Ch 9 Muscles Part 3

Question 1

Muscles Crossing the Shoulder Joint

Answer 1

Nine muscles cross shoulder joint; insert on and move humerus

Some originate from scapula; others from axial skeleton

Actions include flexion, extension, adduction

Three prime movers of arm:

Pectoralis major
Latissimus dorsi
Deltoid

Rotator cuff muscles act as synergists and fixators; originate on scapula; reinforce shoulder capsule; prevent dislocation

Supraspinatus
Infraspinatus
Teres minor
Subscapularis

Coracobrachialis and teres major - synergists

Question 2

Muscles Crossing the Elbow Joint

Answer 2

Posterior extensor muscles

Triceps brachii—prime mover of forearm extension
Anconeus—weak synergist

Question 3

Muscles of the Forearm

Answer 3

Actions - movements of wrist, fingers, thumb, pronation, supination

Most anterior muscles – flexors; insert via flexor retinaculum

Most posterior muscles – extensors; insert via extensor retinaculum

Pronator teres and pronator quadratus pronate forearm

Supinator - synergist with biceps brachii in forearm supination

Question 4

Muscles of the Forearm: Posterior Compartment

Answer 4

Extensors:
Extensor carpi radialis longus and brevis
Extensor digitorum
Extensor carpi ulnaris
Extensor pollicis brevis and longus
Extensor indicis
Abductor pollicis longus

Question 5

Movements of the Wrist and Fingers

Answer 5

Posterior compartment of forearm
(extends wrist and fingers);
innervated by radial nerve

Anterior compartment of forearm
(flexes wrist and fingers);
innervated by median or ulnar nerve

Question 6

Intrinsic Muscles of the Hand

Answer 6

Small weak muscles

• Lie entirely within palm of hand
• Control precise movements of metacarpals and fingers (e.g., threading a needle)
• Abductors and adductors of fingers
• Produce opposition—move thumb toward little finger

Question 7

Finger and Thumb Movements

Answer 7

Flexion-
Thumb—bends medially along palm
Fingers—bend anteriorly

Extension-
Thumb—points laterally
Fingers—move posteriorly

Question 8

Intrinsic Muscles of the Palm

Answer 8

Three groups-
Thenar eminence (ball of thumb) 

Hypothenar eminence (ball of the little finger)

Each of above groups has flexor, abductor, and opponens muscle

Midpalmar muscles – lumbricals and interossei extend fingers
Interossei muscles also abduct and adduct fingers