HUMAN ANATOMY – VOLUME 1

Fig. 108. Muscles of posterior region of forearm. Posterior aspect.

1 — brachioradialis; 2 — extensor carpi radialis longus; 3 — extensor carpi radialis brevis; 4 — abductor pollicis longus; 5 — extensor pollicis brevis; 6 — extensor digitorum; 7 — extensor pollicis longus; 8 — extensor retinaculum; 9 — tendinous chiasm; 10 — extensor carpi ulnaris; 11 — extensor digiti

minimi.

passes underneath the extensor retinaculum and is inserted into the base of the second metacarpal bone.

F u n c t i o n: It extends the wrist. When contracting simultaneously with the extensor carpi radialis brevis and the flexor carpi radialis, it abducts the wrist in the radiocarpal joint.

I n n e r v a t i o n: radial nerve.

B l o o d s u p p l y: collateral radial, recurrent radial and radial arteries.

The extensor carpi radialis brevis (m. exténsor cárpi radiális brévis) originates on the lateral epicondyle of humerus, the radial collateral ligament and the antebrachial fascia. It is inserted into the dorsal surface of the base of the third metacarpal bone.

F u n c t i o n: It extends the wrist. When contracting simultaneously with the extensor carpi radialis longus and the flexor carpi radialis, it abducts the wrist in the radiocarpal joint.

I n n e r v a t i o n: radial nerve.

B l o o d s u p p l y: collateral radial, recurrent radial and radial arteries.

The extensor digitorum muscle (m. exténsor digitórum) is situated medial of the radial extensors. It originates from the lateral epicondyle

and from the antebrachial fascia. At the level of the radiocarpal joint it is divided into four tendons, which pass underneath the extensor retinaculum and is inserted into the bases of middle phalanges and on the distal

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phalanges. At the level of the heads of the metacarpal bones these tendons are connected by tendinous intersections.

F u n c t i o n: This muscle extends fingers II–V and participates in extension of the wrist in the radiocarpal joint.

I n n e r v a t i o n: radial nerve.

B l o o d s u p p l y: posterior interosseous artery.

The extensor digiti minimi muscle (m. exténsor dígiti mínimi) has a common origin with the extensor of the fingers. Its long thin tendon passes under the extensor retinaculum, in its medial section. It is inserted into the dorsal surface of the bases of middle and distal phalanges of the little finger.

F u n c t i o n: Extends the little finger; participates in extending the wrist in the radiocarpal joint.

I n n e r v a t i o n: radial nerve.

B l o o d s u p p l y: posterior interosseous artery.

The extensor carpi ulnaris (m. exténsor cárpi ulnáris) originates on the lateral epicondyle of humerus, the posterior surface of ulna, the capsule of the elbow joint and the antebrachial fascia. It is inserted into the dorsal surface of the base of the fifth metacarpal bone.

F u n c t i o n: It extends the wrist. When contracting together with the flexor carpi ulnaris it adducts the wrist in the radiocarpal joint.

I n n e r v a t i o n: radial nerve.

B l o o d s u p p l y: posterior interosseous artery.

Deep layer of the posterior muscles of the forearm

The supinator muscle (m. supinátor) is almost completely covered by superficial muscles. It originates from the lateral epicondyle of the humerus, the radial collateral ligament, the annular ligament of the radius and on the supinator crest of the ulna. This muscle stretches obliquely laterally and is inserted into the lateral surface of upper third of the radial bone.

F u n c t i o n: It supinates the radius (together with the hand). I n n e r v a t i o n: radial nerve.

B l o o d s u p p l y: radial recurrent, recurrent interosseous and radial arteries.

The abductor pollicis longus muscle (m. abductor pollicis longus) originates on the posterior surfaces of the ulna and radius and the interosseous membrane of the forearm. It stretches downwards and laterally and curves about the radial bone and the tendons of the extensors carpi radialis. Its tendon, together with the tendon of the abductor pollicis longus, passes underneath the lateral part of the extensor retinaculum and is inserted into the base of the first metacarpal bone.

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F u n c t i o n: Abduction of the thumb. I n n e r v a t i o n: radial nerve.

B l o o d s u p p l y: posterior interosseous artery, radial artery.

The extensor pollicis brevis muscle (m. exténsor póllicis brevis) originates on the posterior surface of radius and the interosseous membrane of forearm. Its tendon passes through a common synovial sheath with the abductor pollicis longus and is inserted into the dorsal surface of the base of proximal phalanx of thumb.

F u n c t i o n: it extends the proximal phalanx of the thumb (thus straightening the thumb), and participates in abduction of the thumb.

I n n e r v a t i o n: radial nerve.

B l o o d s u p p l y: posterior interosseous artery, radial artery.

The extensor pollicis longus muscle (m. exténsor póllicic lóngus) originates from the lateral middle third of the posterior surface of the ulna and the interosseous membrane. Its tendon passes under the extensor retinaculum, through a groove on the posterior surface of radius. It is inserted into the dorsal surface of base of the distal phalanx of the thumb.

F u n c t i o n: Extension of the thumb. I n n e r v a t i o n: radial nerve.

B l o o d s u p p l y: posterior interosseous artery, radial artery.

The extensor indicis muscle (m. exténsor índicis) originates from the posterior surface of ulna and the interosseous membrane. Its tendon passes underneath the extensor retinaculum, together with the tendon of the extensor of fingers, and is inserted into the dorsal surface of the proximal phalanx of the index finger.

F u n c t i o n: Extension of the index finger. I n n e r v a t i o n: radial nerve.

B l o o d s u p p l y: posterior interosseous artery.

Questions for revision and examination

1.Into what groups are the muscles of the upper extremity divided according to their location and function?

2.Which muscles abduct the arm in the shoulder joint? Which muscles adduct it?

3.Name the supinator and pronator muscles of the upper extremity.

4.How many groups of muscles are there on the anterior side of the forearm? Name the muscles of each group.

5.What groups of muscles are there on the posterior side of the forearm? Name these muscles.

Muscles of the hand

Muscles of the hand are divided into three groups: muscles of the thenar eminence, muscles of the hypothenar eminence and the middle group of muscles (Fig. 109).

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Fig. 109. Muscles of hand. Palmar side.

1 — tendons of flexor digitorum superficialis; 2 — tendon of flexor carpi ulnaris; 3 — fascia of forearm (partially removed); 4 — pisiform; 5 — palmaris brevis; 6 — abductor digiti minimi; 7 — flexor digiti minimi brevis; 8 — opponens digiti minimi; 9 — lumbricals; 10 — fibrous sheath of digiti minimi; 11 — tendons of flexor digitorum profundus; 12 — tendons of flexor digitorum superficiale; 13 — dorsal interosseal muscle (1st); 14 — adductor pollicis; 15 — flexor pollicis brevis; 16 — abductor pollicis brevis; 17 — flexor retinaculum; 18 — tendo of

abductor pollicis longi; 19 — flexor pollicis longus.

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Muscles of the thenar eminence

The abductor pollicis brevis muscle (m. abdúctor póllicis brévis) is flat and is situated superficially (Fig.110). It originates from the scaphoid and trapezium bones and from the lateral region of the flexor retinaculum. The muscle stretches lateral and downwards to be inserted into the lateral edge of the base of the proximal phalanx of the thumb and the lateral edge of the tendon of extensor pollicis longus.

F u n c t i o n: Abduction of the thumb. I n n e r v a t i o n: median nerve.

B l o o d s u p p l y: superficial palmar branch of the radial artery.

Fig. 110. Muscles of thenar and hypothenar.

1 — adductor pollicis; 2 — flexor pollicis brevis; 3 — abductor pollicis longus; 4 — palmaris brevis; 5 — abductor digiti minimi; 6 — flexor digiti minimi.

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The opponens pollicis muscle (m. oppónens póllicis) is partially covered by the short abductor muscle of the thumb. Often if unites with the short flexor of the thumb. This muscle originates from the trapezium bone and the flexor retinaculum, and is inserted into the anterior surface of the first metacarpal bone.

F u n c t i o n: Opposition of the thumb to the other fingers. I n n e r v a t i o n: median nerve.

Blood supply: superficial palmar branch of the radial artery, superficial palmar arch.

The flexor pollicis brevis muscle (m. fléxor póllicis brévis) is partially covered by the short abductor of the thumb. It has a superficial and a deep heads. The s u p e r f i c i a l h e a d originates from the flexor retinaculum. The d e e p h e a d originates from the trapezium, trapezoid and second metacarpal bones. The muscle is inserted into the proximal phalanx of the thumb.

F u n c t i o n: It flexes the proximal phalanx of the thumb (thus bending the thumb) and participates in its adduction.

I n n e r v a t i o n: superficial head — the median nerve; deep head — the ulnar nerve.

B l o o d s u p p l y: superficial palmar branch of radial artery, deep palmar arch.

The adductor pollicis muscle (m. addúctor póllicis) is located in the middle of the thenar region. It lies beneath the tendons of the long flexors of fingers and the lumbrical muscles. It has an oblique and a transverse heads. Its o b l i q u e h e a d originates on the capitate bone and bases of II and III metacarpals. The t r a n s v e r s e h e a d originates from the anterior surface of the III metacarpal bone. The common tendon of this muscle is inserted into the base of the proximal phalanx of the thumb.

F u n c t i o n: It adducts the thumb to the index finger and participates in its flexion.

I n n e r v a t i o n: ulnar nerve.

B l o o d s u p p l y: superficial palmar arch, deep palmar arch.

Muscles of the hypothenar

The palmaris brevis muscle (m. pálmaris brévis) originates from the flexor retinaculum and is inserted into the skin of the medial edge of the hand. This muscle is not always present.

F u n c t i o n: It wrinkles the skin of the hypothenar region. I n n e r v a t i o n: ulnar nerve.

B l o o d s u p p l y: ulnar artery.

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The abductor digiti minimi brevis muscle (m. abdúctor dígiti mínimi) begins as a thin plate on the flexor retinaculum and the pisiform bone. It is inserted into the medial side of the proximal phalanx of the little finger.

F u n c t i o n: Abduction of the little finger. I n n e r v a t i o n: ulnar nerve.

B l o o d s u p p l y: deep palmar branch of ulnar artery.

The opponens digiti minimi muscle (m. oppónens dígiti mínimi) is a thin muscle, which originates on the flexor retinaculum and hook of hamate bone. It is inserted into the medial surface of the fifth metacarpal bone.

F u n c t i o n: opposition of the little finger (bringing it toward the thumb).

I n n e r v a t i o n: ulnar nerve.

B l o o d s u p p l y: deep palmar branch of the ulnar artery.

The flexor digiti minimi brevis muscle (m. fléxor dígiti mínimi) is a thin band; it originates from the hook of the hamate bone and the flexor retinaculum. It is inserted into the palmar surface of the proximal phalanx of the fifth finger.

F u n c t i o n: Flexion of the little finger. I n n e r v a t i o n: ulnar nerve.

B l o o d s u p p l y: deep palmar branch of the ulnar artery.

Middle group of the muscles of the hand

The lumbrical muscles (mm. lúmbricales) are four thin fusiform muscles, which are situated beneath the palmar aponeurosis. They originate from tendons of the deep flexor of the fingers. The first and second lumbrical muscles originate from the radial edge of tendons, directed towards the index and middle fingers; the third lumbrical originates from adjoining edges of the tendons, which are inserted into the middle and fourth fingers; the fourth lumbrical originates from adjoining edges of tendons of the fourth and little fingers. The lumbrical muscles stretch to the radial sides of II–V fingers and attach on the dorsal side of their proximal phalanges.

F u n c t i o n: They flex the proximal phalanges and straighten the middle and distal phalanges of fingers II–V.

I n n e r v a t i o n: first and second lumbricals—the median nerve; third and fourth — the ulnar nerve.

B l o o d s u p p l y: superficial palmar arch, deep palmar arch.

The palmar interossei muscles (mm. interóssei palmáres) are three muscles, situated on the carpal side of the hand, in the II, III and IV inter-

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metacarpal spaces. They originate from medial edges of the second and lateral edges of fourth and fifth metacarpals. They are inserted into the dorsal side of proximal phalanges of fingers II, IV and V.

F u n c t i o n: They adduct fingers II, IV and V to the third finger. I n n e r v a t i o n: ulnar nerve.

B l o o d s u p p l y: superficial palmar arch.

The dorsal interossei muscles (mm. interóssei dorsáles) are four pennate muscles, situated in the dorsal parts of the intermetacarpal spaces. Each originates by two heads on the adjacent sides of I–V metacarpals. The tendon of the first dorsal interosseous muscle is inserted into the radial side of proximal phalanx of the index finger; the second — on the radial side of the proximal phalanx of middle finger; the third — on the ulnar side of the proximal phalanx of the middle finger; and fourth — on the ulnar side of the proximal phalanx of the fourth finger (table 14).

F u n c t i o n: Abduction of the I, II, IV and V fingers from the third finger.

I n n e r v a t i o n: ulnar nerve.

B l o o d s u p p l y: deep palmar arch, dorsal metacarpal arteries.

Table 14. Muscles of the upper extremity.

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olecranon and antebrachial fascia

Second layer:

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