The Muscular System Part D

1. The Muscular System Part D 08

2. Muscles Crossing the Shoulder Nine muscles cross the shoulder joint and insert into the humerus Prime movers include: Pectoralis major – arm flexion Latissimus dorsi and posterior fibers of the deltoid – arm extension Middle fibers of the deltoid – arm abduction

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

4. Name: Latissimus Dorsi Origin: Lower spine and iliac crest Insertion: Proximal humerus Primary action: Extends and adducts humerous Muscles Crossing the Shoulder

5. Muscles crossing the shoulder • Name: Deltoid • Origin: clavicle, acromion, spine of the scapula • Insertion: humerous • Primary action: • Flex, extend and adduct humerous

6. Muscles Crossing the Shoulder Figure 10.14a

7. Muscles Crossing the Shoulder Figure 10.14d

8. Muscles Crossing the Shoulder Rotator cuff muscles – supraspinatus, infraspinatus, teres minor, and subscapularis Function mainly to reinforce the capsule of the shoulder Secondarily act as synergists and fixators The coracobrachialis and teres major: Act as synergists Do not contribute to reinforcement of the shoulder joint

9. Muscles crossing the shoulder Name: Supraspinatus Origin: Scapula Insertion: Humerus Primary action: abduct and stabilize humerus

10. Muscles crossing the shoulder Name: Infraspinatus Origin: Scapula Insertion: Humerus Primary action: Lateral rotation of arm and stabilizes humerus

11. Name: Teres minor Origin: scapula Insertion: humerus Primary action: laterally rotates arm Muscles crossing the shoulder

12. Name: Subscapularis Origin: Subscapular fossa Insertion: humerus Primary action: rotates medially humerus; stabilizes shoulder Muscles crossing the shoulder

13. Name: coracobrachialis Origin: coracoid process of scapula Insertion: medial humerus Primary action: adducts humerus , flexes the arm at glenohumeral joint Muscles crossing the shoulder

14. Name: Teres major Origin: posterior aspect of the inferior angle of the scapula Insertion: Humerus Primary action: Internal rotation (medial rotation) of the humerus Muscles crossing the shoulder

15. Muscles Crossing the Shoulder Figure 10.14a

16. Muscles Crossing the Shoulder Figure 10.14d

17. Muscles Crossing the Shoulder Figure 10.14c

18. Muscles Crossing the Elbow Forearm extension The triceps brachii is the prime mover of forearm extension The anconeus is a weak synergist Forearm flexion Brachialis and biceps brachii are the chief forearm flexors The brachioradialis acts as a synergist and helps stabilize the elbow

19. Muscles crossing the elbow Name: triceps brachii Origin: long head: infraglenoid tubercle of scapula lateral head: posterior humerus medial head: posterior humerus Insertion: olecranon process of ulna Primary action: extends forearm, long head adducts shoulder

20. Muscles crossing the elbow Name: Anconeus Origin: lateral epicondyle of the humerus proximally Insertion: lateral surface of the olecranon process and the superior part of the posterior ulna distally Primary action: assists in extension of the forearm stabilizes the elbow during pronation and supination

21. Muscles crossing the elbow Name: brachialis Origin: anterior surface of the distal end of humerus Insertion: coronoid process and the tuberosity of the ulna Primary action: flexion at elbow joint

22. Muscles crossing the elbow Name: biceps brachii Origin: short head: coracoid process of the scapula. long head: supraglenoid tubercle Insertion: radial tuberosity Primary action: flexes elbow and supinates forearm

23. Muscles crossing the elbow Name: brachioradialis Origin: Lateral supracondylar ridge of the humerus Insertion: Distal radius (Radial styloid process) Primary action: flexion of forearm

24. Muscles of the Forearm The two functional forearm muscle groups are: those that cause wrist movement, and those that move the fingers and the thumb These muscles insert via strong ligaments called flexorand extensor retinacula Most anterior muscles are flexors, and posterior muscles are extensors The pronator teres and pronator quadratus are not flexors, but pronate the forearm The supinator muscle is a synergist with the biceps brachii in supinating the forearm

25. Muscles of the Forearm: Anterior Compartment These muscles are primarily flexors of the wrist and fingers Figure 10.15a

26. Muscles of the Forearm: Anterior Compartment Figure 10.15b, c

27. Muscles of the Forearm: Posterior Compartment These muscles are primarily extensors of the wrist and fingers Figure 10.16a

28. Muscles of the Forearm: Posterior Compartment These muscles are primarily extensors of the wrist and fingers Figure 10.16b

29. Muscle Action of the Arm: Summary The posterior extensor and anterior flexor muscles are shown Figure 10.17a

30. Muscle Action of the Forearm: Summary Posterior extensors of the wrist and fingers, and anterior flexor muscles are shown Figure 10.17b

31. Intrinsic Muscles of the Hand These small muscles: Lie in the palm of the hand (none on the dorsal side) Move the metacarpals and fingers Control precise movements (e.g., threading a needle) Are the main abductors and adductors of the fingers Produce opposition – move the thumb toward the little finger

32. Intrinsic Muscles of the Hand Figure 10.18a

33. Intrinsic Muscles of the Hand Figure 10.18b

34. Finger and Thumb Movements Flexion Thumb – bends medially along the palm Fingers – bend anteriorly Extension Thumb – points laterally Fingers – move posteriorly

35. Intrinsic Muscles of the Hand: Groups There are three groups of intrinsic hand muscles The thenar eminence (ball of the thumb) and hypothenar eminence (ball of the little finger) – each have a flexor, an abductor, and an opponens muscle The midpalm muscles, the lumbricals and interossei, extend the fingers The interossei also abduct and adduct the fingers

36. Intrinsic Muscles of the Hand: Groups Figure 10.18c, d