3- arrangements of skeletal muscle fibersBased on the angle between fiber and the line of pull


A- Parallel fibers:

1.Strap (sartorius)

2.Quadrates (quadratus femoris)

3.Fusiform (biceps brachi

Strap

Fusiform


B- oblique fibers (pennation)

The fibers attached to tendon at oblique angle (feather like)

1- unipennate: on one side of tendonex extensor digitorun longus M

2- bipennate : on opposite sides of tendon, ex rectus femoris M

3- multipennate: muscle fibers attached to several fibrous bands within the muscle, the bands join forming one tendon, ex deltoid M

4- Centripennate: one central tendon

Unipennate

Bipennate

Multipennate


C- circular fibers1- circular: no

attachment, around orifices, ex orbicularis oris (around mouth)

2- convergent: broad origin and pointed insertion, ex pectoralis major

Circular

Convergent

Functional types of muscles

1. Prime mover (Agonist muscles)– muscles most involved– cause joint motion through a specified

plane of motion when contracting

2. Antagonist muscles– located on opposite side of joint– have the opposite action to agonist


3. Synergist– assist in action of agonists– not necessarily prime movers for the action

4. Fixators (stabilozers)– Fix the joint


Blood and nerve supply

• Vessels and nerves pass through the connective tissue sheaths

• Bell is more vascular • One neuron supply

variable number of muscle fibers

• Motor unites = neuron+ muscle fiber innervated by this nerun



Accessory structures of skeletal muscle

1. Sesamoid bone– In course of some tendon – as superficial and deep flexor tendons– Protect the tendon– Decrease friction– Redirect the pull angle of the tendon


2. Fascia• is sheath of CT found

all over the body• Divided into• Internal fascia

(endothoracic, abdominaland pelvic)

• External fascia ( superficial and deep fascia)

skinSuperficial fascia

Deep fascia

Body wallInternal fascia

Bodycavity


3. Synovial sacIs sac filled with synoviaLocated between two structures to decrease

the friction between these structures1. Subtendinous2. Subcutaneous3. subligamentous

Bone

Tendon Synovial

sac


4. Tendon synovial sheath• elongated sac under the tendon• The edges of the sac become reflected

around the tendon• Consists of

– Outer fibrous layer– Double inner synovial– Parietal and visceral layer in between

small cavity filled with synovia• At edges meeting, the mesotendon present


tendon

Outer fibrous

Mesotendon

Parietal synoviallayer

Visceral synoviallayer

Synovial fluid

4. Tendon synovial sheath


5. Retinaculum• Transverse band of deep fascia around

carpal and tarsal joints • It fix the tendon and ligaments in its

position• As, flexor and extensor retinaculum of

carpus


Documents

PRINICIPLES OF MYOLOGY Def: science deals with muscles Dr: Ahmed SaberVet. Anat. 1. 2008 Skeletal muscles are the active part of locomotor system Smooth