Muscles of forearm

The muscles of the forearm are numerous, differ in the variety of functions. Most of the muscles are multiarticular, because they act on several joints: ulnar, radicular, wrist and distal joints of the hand and fingers.

When studying the anatomy of the muscles of the forearm, they are divided into separate groups according to anatomical and functional characteristics. According to the anatomical sign, the muscles of the forearm are divided into the anterior group (flexors) and the posterior (extensors).

The front group consists of 7 flexors of the hand and fingers and 2 pronators, the back - 9 extensors of the hand and fingers and the I muscle - the arch supports. Most of the muscles of the anterior group begin on the medial supramargle of the shoulder and fascia of the forearm, whereas the muscles of the posterior group originate on the lateral nadumyshke, as well as on the fascia of the forearm.

By functions distinguish:

1. muscles that provide movement in the proximal and distal lucheloid joints - supinator, round pronator, square pronator, brachial muscle;
2. muscles that provide movement in the wrist joint, as well as in the medium-wrist and carpal-metacarpal joints: radial and ulnar flexors of the wrist, elbow extensor of the wrist, long palmar muscle;
3. muscles - flexors and extensors of fingers - superficial flexor of fingers, deep flexor of fingers, extensor of fingers;
4. the muscles of the individual fingers are the long flexor of the thumb of the hand, the long extensor of the thumb of the hand, the long muscle, the thumb of the hand, the extensor of the index finger, the extensor of the little finger.

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Anterior muscle group of the forearm

The forearm muscles of the forearm (flexors) are arranged in 4 layers. Muscles are considered sequentially from the side of the radial bone in the direction of the ulnar bone. First, the surface layer is formed by the following muscles: the brachial muscle, the ulnar flexor of the wrist. In the second layer lies the superficial flexor of the fingers. The third layer consists of two muscles: the long flexor of the thumb (from the side of the radius, the deep flexor of the fingers (on the ulnar side) .The deepest, fourth layer is represented by a square pronator.

The first (superficial) sdom muscles of the forearm

The brachial muscle (m.brachioradialis) has a fleshy beginning on the lateral supracondylar ridge of the humerus and on the lateral intermuscular septum. At the level of the middle of the forearm, the muscular abdomen continues into a narrow flat tendon that passes under the tendons of the long distal muscle and the short extensor of the thumb of the hand and attaches to the lateral surface of the distal end of the radius. The pelvic muscle restrains the ulnar fossa from the lateral side.

Function: flexes the forearm at the elbow joint, rotates the radius, sets the brush on average between pronation and supination position.

Innervation: radial nerve (CV-СVIII).

Blood supply: radial artery, collateral and recurrent radial arteries.

Round pronator

(m.pronator teres) - the shortest of the muscles of the surface layer. The place of origin is divided into two unequal parts, the largest of which begins on the medial epicondyle of the shoulder, the fascia of the forearm, the medial intermuscular septum and the fascia plate separating the muscle from the radial flexor of the wrist. The smaller part starts deeper - on the coronoid process of the ulna. Between these two parts of the round pronator passes the median nerve. The muscle follows in the distal direction and outwards, limiting the ulnar fossa from the lower medial side. The muscle is attached by a flat tendon in the middle of the lateral surface of the radius.

Function: acting on the proximal and distal lucheloid joints, turns the forearm along with the wrist to the elbow (pronation), also participates in flexing the forearm at the elbow joint.

Innervation: the median nerve (CV-ThI).

Blood supply: humerus, ulnar and radial arteries.

Radial wrist flexor (m.flexor carpi radialis) begins on the medial condyle of the shoulder, on the fascia and the medial intermuscular septum of the shoulder. Approximately in the middle of the forearm, the muscle continues into the flat long tendon, which, passing under the retinaculum flexorum in the groove on the trapezoid bone, is attached to the base II (partially III) of the metacarpal bone.

Function: bends the wrist, acting together with the extensor of the hand, pulls the hand to the lateral side.

Innervation: the median nerve (CV-ThI).

Blood supply: humerus, ulnar and radial arteries.

The long palmar muscle (m.palmaris longus) begins on the medial epicondyle of the shoulder, on the fascia and the adjacent intermuscular septum of the forearm. It has a short muscular abdomen of spindle-shaped shape, which in the middle of the forearm passes into a flat, long tendon. The tendon passes over the brush over the flexor holder and is woven into the proximal part of the incense aponeurosis. Sometimes the muscle is absent.

Function: pulls the palmar aponeurosis, simultaneously participates in the bending of the hand.

Innervation: the median nerve (CV-ThI).

Blood supply: radial artery.

The ulnar flexor of the wrist

(m.flexor carpi ulnaris) begins with two heads - the shoulder and the elbow. The brachial head (caput brachiale) originates on the medial epicondyle and on the medial intermuscular septum of the shoulder. The ulnar (caput ulnare) begins deeper - on a deep leaf of the fascia of the forearm, on the medial edge of the ulnar process and the posterior edge of the ulna.

In the proximal third of the forearm, both heads are connected to the common abdomen. Next, the muscle is directed to the palmar surface of the hand along the medial edge of the forearm and passes into a long tendon that attaches to the pea-bones. Part of the tendon bundles continues below, forming a pea-hook-like ligament, and is attached to the hook of the hook-shaped bone and the pea-metacarpal ligament, and also to the base of the metacarpal bone.

Function: flexes the wrist (along with the wrist radial flexor); with a simultaneous contraction with the elbow extensor wrist leads to a brush.

Innervation: ulnar nerve (CVII-CVIII).

Blood supply: ulnar artery, upper and lower collateral ulnar arteries.

Second layer of forearm muscles

The superficial flexor of the fingers (m.flexor digitorum superficialis) begins with two heads - the brachial and radial. The heads are connected in the form of a bridge by a tendon stretch, which is crossed by the median nerve and the ulnar blood vessels from the front.

The cervical head (caput humeroulnare) is larger than the radial head. It starts on the medial epicondyle of the shoulder, the fascia of the forearm, the ulnar collateral ligament and on the medial edge of the coronoid process of the ulna. The smaller - a radial head (caput radiale) - begins on the proximal two-thirds of the anterior margin of the radius. In the proximal part of the forearm, both heads join together and form the common abdomen of the muscle, which in the middle of the forearm is divided into 4 parts, in the distal third of the forearm passing into the tendon. These tendons, passing along with the tendons of the deep flexor of the fingers through the carpal tunnel (under the flexor retainer and palmar aponeurosis), are directed to the palmar surface of the II-V fingers and attached to the base of the middle phalanx.

At the middle of the proximal phalanx, each tendon of the superficial flexor of the fingers is split into two legs, between which the corresponding tendon of the deep flexor of the fingers passes.

Function: flexes the middle phalanges of the II-V fingers (along with the fingers themselves), participates in the bending of the hand.

Innervation: the median nerve (CV-ThI).

Blood supply: radial and ulnar arteries.

Third layer of forearm muscles

The deep flexor of the fingers (m.flexor digitorum profundus) begins on the proximal two-thirds of the anterior surface of the ulna and on the interosseous membrane of the forearm. Four muscle tendons along with tendons of the superficial flexor of the fingers pass through the carpal tunnel. At the level of proximal phalanges, the tendons of the deep flexor of the fingers pass between the split tendons of the superficial flexor of the fingers and attach to the distal phalanges of the II-V fingers.

Function: bends the distal phalanges of II-V fingers (along with the fingers themselves); participates in flexion of the wrist in the wrist joint.

Innervation: the ulnar and median nerves (CV-ThI).

Blood supply: ulnar and radial arteries.

The long flexor of the thumb of the hand (m.flexor pollicis longus) begins on the front surface of the radius and the adjacent portion of the interosseous forearm from the level of tuberosity of the radius to the upper edge of the square pronator. The tendon of the muscle passes through the wrist canal in a separate synovial vagina. On the palm it passes between the two heads of the short flexor of the thumb of the hand and is attached to the base of the distal phalanx of the thumb.

Function: bends the distal phalanx of the thumb of the hand (along with the finger itself), participates in the bending of the brush.

Innervation: the median nerve (CV-ThI).

Blood supply: anterior interosseous artery.

Fourth layer of forearm muscles

A square pronator (m.pronator quadratus) is a plane muscle with transversely oriented fiber bundles. It is located under the tendons of the flexor of the fingers and wrists on the front surface of the lower third of the body of the ulnar, radial bones and the interosseous membrane of the forearm. The muscle begins at the anterior margin and the anterior surface of the lower third of the ulnar bone. Passing in the transverse direction, the muscle is attached to the front surface of the distal third of the body of the radius.

Function: penetrates the forearm and brush.

Innervation: the median nerve (CV-ThI).

Blood supply: anterior interosseous artery.

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Back muscle group of the forearm

The hind muscles of the forearm are divided into a superficial and a deep layer. The surface layer includes 5 muscles: a long radius of the extensor of the wrist, a short radius of the extensor of the wrist, the extensor of the fingers, the extensor of the little finger, the elbow extensor of the wrist. The deep layer also consists of 5 muscles: a supinator, a long muscle, a finger extending the thumb, a long extensor of the thumb of the hand, an extensor of the index finger.

Superficial layer of forearm muscles

The long radial extensor of the wrist (m.extensor carpi radialis longus) begins with muscle beams on the lateral epicondyle of the humerus and the lateral intermuscular septum of the shoulder. Here, the muscle is directly attached to the lateral surface of the elbow joint capsule. Distally throughout the forearm, the muscle occupies the space between the humerus muscle (front) and the short extensor of the wrist (behind). In the middle of the forearm, the muscle passes into a flat tendon, which, passing under the extensor retinaculum (retinaculum extensorum), attaches to the base of the metacarpal II bone.

Function: flexes the forearm (slightly), unbends the brush; with a simultaneous contraction with the radial flexor of the wrist, takes the hand laterally.

Innervation: radial nerve (CV-CVIII).

Blood supply: radial artery, collateral radial and recurrent radial artery.

The short radial extensor of the wrist (m.extensor carpi radialis brevis) begins on the lateral epicondyle of the humerus, the radial collateral ligament, on the fascia of the forearm. It is attached to the back surface of the base of the third metacarpal bone.

Function: Extends the brush; with a simultaneous contraction along with the radial flexor of the wrist, withdraws the wrist.

Innervation: radial nerve (CV-CVIII).

Blood supply: collateral radial and recurrent radial arteries.

Extensor of fingers

(m.extensor digitorum) is located medial to the radius extensors, begins on the lateral epicondyle of the humerus and on the fascia of the forearm. Near the wrist joint is divided into 4 tendons that pass under the extensor retainer in the common synovial vagina and attach to the back of the II-V fingers, forming tendon stretches. Middle tufts of tendon stretching are attached to the base of the middle phalanx, and lateral to the distal phalanx. At the level of the metacarpal bones, the extensor tendons of the extensors of the fingers are connected to each other obliquely by the oriented fibrous bundles - inter-suxal connections (connexus intertendineus).

Function, unbends II-V fingers; participates in the extension of the wrist in the wrist joint.

Innervation: radial nerve (CV-CVIII).

Blood supply: posterior interosseous artery.

The extensor of the little finger (m.extensor digiti minimi) has a common origin with the extensor of the fingers. The thin tendon of this muscle passes under the extensor retainer in a separate synovial vagina and is attached to the back of the little finger to the bases of its middle and distal phalanges (the tendons of the muscle are fused with the tendon of the extensor of the fingers).

Function: unbends the little finger.

Innervation: radial nerve (CV-CVIII).

Blood supply: posterior interosseous artery.

The ulnar extensor of the wrist (m.extensor carpi ulnaris) begins on the lateral epicondyle of the humerus, the capsule of the elbow joint, the fascia of the forearm. It is attached to the base of V metacarpal bone. The tendon of the muscle passes separately in the synovial vagina under the extensor retainer, occupying the groove on the posterior surface of the distal end of the ulna.

Function: Extends the brush. Acting in conjunction with the elbow wrist flexor, brings the brush.

Innervation: radial nerve (CVI-CVIII).

Blood supply: posterior interosseous artery. 

Deep layer of forearm muscles

The supinator (m.supinator) is almost completely covered with superficial muscles. The supinator starts on the lateral epicondyle of the humerus, the radial collateral ligament, the annular ligament of the radius and the crest of the arch support on the ulna.

The muscle passes obliquely in the lateral direction (embracing the radial bone behind and laterally) and is attached to the lateral surface of the proximal third of the radius.

Function: turns out the arch (supinator) the radial bone along with the brush.

Innervation: radial nerve (CVI-CVIII).

Blood supply: radiation, reflex and interosseous arteries.

The long muscle that removes the thumb of the hand (m.abductor pollicis longus) begins on the back surface of the ulna, the posterior surface of the radius and on the interosseous membrane of the forearm. Following from the place of its origin downwards and laterally, the muscle curves outside the radius with the tendons of the extensor carbide extensions lying on it. Further, the tendon of this muscle passes along with the tendon of the short extensor of the thumb of the hand in one synovial vagina under the lateral part of the extensor retainer and is attached to the back surface of the base of the first metacarpal bone.

Function: draws the thumb of the brush; participates in the lead of the brush.

Innervation: radial nerve (CV-CVIII).

Blood supply: radial artery, posterior interosseous artery.

Short extensor of the thumb of the hand

(m.extensor pollicis brevis) is found only in humans (it is genetically part of the long muscle that removes the thumb of the hand). It begins on the back surface of the radius, on the interosseous membrane of the forearm. The tendon of this muscle passes along with the tendon of the long muscle, which removes the thumb of the hand in one synovial vagina under the extensor retainer. It is attached to the base of the proximal phalanx of the thumb of the hand.

Function: unbends the proximal phalanx (with it and finger), withdraws the thumb of the hand.

Innervation: radial nerve (CV-CVIII).

Blood supply: radial artery, posterior interosseous artery.

The long extensor of the thumb of the hand (m.extensor pollicis longus) begins on the lateral side of the back surface of the ulna (within its middle third), on the interosseous membrane of the forearm. The tendon of the long extensor of the thumb of the hand passes under the extensor retainer in a separate synovial vagina, in the groove on the posterior surface of the radius bone. It is attached to the base of the distal phalanx of the thumb of the hand.

Function: unbends the thumb of the brush.

Innervation: radial nerve (CV-CVIII).

Blood supply: radial artery, posterior interosseous artery.

The extensor of the index finger (m.extensor indicis) begins on the back surface of the ulna and on the interosseous membrane of the forearm. The tendon of the muscle passes along with the tendons of the extensors of the fingers in the common synovial vagina under the extensor retainer. It is attached to the back surface of the proximal phalanx of the index finger (the tendon of the muscle is fused with the bundles of the extensor tendons of the fingers).

Function: unbends the index finger.

Innervation: radial nerve (CV-CVIII).

Blood supply: posterior interosseous artery.

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