The Muscular System Part C

1. The Muscular System Part C 08

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. 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. 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: 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.