Upper forearm muscle. Forearm muscles

05.03.202127.05.2017

Hello! The most difficult bone to study is, of course, the temporal bone. The heaviest part of the peripheral nervous system These are the cranial nerves. But the hardest part of myology in normal anatomy- forearm, that's indisputable. The forearm strikes students during lectures; sometimes there is simply no idea how all this can be learned.

But it is possible to learn, and very quickly. The main thing is to place reference points and clearly imagine the entire anatomical picture as a whole.

First of all, let's remember that the hand needs to be considered only in its physiological position. We will have ahead large number schemes, at your seminars you will also answer on tablets and drugs - so, everywhere, absolutely everywhere, the hands are in the correct physiological position. That is inside palms forward and nails back. Like this illustration:

And one more important thing for us. Everything on the arm in the physiological position in front is the flexors. Everything behind is extensors. When we pull ourselves up reverse grip– the biceps works, and it’s in the front. When we bring our palm closer to the shoulder, bending the arm at the elbow, we are using the biceps. It’s the same with the forearm – the flexor muscles are located in front, let’s start with them

MUSCLES OF THE FOREARM, ANTERIOR GROUP:

Surface layer.

1. Our main landmark here - powerful, large brachioradialis muscle(musculus brachioradialis). Her special features: she is very wide, powerful, compared to the rest of her muscles. It occupies the most lateral position (if the arm is positioned physiologically).

Don't forget that the radius comes from elbow joint to the wrist on the side of the thumb. This is exactly how we show the brachialis muscle. The largest, most lateral - just a fairy tale. Definitely the main landmark that is immediately visible on any tablet or preparation.

Location: starts from the humerus, attaches to the radius (this is easy to remember by its name);
Function: very typical for this entire muscle group. Namely, bending the arm at the elbow joint.

2. Pronator teres(musculus pronator teres). Using our first landmark, we can easily identify the pronator teres (where it is round is a question for the ancient anatomists). It is he who, with the brachioradialis, the same widest and most lateral muscle, forms the letter Y. It’s very easy to remember.

Location: starts from the medial epicondyle of the humerus, as well as from the coronoid process of the ulna (the muscle is quite wide and short). Attaches to the center of the radius on the lateral side.
Function: flexes the arm at the elbow joint and also pronates the forearm.

By the way, there is great way remember what supination and pronation are. Imagine that you are carrying a bowl of soup. If your palm is in the same position as when holding a bowl of SOUP, it is Suppinated. If you turn your palm over, the soup SPILLS and Pronation occurs.

3. Remember this Y, which is formed by our main guideline - brachioradialis muscle(the most lateral, very large) and the pronator teres, which is adjacent to it at an acute angle. But it fits very tightly to the pronator teres flexor carpi radialis(musculus flexor carpi radialis). It certainly doesn't look particularly lateral, but we'll have another flexor to which the flexor carpi radialis will be truly lateral.

Location: Originates from the medial epicondyle of the humerus and inserts on the second metacarpal bone.
Function: As the name suggests, this muscle flexes the wrist

4. We are talking about this muscle - flexor ulnaris wrists(musculus flexor carpi ulnaris). It is the most medial muscle of the superficial layer of the anterior group. Long, thin and most medial. Pretty simple, right?

Location: Starts from the already familiar medial epicondyle of the humerus, as well as from back surface ulna (the muscle has two heads). Attaches to the hamate bone.
Function: bends the hand

5. So, we have two flexors - radial and ulnar. And between them will pass long palmaris muscle (musculus palmaris longus). I specifically chose to leave the flexor radialis and ulnaris colored because they are great reference points for locating the palmaris longus muscle. I marked the palmaris longus muscle itself with a red dotted line.

An important feature of the palmaris longus muscle is that it is woven into the wide palmar aponeurosis. You can find the palmaris longus muscle on the specimen by first identifying the aponeurosis itself, and then, looking a little more proximally, the elongated palmaris longus tendon.

Location: starts from the medial epicondyle of the humerus, attaches, as we have already found out, to the wide palmar aponeurosis.
Function: bends the hand. Don’t be confused, this muscle bends the hand, not the palm.

So, what will help us remember all this, what are the loopholes, life hacks and patterns in this topic?

Correct landmarks. We start from the brachioradialis muscle. Very large, the most lateral muscle of the entire group. Then we find the pronator teres - the same muscle that connects to the brachioradialis in the shape of the letter Y. Then we find two flexors - the radius and the ulna. Between them (also an excellent landmark, by the way) runs the long palmaris muscle with a very characteristic direction directly to the center of the palm, to the palmar aponeurosis.
Titles. Pronator - pronates, the carpal flexors, oddly enough, bend the wrists. U three muscles Of the five, the function is in the name.
Pattern of location. All muscles, except the brachioradialis, begin from the medal epicondyle of the humerus.

Lexical minimum.

The traditional list of Latin names of muscles that you should easily display on tablets, as well as explain their function and location:

Musculus brachioradialis;
Musculus pronator teres;
Musculus flexor carpi radialis;
Musculus flexor carpi ulnaris;
Musculus palmaris longus

According to their function, they are divided into flexors and extensors, some of them flex and extend the entire hand, while others - the fingers. In addition, there are also pronators and supinators, which produce the corresponding movements of the radius. According to their position, all these muscles fall into two groups: the anterior one, which includes flexors and pronators, and the posterior one, consisting of extensors and supinators.

Each group is composed of superficial and deep layers. The superficial layer of the muscles of the anterior group originates in the region of the medial epicondyle of the shoulder, the same layer of the posterior group originates in the region of the lateral epicondyle. The deep layer of both groups in its main part no longer finds a place of attachment on the epicondyles, but originates on the bones of the forearm and on the interosseous membrane.
The final attachments of the flexors and extensors of the hand are located at the bases of the metacarpal bones, and the same muscles going to the fingers are attached to the phalanges, with the exception of the abducens longus. thumb muscle attached to the first metacarpal bone.

The pronators and supinators are attached to the radius. The muscles of the forearm closer to the shoulder consist of fleshy parts, while towards the hand they turn into long tendons, as a result of which the forearm has the shape of a cone, flattened from front to back.

Anterior muscle group of the forearm

Superficial layer of forearm muscles consists of the following muscles.

1. M. pronator teres, round pronator, starts from the medial epicondyle of the humerus and tuberositas ulnae and attaches to the lateral surface of the radius immediately above its middle.

Function. Pronates the forearm and participates in its flexion. (Inn. CVI-VII. N. medianus.)

2. M. flexor carpi radialis, flexor carpi radialis lies along the medial edge of the pronator teres. It starts from the medial epicondyle of the humerus and attaches to the base of the second metacarpal bone.

Function. It flexes the hand and can also move it to the radial side in combination with other muscles. (Inn. CVI-VII N. medianus.)

3. M. palmaris longus, long palmaris muscle, lies medially from the previous one and starts from the medial epicondyle of the shoulder. Its short fusiform abdomen passes very high into a thin long tendon, which, on top of the retinaculum flexorum, passes into the palmar aponeurosis, aponeurosis palmaris. This muscle is often absent.

Function. Pulls the palmar aponeurosis and bends the hand. (Inn. СVII - ThI N. medianus.)

4. M. flexor carpi ulndris, flexor carpi ulnaris, is located on the ulnar edge of the forearm, originating from the medial epicondyle of the shoulder, and is attached to the pisiform bone, which is a sesamoid for it, and further to the os hamatum (in the form of lig. pisohamatum) and the fifth metacarpal bone (in the form of lig. pisometacarpeum).

Function. Together with m. flexor carpi radialis bends the hand and also adducts it (together with the m. extensor carpi ulnaris). (Inn. CVII - ThI. N. ulnaris, sometimes n. medianus)

5. M. flexor digitorum superflcialis, superficial flexor digitorum, lies deeper than the four muscles described. It starts from the medial epicondyle of the humerus, processus coronoideus of the ulna and the upper part of the radius.
The muscle is divided into four long tendons that descend from the forearm through canalis carpalis on the palm, where they go to the palmar surface of the II-V fingers.
At the level of the body of the proximal phalanx, each of the tendons is divided into two legs, which, diverging, form a gap, hiatus tendineus, for the passage of the tendon, the deep flexor, with which they intersect ( chiasma tendinum), and are attached to the palmar surface of the base of the middle phalanx.

Function. Flexes the proximal and middle phalanx of the fingers (except for the thumb), as well as the entire hand. (Inn. CVII-ThI N. medianus.)

Deep layer of forearm muscles:

6. M. flexor pollicis longus, long flexor of the thumb, starts from the anterior surface of the radius distally from the tuberositas radii and partly from the medial epicondyle of the humerus.
The long tendon passes under the retinaculum flexorum on the palm and is directed in the groove between both heads of the m. flexor pollicis brevis to the base of the second phalanx of the thumb.

Function. Flexes the nail phalanx of the thumb, as well as the hand. (Inn. N. medianus.)

7. M. flexor digitorum profundus, deep flexor of the fingers, originates from the ulna and interosseous membrane. Its four tendons, extending from the body of the muscle in the middle of the forearm, pass through the canalis carpalis into the palm, lying under the tendons of the superficial flexor, and then go to the II-V fingers, and each of these tendons penetrates the hiatus tendineus between the legs of the tendon m. flexor digitorum superficalis, forming a decussation with it, and is attached to the distal phalanx.

Function. Flexes the middle and distal phalanges of the II-V fingers, and also participates in flexion of the hand. (Inn. СVII - ThI. N. medianus et n. ulnaris.)

8. M. pronator quadratus, square pronator, is a flat quadrangular muscle located directly on both bones of the forearm and on the interosseous membrane, immediately above wrist joints. Starting from the palmar surface of the ulna, it is attached to the palmar side of the radius.

Function. It is the main pronator of the forearm, and the teres is an auxiliary one. (Inn. CIV - ThI N. medianus.)

Video lesson on the anatomy of the forearm muscles

The anatomy of the forearm muscles is disassembled on a cadaveric specimen.

The muscles of the forearm are divided into posterior and anterior groups, each of which has a superficial and deep layer.

Front group

Surface layer

Pronator teres(m. pronator teres) (Fig. 111, 115, 116, 117, 125) pronates the forearm (rotates it forward and inward so that the palm turns posteriorly (downward) and the thumb inward to the median plane of the body) and participates in its bending. Fat and short muscle, consisting of two heads. The large, humeral head (caput humerale) starts from the medial epicondyle of the humerus and the medial intermuscular septum of the brachial fascia, and the small, ulnar head (caput ulnare) starts from the coronoid process of the ulnar tuberosity. Both heads, connecting, form a flattened abdomen. The attachment point is the middle third of the radius.

Brachioradialis muscle(m. brachioradialis) (Fig. 90, 111, 113, 114, 115, 116, 118, 121, 125) flexes the forearm and takes part in both pronation and supination of the forearm (rotates it so that the palm turns anteriorly (up), and the thumb is outward from the median plane of the body) of the radius. The muscle has a fusiform shape, starts from the humerus above the lateral epicondyle and from the lateral intermuscular septum of the brachial fascia, and is attached at the lower end of the body of the radius.

Flexor carpi radialis(m. flexor carpi radialis) (Fig. 90, 115, 121, 125) bends and partially pronates the hand. A long, flat, bipennate muscle, the proximal part of which is covered by the aponeurosis of the biceps brachii muscle. Its point of origin is located on the medial epicondyle of the humerus and fascia of the forearm, and its attachment point is on the base of the palmar surface of the second metacarpal bone.

Palmaris longus muscle(m. palmaris longus) (Fig. 115, 125) stretches the palmar aponeurosis and takes part in flexion of the hand.

A characteristic feature of the muscle structure is a short fusiform abdomen and a long tendon. It begins on the medial epicondyle of the humerus and fascia of the forearm, medially to the flexor carpi radialis, and is attached to the palmar aponeurosis (aponeurosis palmaris).

Flexor carpi ulnaris(m. flexor capiti ulnaris) (Fig. 90, 115, 116, 118, 121, 125) bends the hand and takes part in its adduction. Characterized by a long abdomen, thick tendon and two heads. The humeral head has its origin at the medial epicondyle of the humerus and the fascia of the forearm, and the ulnar head has the olecranon and the upper two-thirds of the ulna. Both heads are attached to the pisiform bone, some of the bundles are attached to the hamate and V metacarpal bones.

Flexor digitorum superficialis(m. flexor digitorum superficialis) (Fig. 115, 116, 120, 125) bends the middle phalanges of the II-V fingers. This vastus muscle covered by the flexor carpi radialis and palmaris longus muscle and consists of two heads. The humeroulnar head (caput humeroulnare) starts from the medial epicondyle of the humerus and ulna, the radial head (caput radiale) - from the proximal part of the radius. The heads form a single abdomen with four tendons, which pass onto the hand and are each attached by two legs to the base of the middle phalanges of the II-V fingers of the hand.

Deep layer

Flexor pollicis longus(m. flexor pollicis longus) (Fig. 115, 116, 120) bends the distal phalanx of the first (thumb) finger. A long, flat, single-pinnate muscle, its origin point is the upper two-thirds of the anterior surface of the radius, the interosseous membrane (membrana interossea) (Fig. 117, 125) between the radius and ulna and partially the medial epicondyle of the humerus. Attached at the base of the distal phalanx of the thumb.

Flexor digitorum profundus(m. flexor digitorum profundus) (Fig. 116, 119, 120, 125) bends the entire hand and the distal phalanges of the II-V fingers. It is characterized by a highly developed flat and wide abdomen, the origin of which is located on the upper two-thirds of the anterior surface of the ulna and the interosseous membrane. The attachment point is located at the base of the distal phalanges of the II-V fingers.

Pronator quadratus(m. pronator quadratus) (Fig. 116, 117, 120, 121) rotates the forearm inward (pronates). The muscle is a thin quadrangular plate located in the area of the distal ends of the bones of the forearm. It begins on the medial edge of the body of the ulna and attaches to the lateral edge and anterior surface of the radius.

Back group

Surface layer

Extensor carpi radialis longus(m. extensor carpi radialis longus) (Fig. 90, 113, 114, 116, 118, 122, 123, 125) bends the forearm at the elbow joint, extends the hand and takes part in its abduction. The muscle has a spindle-shaped shape and is distinguished by a narrow tendon, significantly longer than the abdomen. Upper part The muscle is covered by the brachioradialis muscle. Its point of origin is located on the lateral epicondyle of the humerus and the lateral intermuscular septum of the brachial fascia, and its attachment point is on the dorsal surface of the base of the second metacarpal bone.

Extensor carpi radialis brevis(m. extensor carpi radialis brevis) (Fig. 90, 122, 123, 125) extends the hand, retracting it slightly. This muscle is slightly covered by the extensor carpi radialis longus, originates from the lateral epicondyle of the humerus and the fascia of the forearm, and is attached to the dorsum of the base of the third metacarpal bone.

Rice. 115. Shoulder muscles and shoulder girdle front view 1 - biceps brachii; 2 - brachialis muscle; 4 - aponeurosis of the biceps brachii muscle; 5 - pronator teres; 6 - brachioradialis muscle; 7 - flexor carpi radialis; 8 - flexor carpi ulnaris; 9 - palmaris longus muscle; 10 - superficial flexor of the fingers; 11 - flexor pollicis longus; 12 - short palmaris muscle; 13 - palmar aponeurosis
Rice. 116. Muscles of the forearm front view 1 - brachialis muscle; 2 — instep support; 3 - tendon of the biceps brachii; 4 - extensor carpi radialis longus; 5 - deep flexor of the fingers; 6 - brachioradialis muscle; 7 - flexor pollicis longus; 8 - pronator teres; 9 - flexor carpi ulnaris; 10 - pronator quadratus; 11 - muscle opposing the thumb; 12 - muscle adducting the little finger; 13 - short flexor pollicis; 14 - tendons of the deep flexor of the digitorum; 15 - flexor pollicis longus tendon; 16 - tendons of the superficial flexor of the fingers
Rice. 117. Muscles of the forearm front view 1 - pronator teres; 2 - tendon of the biceps brachii; 3 — instep support; 4 - interosseous membrane; 5 - pronator quadratus
Rice. 118. Muscles of the forearm, rear view 1 - brachioradialis muscle; 2 — triceps shoulder; 3 - extensor carpi radialis longus; 4 - elbow muscle; 5 - flexor carpi ulnaris; 6 - extensor finger; 7 - extensor carpi ulnaris; 8 - extensor of the little finger; 9 - abductor pollicis longus muscle; 10 - short extensor pollicis; 11 - extensor retinaculum; 12 - extensor pollicis longus; 13 - finger extensor tendons
Rice. 119. Muscles of the forearm, rear view 1 - instep support; 2 - deep flexor of the fingers; 3 - abductor pollicis longus muscle; 4 - extensor pollicis longus; 5 - short extensor pollicis; 6 - extensor of the index finger; 7 - extensor retinaculum; 8 - extensor tendon

Extensor digitorum(m. extensor digitorum) (Fig. 90, 118, 119, 122, 123, 125) extends the fingers and takes part in the extension of the hand. The muscle belly has a fusiform shape, the direction of the bundles is characterized by a bipinnate shape. Its point of origin is on the lateral epicondyle of the humerus and the fascia of the forearm. In the middle of its length, the abdomen turns into four tendons, which on the back of the hand turn into tendon stretches, and with their middle part they are attached to the base of the middle phalanges, and with their lateral parts - to the base of the distal phalanges of the II-V fingers.

Extensor of the little finger(m. extensor digiti minimi) (Fig. 90, 118, 122, 123) extends the little finger. A small fusiform muscle that begins on the lateral epicondyle of the humerus and attaches to the base of the distal phalanx of the fifth finger (little finger).

Extensor carpi ulnaris(m. extensor capiti ulnaris) (Fig. 90, 118, 122, 123, 125) extends the hand and moves it to the ulnar side. The muscle has a long fusiform belly, begins on the lateral epicondyle of the humerus and fascia of the forearm, and is attached to the base of the dorsum of the fifth metacarpal bone.

Deep layer

Arch support(m. supinator) (Fig. 116, 117, 119, 125) rotates the forearm outward (supinates) and takes part in straightening the arm at the elbow joint. The muscle has the shape of a thin diamond-shaped plate. Its point of origin is on the crest of the supinator of the ulna, the lateral epicondyle of the humerus and the capsule of the elbow joint. The attachment point for the instep support is located on the lateral, anterior and posterior sides of the upper third of the radius.

Abductor pollicis longus muscle(m. abductor pollicis longus) (Fig. 90, 118, 119, 123, 125), abducts the thumb and takes part in abduction of the hand. The muscle is partially covered by the extensor digitorum and the short extensor carpi radialis, and has a flat bipinnate belly, which turns into a thin long tendon. It begins on the posterior surface of the ulna and radius and attaches to the base of the first metacarpal bone.

Extensor pollicis brevis(m. extensor pollicis brevis) (Fig. 90, 118, 119, 122, 123) abducts the thumb and extends its proximal phalanx. The origin of this muscle is located on the posterior surface of the neck of the radius and the interosseous membrane, the attachment point is on the base of the proximal phalanx of the thumb and the capsule of the first metacarpophalangeal joint.

Extensor pollicis longus(m. extensor pollicis longus) (Fig. 118, 119, 123, 125) extends the thumb, partially abducting it. The muscle has a fusiform belly and a long tendon. The point of origin is on the posterior surface of the body of the ulna and the interosseous membrane, the attachment point is on the base of the distal phalanx of the thumb.

Extensor index finger(m. extensor indicis) (Fig. 119, 123, 125) extends the index finger. This muscle sometimes missing. It is covered by the extensor digitorum and has a narrow, long, fusiform abdomen. It begins on the posterior surface of the body of the ulna and the interosseous membrane, and is attached to the dorsal surface of the middle and distal phalanges of the index finger.

The muscles of the forearm are divided into anterior and posterior groups. The function of the anterior group of muscles is flexors, the posterior group is extensors. The anterior muscle group is located in four layers, the rear - in two layers.

Anterior muscle group of the forearm. First layer

Brachioradialis muscle (brachioradialis) located on the lateral edge of the forearm, starting from the lateral epicondyle of the humerus. Attaches to the styloid process of the radius.

Function: flexes the forearm, rotates the radius.

Pronator teres (pronator teres) begins with two heads: superficial - from the internal epicondyle of the humerus and deep - from the coronoid process of the ulna. Attaches to the lateral surface of the radius.

Function: pronates the hand and flexes the forearm.

Flexor carpi radialis (flexor carpi radialis) starts from the internal epicondyle of the humerus, passes into a tendon that passes under the flexor retinaculum in the groove of the trapezius bone and attaches to the base of the 2nd metacarpal bone.

Function: bends the radial edge of the hand, takes part in pronation of the hand.

Melon palmar muscle (t. palmaris longus) starts from the internal epicondyle of the humerus, passes into a thin tendon that passes over the flexor retinaculum and is attached to the palmar aponeurosis.

Function: strains the palmar aponeurosis, participates in flexion of the hand.

Flexor carpi ulnaris (flexor carpi ulnaris) starts from the internal epicondyle of the humerus, the fascia of the forearm (humeral head) and from the olecranon process, the posterior edge of the ulna (ulnar head). Attaches to the pisiform bone.

Function: bends the ulnar edge of the hand and slightly supinates it.

Anterior muscle group of the forearm. Second layer

Superficial flexor muscle (flexor digitorum suprifi-cialis) starts from the internal epicondyle of the humerus, the coronoid process of the ulna and middle third ulna. The muscle continues into four tendons for the 2nd-5th fingers. The tendons pass under the flexor retinaculum in the carpal tunnel onto the hand and are attached to the palmar surface of the middle phalanges. At the level of the proximal phalanx, each tendon of this muscle diverges into two legs and passes through the gap the tendon of the deep flexor of the digitorum.

Function: bends the middle phalanges of the 2nd-5th fingers, takes part in flexion of the hand.

Anterior muscle group of the forearm. Third layer

Flexor digitorum profundus (flexor digitorum profundus) starts from the anterior surface of the ulna and the interosseous membrane, divides into four tendons, which pass through the carpal canal onto the hand, pierce the superficial flexor digitorum tendon at the level of the proximal phalanges and attach to the distal phalanges of the 2-5th fingers.

Function: flexes the distal phalanges of the 2nd-5th fingers, takes part in flexion of the hand.

Flexor pollicis muscle (t. flexor pollicis longus) starts from the interosseous membrane and the anterior surface of the radius. The tendon passes through the carpal tunnel and attaches to the base of the distal phalanx of the thumb.

Function: flexes the distal phalanx of the thumb, takes part in flexion of the hand.

Anterior muscle group of the forearm. Fourth layer

Pronator quadratus located in the lower third of the forearm, starting from the anterior surface of the ulna. Attaches to the anterior and lateral surface of the radius.

Function: pronates the forearm and hand.

Posterior muscle group of the forearm. Surface layer

Extensor carpi radialis (t. extensor carpi radialis longus) starts from the lateral epicondyle of the humerus and the lateral intermuscular septum of the shoulder. Going down, passes under long muscle, abductor pollicis, and extensor pollicis brevis, extensor retinaculum and is attached to the base of the 2nd metacarpal bone.

Function: extends the radial edge of the hand and takes part in flexing the forearm at the elbow joint.

Extensor carpi radialis brevis (extensor carpi radialis brevis) starts from the lateral epicondyle of the humerus. Attaches to the base of the 3rd metacarpal bone.

Function: extends the hand.

Extensor digitorum (extensor digitorum) starts from the lateral epicondyle of the humerus and the fascia of the forearm. The muscle belly passes into four tendons, which pass under the extensor retinaculum and are attached to the bases of the middle phalanges of the 2-5th fingers.

Function: extends fingers 2-5, participates in wrist extension.

Extensor of the little finger (t. extensor dfgiti minimi) begins next to the previous muscle. The tendon passes under the extensor retinaculum and is attached to the bases of the middle and distal phalanges of the little finger.

Function: extends the little finger.

Extensor carpi ulnaris (extensor carpi ulnaris) starts from the lateral epicondyle of the humerus and the fascia of the forearm. Attached to the base of the 5th metacarpal bone.

Function: extends the ulnar edge of the hand.

Posterior muscle group of the forearm. Deep layer

Supinator muscle (t. supinator) starts from the lateral epicondyle of the humerus and the crest of the muscle - the supinator of the ulna. Attaches to the outer surface of the upper third of the radius. Function: supinates the radius and hand.

Melon muscle, abductor pollicis longus (abductor pollicis longus), starts from the posterior surface of the radius and ulna, from the interosseous membrane. Attached to the base of the 1st metacarpal bone.

Function: abducts the 1st finger, participates in abduction of the hand. Extensor pollicis brevis (t. extensor pollicis brevis) begins next to the previous muscle from the interosseous membrane. Attaches to the base of the proximal phalanx of the thumb. Function: extends the thumb.

Extensor pollicis muscle (t. extensor pollicis longus) starts from the posterior surface of the ulna and the interosseous membrane of the forearm. Attaches to the base of the distal phalanx of the thumb, where it merges with the extensor brevis tendon. Function: extends the thumb.

Extensor index finger (extensor indicis) starts from the posterior surface of the ulna and the interosseous membrane of the forearm. It is attached to the proximal phalanx of the index finger, where it fuses with the extensor tendon of the fingers.

Function: extends the 2nd finger.

MUSCLES OF THE FOREARM

Each group is composed of superficial and deep layers. The superficial layer of the muscles of the anterior group originates in the region of the medial epicondyle of the shoulder, the same layer of the posterior group originates in the region of the lateral epicondyle. The deep layer of both groups in its main part no longer finds a place of attachment on the epicondyles, but originates on the bones of the forearm and on the interosseous membrane. The final attachments of the flexors and extensors of the hand are located at the bases of the metacarpal bones, and the same muscles going to the fingers are attached to the phalanges, with the exception of the long abductor pollicis muscle, which is attached to the first metacarpal bone.

FRONT GROUP

Surface layer consists of the following muscles.

1. M. pronator teres, round pronator, starts from the medial epicondyle of the humerus and tuberositas deltae and attaches to the lateral surface of the radius immediately above its middle.

Function. Pronates the forearm and participates in its flexion.

2. M. flexor carpi radialis, flexor carpi radialis, lies along the medial edge of the pronator teres. It starts from the medial epicondyle of the humerus and attaches to the base of the second metacarpal bone.

Function. Produces palmar flexion of the hand, and can also abduct the latter to the radial side in combination with other muscles.

3. M. palmaris longus, long palmaris muscle, lies medial from the previous one and starts from the medial epicondyle of the shoulder. Its short fusiform abdomen passes very high into a thin long tendon, which, on top of the retinaculum flexorum, passes into the palmar aponeurosis, aponeurosis palmaris. This muscle is often absent.

Function. Stretches the palmar aponeurosis and performs palmar flexion of the hand.

4. M. flexor carpi ulnaris, flexor carpi ulnaris, is located on the ulnar edge of the forearm, originating from the medial epicondyle of the shoulder, and is attached to the pisiform bone, which is a sesamoid for it, and further to the os hamatum (in the form of lig. pisohamatum) and the fifth metacarpal bone (in the form of lig. pisometacarpeum).

Function. Together with m. flexor carpi radialis produces palmar flexion of the hand, as well as ulnar adduction of the latter (together with the m. extensor carpi ulnaris).

5. M. flexor digitorum superficialis, superficial flexor of the fingers, lies deeper than the four muscles described. It starts from the medial epicondyle of the humerus, processus coronoideus of the ulna and the upper part of the radius. The muscle is divided into four long tendons, which descend from the forearm through the canalis carpalis to the palm, where they go to the palmar surface of the II-V fingers.

At the level of the body of the proximal phalanx, each of the tendons is divided into two legs, which, diverging, form a gap, hiatus tendineus, for the passage of the deep flexor tendon, with which they intersect (chiasma tendinum), and are attached to the palmar surface of the base of the middle phalanx (Fig. 85 ).

Function. Flexes the proximal and middle phalanx of the fingers (except for the thumb), as well as the entire hand.

Deep layer:

6. M. flexor pollicis longus, long flexor pollicis, starts from the anterior surface of the radius distal to the tuberositas radii and often from the medial epicondyle of the humerus. The long tendon passes under the retinaculum flexorum on the palm and is directed in the groove between both heads of the m. flexor pollicis brevis to the base of the second phalanx of the thumb.

Function. Flexes the nail phalanx of the thumb, as well as the hand.

7. M. flexor digitorum profundus, deep flexor of the digitorum. It originates from the ulna and the interosseous membrane. Its four tendons, extending from the body of the muscle in the middle of the forearm, pass through the canalis carpalis into the palm, lying under the tendons of the superficial flexor, and then go to the II-V fingers, and each of these tendons penetrates the hiatus tendineus between the legs of the tendon m. flexor digitorum superficialis, forming a cross with it, and is attached to the distal phalanx.

Function. Flexes the middle and distal phalanges of the II-V fingers, and also participates in flexion of the hand.

8. M. pronator quadratus, square pronator(Fig. 86), is a flat quadrangular muscle located directly on both bones of the forearm and on the interosseous membrane, immediately above the carpal joints. Starting from the palmar surface of the ulna, it is attached to the palmar side of the radius.

Function. It is the main pronator of the forearm, and the round one is auxiliary (Fig. 87).

REAR GROUP

Surface layer posterior muscles can be divided into two secondary groups: radial and ulnar. The first of them occupies the anterolateral surface of the forearm, and the second lies on its posterior side.

Ray group of the surface layer (Fig. 88; Fig. 89).

1. M. brachioradialis, brachioradialis muscle, lies in front of the forearm, along its lateral edge. This muscle starts from the lateral edge of the humerus, located between m. brachialis and m. triceps. Then its belly descends in front of the radius and in the middle of the forearm it passes into a long tendon, which is attached to the radius above the styloid process. Medially the muscle borders m. pronator teres and m. flexor carpi radialis.

Function. Flexes the forearm at the elbow joint and places the radius in a position intermediate between pronation and supination (this position is usually taken by the forearm and hand with freely lowered arms).

2. M. extensor carpi radialis longus, long extensor carpi radialis, is located lateral and posterior to the previous muscle and originates from the lateral edge and lateral epicondyle of the shoulder. In the middle of the forearm, the muscle turns into a tendon, which runs along the lateral surface of the radius, then fits under the retinaculum extensorum and attaches to the dorsal surface of the base of the second metacarpal bone.

Function. Flexes the forearm, performs dorsal flexion of the hand, as well as abduction (to the radial side) (the latter together with the m. flexor, carpi radialis).

3. M. extensor carpi radialis brevis, short extensor carpi radialis, lies posterior to the long extensor carpi radialis, starting from the lateral epicondyle of the humerus, goes along with the tendon m. extensor carpi radialis longus, and both of them intersect with m in the distal third of the forearm. abductor pollicis longus and m. extensor pollicis brevis, and in the area of the hand - with the tendon of the long extensor pollicis. Next, they pass through the common (second) fibrous canal under the retinaculum extensorum, after which the tendon of the short extensor carpi radialis is attached to the dorsal surface of the base of the third metacarpal bone. In this place there is a small synovial bursa underneath.

Function. Same as the extensor carpi radialis longus.

Ulnar group of the superficial layer.

4. M. extensor digitorum, extensor digitorum, lies completely on the back surface of the forearm, originating together with m. extensor carpi radialis brevis from epicondylus lateralis. In the middle of the forearm, the muscle divides into four bellies, each of which gives rise to a long tendon.

The tendons descend to the back of the hand, pass under the retinaculum extensorum through the fourth of the canals located here, and then diverge to the four fingers (II-V). On the back of the hand, near the metacarpophalangeal joints, the tendons are connected to each other by oblique fibrous bridges, connexus intertendineus, as a result of which extension of the two middle fingers is only possible together; the index finger and partly the little finger retain independence due to the existence of their own extensors. Each of the common extensor tendons on the dorsum of the corresponding finger passes into a triangular tendon extension, divided into three bundles, of which the middle one is attached to the base of the middle phalanx, and the two lateral ones are attached to the base of the distal phalanx.

Function. Extends fingers II-V and performs dorsal flexion of the hand.

5. M. extensor digiti minimi, extensor of the little finger, is separated from the common extensor digitorum on its ulnar side. Its long tendon passes through the fifth canal under the retinaculum extensorum on the back of the hand to the little finger and connects with the common extensor tendon going to this finger.

The function is clear from the name.

6. M. extensor carpi ulnaris, extensor carpi ulnaris, adjacent with its lateral edge to the common extensor and extensor of the little finger, begins together with these muscles from the lateral epicondyle of the shoulder, as well as from the posterior edge of the ulna. The tendon of the muscle passes through the sixth tendon canal under the retinaculum extensorum and is attached to the base of the fifth metacarpal bone.

Function. Dorsiflexes the hand and brings it to the ulnar side, the latter together with m. flexor carpi ulnaris.

Deep layer:

7. M. supinator, supinator, located in the upper outer part of the forearm; it is covered with m. brachioradialis and both radial extensors of the hand. Starting from the lateral epicondyle of the shoulder, lig. collateral radiale of the elbow joint and from the upper end of the ulna, it covers the proximal end of the radius above and below the tuberositas radii.

Function. Clean arch support - forearms.

8 and 9. M. abductor pollicis longus, long, abductor pollicis, muscle, m. extensor pollicis brevis, short extensor pollicis, begin near the posterior surface of the radius, from the interosseous membrane and partly from the ulna, the first muscle is higher than the second. From here, lying together, they go distally and laterally they emerge from under the radial edge of the common extensor digitorum and, passing through the first canal under the retinaculum extensorum, go to the thumb, where the tendon m. abductor pollicis longus is attached partly to the base of the first metacarpal bone, partly to the tendon origin of m. abductor pollicis brevis, and the tendon m. extensor pollicis brevis - to the base of the proximal phalanx of the thumb.

Function. M. abductor pollicis longus abducts the thumb and produces radial abduction of the hand, m. extensor pollicis brevis extends the proximal phalanx of the thumb.

10. M. extensor pollicis longus, long extensor pollicis, starting from the middle third of the posterior surface of the ulna, emerges with its tendon from under the common extensor digitorum below the previous two muscles, crosses obliquely the tendons of both radial extensors of the hand, passes under the retinaculum extensorum in the third canal and then goes to the back of the thumb, where it attaches to the base of his second phalanx. On the radial side of the wrist joint, between the tendons of m. extensor pollicis longus on one side and mm. extensor pollicis brevis and abductor pollicis longus on the other, a depression is formed called the anatomical snuffbox.

Function. Extends the thumb, pulling it to the back.

11. M. extensor indicis, extensor of the index finger, originates from the distal third of the posterior surface of the ulna. Its tendon passes together with the tendons of the common extensor digitorum through the fourth canal under the retinaculum extensorum and joins the ulnar side of the common extensor tendon going to index finger, turning into a dorsal tendon stretch of this finger.

The function corresponds to the name.