1MUSCLES OF THE HEAD AND THE TRUNK

2

Two headed-muscle, the key muscular landmark in neck Superior attachment: mastoid process of temporal bone and

superior nuchal line of occipital bone Inferior attachment:

sternal head: anterior surface of manubrium of sternum Clavicular head: superior surface of medial third of clavicle

Sternocleidomastoid (SCM)

Main action: Acting unilaterally, laterally flexes and

rotates the head and neck so the ear approaches the shoulder of the same side

Acting bilaterally, flex the neck

3

DEEP OR INTRINSIC BACK MUSCLES

extend from the pelvis to the skull specifically act on the vertebral

column, maintain posture and produce movements of vertebral column

enclosed by fascia Innervated by posterior rami of

spinal nerves

Common points

4

thoracolumbar fascia is an extensive fascial sheet that splits into anterior and posterior layers, enclosing the deep back muscles.

5Superficial layer - Splenius Muscles

Cover and hold the deep vertical muscles in position Origin: arises from nuchal ligament and

spinous processes of C7 T3 or T4 vertebrae Insertion:

Splenius capitis: mastoid process of temporal bone and lateral third of superior nuchal line of occipital bone

Splenius cervicis: transverse process of C1 C3 or C4 vertebrae

Main action: acting alone, laterally flex and rotate head

to the side of active muscles acting together, extend head and neck

6

Intermediate layer - Erector Spinae(Sacrospinalis)

the chief extensor of vertebral column, divides into three columns Iliocostalis: Lateral column Longissimus: Intermediate column Spinalis: Medial column Each column is divided regionally into

cervicis, thoracis, lumborum according to its superior attachment

Common origin: arises by a broad tendon from posterior part of iliac crest, posterior surface of sacrum, sacral and inferior lumbar spinous processes, and supro-iliac ligament Iliac crest

7

Insertion: Iliocostalis: fibers run superiorly to ribs and cervical

transverse processes

Intermediate layer - Erector Spinae(Sacrospinalis)

Spinalis: to spinous processes in the upper thoracic region and to skull

Longissimus: to ribs between tubercles and angles, to transverse processes in thoracic and cervical regions, and to mastoid process of temporal bone

8

Main action: powerful trunk extensor acting bilaterally, they extend vertebral column

and head, as back is flexed they control movement by gradually lengthening their fibers

Acting unilaterally, they laterally flex vertebral column

Intermediate layer - Erector Spinae(Sacrospinalis)

9 Three muscles Semispinalis superficial Multifidus deeper Rotatores deepest

Common feature: they originate from transverse

processes of vertebrae to spinous processes of more superior vertebrae.

They occupy the space between transverse and spinous processes

Deep Layer Transversospinal Muscle Group

Transverse section of back10

Semispinalis

Origin: arises from transverse processes of C4 T12 vertebrae

Insertion:fibers run superomedially to occipital bone and spinous processes in thoracic and cervical regions, spanning 4 6 segments

Main action:extend head and thoracic and cervical regions of vertebral column and rotate them contralaterally

11

Origin: arises from posterior aspects of sacrum and ilium, transverse processes of thoracic and lumbar vertebrae, and articular processes of the C4 - C7

Insertion:fibers pass superomedially to entire length of spinous processes of vertebrae above, spanning 2 - 4 segments

Main action: stabilizes vertebrae during local

movements of vertebral column Unilateral contraction rotates to

contralateral side

Multifidus

12

Origin: transverse processes of vertebrae

Insertion: pass superomedially to attach to the root of the spinous processes of the next one or two vertebrae superiorly, spanning 1 - 2 segments

Main action: as proprieception organs stabilize vertebrae and assists with

local extension and rotary movements of vertebral column

Rotatores

13

Minor Deep Layer

interspinal muscles connect spinous processes. They aid in extension and rotation

intertransverse muscles connect transverse processes. They aid in lateral flexion, and stabilize vertebral column when acting bilaterally

Levatores costarum elevate ribs, assisting inspiration and lateral flexion of vertebral column

14

occupy the intercostal spaces Superior layer: external intercostal Middle layer: internal intercostal Deepest layer: innermost intercostal

Superior attachment: inferior border of ribs Inferior attachment: superior border of ribs below

MUSCLES IN THORACIC WALL: Intercostal Muscles

Main action Elevate ribs: external intercostal

and probably innermost intercostal

depress ribs: internal intercostal

15

The muscle fibers run from inferior border of ribs to superior border of ribs below

External intercostal are continuous inferiorly with the external oblique muscles in the anterolateral abdominal wall

Internal intercostal run deep to and at right angles to the external intercostal and continuous with the internal oblique muscles in the anterolateral abdominal wall

External and Internal Intercostal Muscles

Action: External intercostal

inspiration, elevate ribs Internal intercostal

expiration, depress ribs

Internal intercostal

external intercostal

16

Similar to the internal intercostal in fibers running direction and are deep parts of them

The innermost intercostal muscles are separated from the internal intercostal by the intercostal nerves and vessels

Innermost Intercostal Muscles

17

MUSCLES OF ABODOMINAL WALL ANTERIOLATERAL WALL

Three flat muscles, external oblique, internal oblique, and transverse abdominal

Linea alba

All three flat muscles end anteriorly in strong aponeurosis. The aponeuroses of these muscles interlace at the linea alba

Linea alba (white line) is the fibrous band running vertically from the pubic symphysis to the xiphoid process and is the central attachment for all the abdominal muscles

18

External & Internal Oblique Muscle

Internal Oblique The intermediate muscle Origin: thoracolumbar

fascia, anterior two-thirds of iliac crest and lateral half of inquinal ligament

Insertion: The fibbers fan out anteromedially and insert to inferior borders of 10th 12th ribs, lineaalba, and pubis via conjoint tendon

Eternal Oblique The largest and most

superficial muscle Origin: external

surfaces of 5th-12th ribs Insertion: linea alba,

pubic tubercle, and anterior half of iliac crest

Common actions: compress and support abdominal viscera, flex and rotates trunk

19

Transverse Abdominal Muscle

The innermost of the three flat abdominal muscles

Origin: internal surfaces of 7th 12thcostal cartilages, thoracolumbar fascia, iliac crest, and lateral third of inquinal ligament

Insertion: linea alba with aponeurosis of internal oblique, superior ramus of pubis

Main action: Compress and support abdominal viscera

20

21

Two vertical muscles, rectus abdominisand pyramidalis

All two vertical muscles are within the rectus sheath that is the strong, incomplete fibrous compartment of the two vertical muscle. It is formed by the decussation and interweaving of the aponeuroses of the flat abdominal muscles

The rectus muscle is anchored by attachment to rectus sheath at tendinous intersections

MUSCLES OF ABODOMINAL WALL ANTERIOLATERAL WALL

Tendinous intersection

22

Rectus Abdominis Muscle

Origin: pubic symphysis and pubic crest

Insertion: Xiphoid process and 5th 7th costal cartilages

Most of the rectus abdominis is enclosed in the rectus sheath. Tendinous intersections (3 or more) anchor the rectus abdominis transversely

Main action: flexes trunk (lumbar vertebrae), compresses abdominal viscera, and stabilizes and controls tilt of pelvis

23

Functions and actions of the anterolateral abdominal muscles

Form a strong expendable support for the anterolateral abdominal wall

Protect the abdominal viscera from injury Compress the abdominal contents Help to maintain or increase the intra-abdominal

pressure, assisting expiration and producing the force required for defecation, micturition (urination), and parturition

Move the trunk. Flex vertebral column, bend vertebral column laterally, rotate vertebral column, and help to maintain posture

24

MUSCLES OF ABODOMINAL WALL POSTERIOR WALL -Quadratus lumborum,)

Pubic crest

Origin: medial half of inferior border of 12th rib and tips of lumbar transverse processes

Insertion: Iliolumbar ligament and iliac crest

Main action: extends and laterally flexes vertebral column; fixes 12th rib during respiration

25

Diaphragm

A dome-shaped musculotendinous partition separates the thoracic and abdominal cavities the chief muscle of inspiration It is divided into three parts based on peripheral

attachment, a sternal part, a costal part, and a lumbar part.

Principle Muscles Producing Movement of Cervical Intervertebral joints

Neck flexion Sternocleidomastoid

Neck extension Splenius Semispinalis capitis

and cervicis Multifidus Longissimus capitis trapezius

26

Lateral bending Iliocostalis cervicis Longiddimud csapitisand cervicis Splenius Intertraseversarii

Rotation Rotatores Multifidus Semispinalis capitis and cervicis Erector spinae Splenius cervicis sternocleidomastoid

27

Reading materials

Moore, KL, Essential Clinical Anatomy (5th ed.)

Neck muscles: p. 585-586 Back muscles: p. 295-303 Muscles of thoracic wall,

p.56-57 Muscles of abdomen: p.113-

115, p, 179, p, 184-185

Moore, KL, Essential Clinical Anatomy (4th ed.)

Neck muscles: p. 596-599 Back muscles: p. 301-310 Muscles of thoracic wall,

p.60-61 Muscles of abdomen: p.118-

122

28

Questions

1. Use the following terms to describe the actions and locations of back and abdominal muscles: origin, insertion, agonist and antagonist.

2. Use the following terms to describe the action of head, back and abdominal muscles: flexor, extensor, lateral flexor, and rotator.

3. Describe the locations and actions of the thoracic muscles.

4. Describe the locations and actions of neck muscles.5. Describe linea alba and rectus sheath.