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Learn about key muscles crossing the shoulder and elbow joints, their actions, and importance in movement. Discover prime movers, rotator cuff muscles, and synergists. Explore forearm muscle compartments and their functions.
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Muscles Crossing the Shoulder Joint • Nine muscles cross the shoulder joint to insert on and move the humerus
Muscles Crossing the Shoulder Joint • Some originate off the scapula; others originate off the axial skeleton • Three are prime movers of the arm • Pectoralis major • Latissimus dorsi • Deltoid • Actions include flexion, extension, adduction, abduction, and rotation of humerus
Muscles Crossing the Shoulder Joint • Four muscles are rotator cuff muscles • Supraspinatus • Infraspinatus • Teres minor • Subscapularis • Reinforce the capsule of the shoulder • Act as synergists and fixators • Two additional muscles are synergists: coracobrachialis and teres major
Clavicle Deltoid Sternum Pectoralis major Coracobrachialis Triceps brachii: Lateral head Long head Medial head Biceps brachii Brachialis Brachioradialis (a) Anterior view Figure 10.14a
Supraspinatus* Spine of scapula Deltoid (cut) Greater tubercle of humerus Infraspinatus* Teres minor* Teres major Triceps brachii: Lateral head Long head Latissimus dorsi Humerus Olecranon process of ulna Anconeus (b) Posterior view * Rotator cuff muscles Figure 10.14b
Muscles Crossing the Elbow Joint • Anterior flexor muscles • Brachialis and biceps brachii—chief forearm flexors • Brachioradialis—synergist and stabilizer
Clavicle Deltoid Sternum Pectoralis major Coracobrachialis Triceps brachii: Lateral head Long head Medial head Biceps brachii Brachialis Brachioradialis (a) Anterior view Figure 10.14a
Muscles Crossing the Elbow Joint • Posterior extensor muscles • Triceps brachii—prime mover of forearm extension • Anconeus—weak synergist
Supraspinatus* Spine of scapula Deltoid (cut) Greater tubercle of humerus Infraspinatus* Teres minor* Teres major Triceps brachii: Lateral head Long head Latissimus dorsi Humerus Olecranon process of ulna Anconeus (b) Posterior view * Rotator cuff muscles Figure 10.14b
Muscles of the Forearm • Actions: movements of the wrist, hand, and fingers • Most anterior muscles are flexors and insert via the flexor retinaculum • Most posterior muscles are extensors and insert via the extensor retinaculum
Muscles of the Forearm • Some forearm muscles act to produce pronation and supination of the forearm
Muscles of the Forearm • Pronators: pronator teres and pronator quadratus • Supinator: a synergist with the biceps brachii
Muscles of the Forearm: Anterior Compartment • Flexors • Flexor carpi radialis • Palmaris longus • Flexor carpi ulnaris • Flexor digitorum muscles (superficialis and profundus) • Flexor pollicis longus
Superficial transverse ligament of palm Palmar aponeurosis Flexor retinaculum Pronator quadratus Flexor digitorum superficialis Flexor pollicis longus Flexor carpi ulnaris Extensor carpi radialis longus Palmaris longus Flexor carpi radialis Brachioradialis Pronator teres Medial epicondyle of humerus Tendon of biceps brachii Medial head of triceps brachii Biceps brachii (a) Figure 10.15a
Tendon of flexor digitorum superficialis (cut) Tendon of flexor digitorum profundus Lumbricals Tendon of flexor pollicis longus Thenar muscles of thumb Tendon of flexor carpi ulnaris (cut) Pronator quadratus Flexor pollicis longus Flexor digitorum profundus Supinator (c) Figure 10.15c
Muscles of the Forearm: Posterior Compartment • Extensors • Extensor carpi radialis longus and brevis • Extensor digitorum • Extensor carpi ulnaris • Extensor pollicis brevis and longus • Extensor indicis • Abductor pollicis longus
Extensor expansion Tendons of extensor digitorum Tendons of extensor carpi radialis brevis and longus Extensor pollicis longus Extensor indicis Extensor pollicis brevis Extensor digiti minimi Abductor pollicis longus Extensor carpi ulnaris Extensor digitorum Flexor carpi ulnaris Extensor carpi radialis brevis Anconeus Insertion of triceps brachii Extensor carpi radialis longus Brachioradialis (a) Figure 10.16a
Interossei Extensor indicis Extensor pollicis brevis Extensor pollicis longus Abductor pollicis longus Supinator Anconeus Olecranon process of ulna (b) Figure 10.16b
Movements of the Wrist and Fingers • Flexion and extension • Abduction and adduction