1. The Muscular System Part C08
The Muscular System
Part C

2. Trunk Movements: Deep Back Muscles
The prime mover of back extension is the erector spinae
Erector spinae, or sacrospinalis, muscles consist of three columns on each side of the vertebrae – iliocostalis, longissimus, and spinalis
Lateral bending of the back is accomplished by unilateral contraction of these muscles
Other deep back extensors include the semispinalis muscles and the quadratus lumborum

3. Name: Erector Spinae Origin: Insertion: Primary action:
Posterior Muscles
Name: Erector Spinae
Origin:
Iliac crest, ribs 3-12, and vertebrae
Insertion:
Ribs thoracic / cervical vertebrae
Primary action:
Extends back

4. Name: Quadratus Lumborum
Origin:
iliac crest and iliolumbar ligament
Insertion:
Last rib and transverse processes of lumbar vertebrae
Primary action:
Alone, lateral flexion of vertebral column; Together, depression of thoracic rib cage

5. Trunk Movements: Deep Back Muscles
Figure 10.9d

6. Trunk Movements: Short Muscles
Four short muscles extend from one vertebra to another
These muscles are synergists in extension and rotation of the spine
Figure 10.9e

7. Muscles of Respiration
The primary function of deep thoracic muscles is to promote movement for breathing
External intercostals – more superficial layer that lifts the rib cage and increases thoracic volume to allow inspiration
Figure 10.10a

8. Name: External intercostals
Origin: lower border of ribs
Insertion: upper border of rib below
Primary action: Inhalation

9. Muscles of Respiration
Internal intercostals – deeper layer that aids in forced expiration
Diaphragm – most important muscle in inspiration
Figure 10.10a

10. Name: Internal intercostals
Origin: rib - inferior border
Insertion: rib - superior border
Primary action: hold ribs steady

11. Muscles of Respiration: The Diaphragm
Figure 10.10b

12. Name: Diaphragm
Primary action: Functions in breathing.
During inhalation, the diaphragm contracts, thus enlarging the thoracic cavity (the external intercostal muscles also participate in this enlargement).
When the diaphragm relaxes, air is exhaled by elastic recoil of the lung in conjunction with the abdominal muscles, which act as an antagonist paired with the diaphragm's contraction.

13. Muscles of the Abdominal Wall
The abdominal wall is composed of four paired muscles (internal and external obliques, transversus abdominis, and rectus abdominis), their fasciae, and their aponeuroses
Fascicles of these muscles run at right and oblique angles to one another, giving the abdominal wall added strength

14. Muscles of the Abdominal Wall
In addition to forming the abdominal wall, these muscles:
Are involved with lateral flexion and rotation of the trunk
Help promote urination, defecation, childbirth, vomiting, coughing, and screaming

15. Muscles of Abdominal Girdle
Name: External Oblique
Origin:
Lower 8 ribs
Insertion:
Iliac crest
Primary action:
Flexes and rotates vertebral column

16. Muscles of Abdominal Girdle
Name: Internal Oblique
Origin:
Iliac crest
Insertion:
Last 3 ribs
Primary action:
Paired muscles deep to external obliques
Flex and rotate vertebral column

17. Muscles of Abdominal Girdle
Name: Transverus abdominis
Origin:
Lower ribs and iliac crest
Insertion:
Pubis
Primary action:
Compresses abdominal contents

18. Muscles of Abdominal Girdle
Name: Rectus abdominis
Origin:
Pubis
Insertion:
Sternum and 5th to 7th rib
Primary action:
Flexes vertebral column

19. Muscles of the Abdominal Wall
Figure 10.11a

20. Muscles of the Abdominal Wall
Figure 10.11b

21. Muscles of the Abdominal Wall
Figure 10.11c

22. Muscles of the Pelvic Floor (Pelvic Diaphragm)
The pelvic diaphragm is composed of two paired muscles – levator ani and coccygeus
These muscles:
Close the inferior outlet of the pelvis
Support the pelvic floor
Elevate the pelvic floor to help release feces
Resist increased intra-abdominal pressure

23. Muscles Inferior to the Pelvic Floor
Two sphincter muscles allow voluntary control of urination (sphincter urethrae) and defecation (external anal sphincter)

24. Extrinsic Shoulder Muscles
Muscles of the thorax
Anterior: pectoralis major, pectoralis minor, serratus anterior, and subclavius
Posterior: latissimus dorsi, trapezius muscles, levator scapulae, and rhomboids
These muscles are involved with the movements of the scapula including elevation, depression, rotation, and lateral and medial movements
Prime movers of shoulder elevation are the trapezius and levator scapulae

25. Extrinsic Shoulder Muscles
Figure 10.13a

26. Extrinsic Shoulder Muscles
Figure 10.13b

27. Name: Pectoralis Major Origin:
Anterior Muscles
Name: Pectoralis Major
Origin:
Sternum, clavicle, & 1st to 6th rib
Insertion:
Proximal humerus
Primary action:
Adducts and flexes humerus

28. Name: Pectoralis minor
Origin:
third to fifth ribs, near their costal cartilages
Insertion: Scapula
Primary action:
Stabilizes scapula

29. Name: Serratus anterior
Origin: outer surface of upper 8 or 9 ribs
Insertion: costal aspect of medial margin of the scapula
Primary action:
protracts and stabilizes scapula, assists in upward rotation

30. Name: Subclavius
Origin: first rib
Insertion: subclavian groove of clavicle
Primary action:
depression of clavicle

31. Name: Latissimus Dorsi Origin:
Lower spine and iliac crest
Insertion:
Proximal humerus
Primary action:
Extends and adducts humerous

32. Name: Trapezius Origin: Insertion: Primary action:
Occipital bone and all cervical / thoracic vertebrae
Insertion:
Scapular spine and clavicle
Primary action:
Extends neck and adducts scapula

33. Name: Levator scapulae
Origin: C1 - C4 vertebrae
Insertion: scapula
Primary action:
Elevates scapula and tilts its glenoid cavity inferiorly by rotating scapula

34. Name: Rhomboids
Origin: C7 to T5 vertebrae
Insertion: scapula
Primary action:
Retracts the scapula and rotates it to depress the glenoid cavity. It also fixes the scapula to the thoracic wall.