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 are the cranial nerves. But the hardest part of myology in normal anatomy- forearm, that's for sure. The forearm strikes students in lectures, sometimes there is simply no idea how it is all possible to learn.

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

First of all, let's remember that the hand must be considered only in a physiological position. We will have ahead a large number of schemes, at your seminars you will also answer on tablets and preparations - and so, everywhere, absolutely everywhere, the hands are in the correct physiological position. That is inside palms forward and nails back. As in 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 up reverse grip- the biceps work, and he is in front. When we bring our palm closer to the shoulder, bending the arm at the elbow joint, we are using the biceps. It’s the same with the forearm - the flexor muscles are in front, let’s start with them

MUSCLES OF THE FOREARM, FRONT GROUP:

surface layer.

1. Our main landmark here - powerful, large brachioradialis muscle(musculus brachioradialis). Her special features: she is very wide, powerful, against the background of other muscles. It occupies the most lateral position (if the hand is located physiologically).

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

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

2. Round pronator(musculus pronator teres). Using our first landmark, we can easily identify a round pronator (in what place is the round truth, a question for ancient anatomists). It is he who, with the brachioradialis, the widest and most lateral muscle, forms the letter Y. It is 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 rather wide and short). Attaches to the center of the radius from the lateral side.
Function: flexion of the arm at the elbow joint, and also pronates the forearm.

By the way, there is great way remember what suppination 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 hand over, the soup spills and pronation occurs.

3. Remember this Y, which is formed by our main landmark - the brachioradialis muscle (the most lateral, very large) and the round pronator, which is adjacent to it at an acute angle. But it fits very tightly to the round pronator radial flexor wrists(musculus flexor carpi radialis). It doesn't look very lateral, of course, but we'll have another flexor with respect to which the flexor carpi radialis will be really lateral.

Location: originates from the medial epicondyle of the humerus, inserts on the second metacarpal.
Function: As the name implies, this muscle flexes the wrist.

4. We are talking about this particular muscle - flexor carpi ulnaris(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 medial epicondyle of the humerus already familiar to us, as well as from rear surface ulna (the muscle has two heads). Attached to the hamate bone.
Function: flex brush

5. So, we have two flexors - radial and ulnar. And between them will pass long palmar muscle (Musculus palmaris longus). I specifically chose to leave the flexor radius and ulnar flexors tinted because they are excellent reference points for finding the longus volar muscle. I marked the long palmar muscle itself with a red dotted line.

An important feature of the long palmar muscle is that it is woven into a wide palmar aponeurosis. You can find the long palmar muscle on the preparation by first finding the aponeurosis itself, and then, looking a little more proximal, the extended tendon of the long palmar muscle.

Location: starts from the medial epicondyle of the humerus, is attached, as we have already found out, to the wide palmar aponeurosis.
Function: bends the brush. Do not confuse, this muscle flexes 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 a round pronator - 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) is a long palmar muscle with a very characteristic direction directly to the center of the palm, to the palmar aponeurosis.
Titles. Pronator - pronates, wrist flexors, oddly enough, flex the wrists. At three muscles out of five, the function is in the name.
Location pattern. All muscles, except for the brachioradialis, originate from the medal epicondyle of the humerus.

lexical minimum.

The traditional list of Latin muscle names that you should show on tablets without any problems, 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, and some of them bend and unbend the entire brush as a whole, while others - fingers. In addition, there are also pronators and supinators that produce the corresponding movements of the radius. By position, all these muscles fall into two groups: the anterior, which includes flexors and pronators, and the posterior, consisting of extensors and supinators.

Each group is composed of superficial and deep layers. The surface 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 - 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 terminal attachments of the flexors and extensors of the hand are 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 thumb muscle, which is attached to the I metacarpal bone.

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 pass into long tendons, as a result of which the forearm has the shape of a cone, flattened from front to back.

Anterior forearm muscles

Superficial layer of muscles of the forearm consists of the following muscles.

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

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

2. M. flexor carpi radialis, radial flexor of the wrist lies along the medial edge of the round pronator. It starts from the medial epicondyle of the shoulder and is attached to the base of the II metacarpal bone.

Function. Produces flexion of the hand, and can also take the latter to the radial side in combination with other muscles. (Inn. CVI-VII N. medianus.)

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

Function. Stretches the palmar aponeurosis and flexes the hand. (Inn. СVII - ThI N. medianus.)

4. M. flexor carpi ulndris, ulnar flexor of the wrist, 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 sesamoid for it, and then to the os hamatum (in the form of lig. pisohamatum) and the V metacarpal bone (in the form of lig. pisometacarpeum).

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

5. M. flexor digitorum superflcialis, superficial finger flexor, lies deeper than the described four muscles. It starts from the medial epicondyle of the humerus, the processus coronoideus of the ulna and the upper part of the radius.
The muscle divides 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, to pass 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 (with the exception of 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 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 goes in the groove between both heads 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 brush. (Inn. N. medianus.)

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

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

8. M. pronator quadratus, square pronator, represents 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 round one is auxiliary. (Inn. CIV - ThI N. medianus.)

Video lesson of the anatomy of the muscles of the forearm

The anatomy of the muscles of the forearm on the preparation of the corpse is disassembled

The muscles of the forearm are divided into posterior and anterior groups, in each of which the superficial and deep layers are distinguished.

front group

Surface layer

Round pronator(m. pronator teres) (Fig. 111, 115, 116, 117, 125) pronates the forearm (rotates it forward and inward in such a way that the palm turns backward (down), and the thumb inward to the median plane of the body) and participates in his bend. thick 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 shoulder fascia, and the small, ulnar, head (caput ulnare) starts from the coronoid process of the tuberosity of the ulna. Both heads, connecting, form a flattened abdomen. The place of attachment 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 in such a way that the palm turns forward (up), and the thumb is outward from the median plane of the body) of the radius. The muscle has a spindle 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.

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

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

A characteristic feature of the muscle structure is a short spindle-shaped abdomen and a long tendon. It begins on the medial epicondyle of the humerus and fascia of the forearm, medially from the radial flexor of the wrist, and is attached to the palmar aponeurosis (aponeurosis palmaris).

Elbow flexor of the hand(m. flexor capiti ulnaris) (Fig. 90, 115, 116, 118, 121, 125) bends the brush and takes part in its adduction. It is characterized by a long abdomen, thick tendon and two heads. The brachial head has the medial epicondyle of the humerus and the fascia of the forearm as the starting point, and the ulnar head has the olecranon and the upper two-thirds of the ulna. Both heads are attached to the pisiform bone, part of the bundles is attached to the hamate and V metacarpal bones.

Superficial finger flexor(m. flexor digitorum superficialis) (Fig. 115, 116, 120, 125) bends the middle phalanges of the II-V fingers. This broad muscle covered by the radial flexor of the wrist and the long palmar muscle and consists of two heads. The humeral head (caput humeroulnare) starts from the medial epicondyle of the humerus and ulna, the radial head (caput radiale) - from the proximal radius. The heads form a single abdomen with four tendons that pass to the hand and are each attached with two legs to the base of the middle phalanges of the II-V fingers of the hand.

deep layer

Long flexor thumb(m. flexor pollicis longus) (Fig. 115, 116, 120) flexes the distal phalanx of the I (thumb) finger. A long, flat, unipennate muscle, the point of origin has 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. Attaches at the base of the distal phalanx of the thumb.

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

Square pronator(m. pronator quadratus) (Fig. 116, 117, 120, 121) rotates the forearm inward (pronates). The muscle is a thin quadrangular plate located in the region of the distal ends of the bones of the forearm. It originates on the medial edge of the body of the ulna and inserts on 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) flexes the forearm at the elbow joint, extends the hand and takes part in its abduction. The muscle has a fusiform shape and is distinguished by a narrow tendon, significantly exceeding the length of the abdomen. Top part 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 shoulder fascia, and the attachment point is on the dorsum of the base of the second metacarpal bone.

extensor carpi radialis brevis(m. extensor carpi radialis brevis) (Fig. 90, 122, 123, 125) unbends the brush, slightly retracting it. This muscle is slightly covered by the long radial extensor of the wrist, starts from the lateral epicondyle of the humerus and the fascia of the forearm, and is attached to the dorsal surface of the base of the III metacarpal bone.

Rice. 115. Shoulder muscles and shoulder girdle front view 1 - biceps muscle of the shoulder; 2 - shoulder muscle; 4 - aponeurosis of the biceps muscle of the shoulder; 5 - round pronator; 6 - brachioradialis muscle; 7 - radial flexor brush; 8 - elbow flexor brush; 9 - long palmar muscle; 10 - superficial flexor of the fingers; 11 - long flexor of the thumb; 12 - short palmar muscle; 13 - palmar aponeurosis
Rice. 116. Forearm muscles front view 1 - shoulder muscle; 2 - supinator; 3 - tendon of the biceps muscle of the shoulder; 4 - long radial extensor of the wrist; 5 - deep flexor of the fingers; 6 - brachioradialis muscle; 7 - long flexor of the thumb; 8 - round pronator; 9 - elbow flexor brush; 10 - square pronator; 11 - a muscle that opposes the thumb of the hand; 12 - the muscle leading the little finger; 13 - short flexor of the thumb; 14 - tendons of the deep flexor of the fingers; 15 - tendon of the long flexor of the thumb; 16 - tendons of the superficial flexor of the fingers
Rice. 117. Forearm muscles front view 1 - round pronator; 2 - tendon of the biceps muscle of the shoulder; 3 - supinator; 4 - interosseous membrane; 5 - square pronator
Rice. 118. Muscles of the forearm, rear view 1 - brachioradialis muscle; 2 — triceps shoulder 3 - long radial extensor of the wrist; 4 - ulnar muscle; 5 - elbow flexor brush; 6 - extensor of the fingers; 7 - ulnar extensor of the wrist; 8 - extensor of the little finger; 9 - a long muscle that removes the thumb of the hand; 10 - short extensor of the thumb; 11 - extensor retinaculum; 12 — extensor longus thumb of the hand; 13 - extensor tendons of the fingers
Rice. 119. Muscles of the forearm, rear view 1 - supinator; 2 - deep flexor of the fingers; 3 - a long muscle that removes the thumb of the hand; 4 - long extensor of the thumb; 5 - short extensor of the thumb; 6 - extensor of the index finger; 7 - extensor retinaculum; 8 - extensor tendons of the fingers

Finger extensor(m. extensor digitorum) (Fig. 90, 118, 119, 122, 123, 125) extends the fingers and takes part in the extension of the hand. The abdomen of the muscle has a fusiform shape, the direction of the bundles is characterized by a two-pinnate shape. Its point of origin is located on the lateral epicondyle of the humerus and the fascia of the forearm. In the middle of its length, the abdomen passes into four tendons, which on the back of the hand pass into tendon extensions, and those with their middle part 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.

Little finger extensor(m. extensor digiti minimi) (Fig. 90, 118, 122, 123) unbends the little finger. A small fusiform muscle that originates on the lateral epicondyle of the humerus and inserts at the base of the distal phalanx of the fifth finger (little finger).

Elbow extensor of the wrist(m. extensor capiti ulnaris) (Fig. 90, 118, 122, 123, 125) unbends the brush and takes it to the elbow side. The muscle has a long fusiform abdomen, begins on the lateral epicondyle of the humerus and fascia of the forearm, and is attached to the base of the dorsal surface of the fifth metacarpal bone.

deep layer

Arch support(m. supinator) (Fig. 116, 117, 119, 125) rotates the forearm outwards (supinates) and takes part in the extension of the arm in the elbow joint. The muscle has the shape of a thin rhomboid 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 place of attachment of the arch support is located on the lateral, anterior and posterior sides of the upper third of the radius.

Long muscle that abducts the thumb(m. abductor pollicis longus) (Fig. 90, 118, 119, 123, 125), abducts the thumb and takes part in the abduction of the brush. The muscle is partially covered by the extensor of the fingers and the short radial extensor of the wrist, has a flat bipennate abdomen, turning into a thin long tendon. It originates on the posterior surface of the ulna and radius and inserts at the base of the first metacarpal.

Short extensor thumb(m. extensor pollicis brevis) (Fig. 90, 118, 119, 122, 123) abducts the thumb and unbends its proximal phalanx. The point of 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 basis of the proximal phalanx of the thumb and the capsule of the first metacarpophalangeal joint.

Long extensor thumb(m. extensor pollicis longus) (Fig. 118, 119, 123, 125) unbends the thumb, partly retracting it. The muscle has a spindle-shaped abdomen and a long tendon. The starting point is located on the posterior surface of the body of the ulna and the interosseous membrane, the attachment point is at the base of the distal phalanx of the thumb.

Index finger extensor(m. extensor indicis) (Fig. 119, 123, 125) unbends the index finger. This muscle sometimes missing. It is covered by the extensor of the fingers, has a narrow, long, spindle-shaped abdomen. It starts on the posterior surface of the body of the ulna and the interosseous membrane, and is attached to the dorsum of the middle and distal phalanges of the index finger.

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

Anterior group of muscles of the forearm. First layer

Shoulder muscle (t. brachioradialis) located on the lateral edge of the forearm, starts from the outer epicondyle of the humerus. Attached to the styloid process of the radius.

Function: flexes the forearm, rotates the radius.

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

Function: pronates the hand and flexes the forearm.

Radial wrist flexor (t. flexor carpi radialis) starts from the internal epicondyle of the humerus, passes into the tendon, which passes under the flexor retinaculum in the groove of the trapezoid bone and is attached to the base of the 2nd metacarpal bone.

Function: flexes the radial edge of the hand, takes part in the 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 attaches to the palmar aponeurosis.

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

Elbow flexor of the wrist (t. flexor carpi ulnaris) starts from the inner epicondyle of the humerus, the fascia of the forearm (humeral head) and from the olecranon, the posterior edge of the ulna (ulnar head). Attaches to the pisiform bone.

Function: flexes the ulnar edge of the hand and somewhat supinates it.

Anterior group of muscles of the forearm. Second layer

Superficial flexor of the paws (t. flexor digitorum suprifi-cialis) originates 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 to the hand and insert on 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 the tendon of the deep flexor of the fingers through the gap.

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

Anterior group of muscles of the forearm. third layer

Deep finger flexor (t. flexor digitorum profundus) starts from the anterior surface of the ulna and the interosseous membrane, is divided into four tendons, which pass in the carpal tunnel to the hand, pierce at the level of the proximal phalanges of the tendon of the superficial flexor of the fingers and attach to the distal phalanges of the 2nd-5th fingers.

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

D, flexor thumb (t. flexor pollicis longus) originates from the interosseous membrane and the anterior surface of the radius. The tendon passes through the carpal tunnel and inserts at the base of the distal phalanx of the thumb.

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

Anterior group of muscles of the forearm. fourth layer

Square pronator (t. pronator quadratus) located in the lower third of the forearm, starts from the anterior surface of the ulna. Attached to the anterior and lateral surface of the radius.

Function: penetrates the forearm and hand.

Posterior muscle group of the forearm. Surface layer

D, extensor carpi radialis (m. extensor carpi radialis longus) originates from the lateral epicondyle of the humerus and the lateral intermuscular septum of the shoulder. Going down, passing under long muscle abductor thumb, and a short extensor of the thumb, extensor retinaculum and is attached to the base of the 2nd metacarpal bone.

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

Short radial extensor of the wrist (t. extensor carpi radialis brevis) originates from the lateral epicondyle of the humerus. Attaches to the base of the 3rd metacarpal.

Function: unbends the brush.

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

Function: unbends the 2nd-5th fingers, participates in the extension of the hand.

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

Function: extends the little finger.

Elbow extensor of the wrist (t. extensor carpi ulnaris) originates from the lateral epicondyle of the humerus and the fascia of the forearm. Attaches to the base of the 5th metacarpal.

Function: unbends the ulnar edge of the hand.

Posterior muscle group of the forearm. deep layer

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

The melon muscle that abducts the thumb of the hand (i.e. 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.

Function: abducts the 1st finger, participates in the abduction of the hand. Short extensor thumb (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.

Dtnny extensor of the thumb (t. extensor pollicis longus) originates 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 of the hand.

Extensor of the index finger (t. extensor indicis) originates from the posterior surface of the ulna and the interosseous membrane of the forearm. Attaches 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 surface 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 - 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 terminal attachments of the flexors and extensors of the hand are 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 thumb muscle, which is attached to the I metacarpal bone.

FRONT GROUP

Surface layer consists of the following muscles.

1. M. pronator teres, round pronator, starts from the medial epicondyle of the shoulder and tuberositas dunae and is attached to the lateral surface of the radius immediately above its middle.

Function. Penetrates the forearm and participates in its flexion.

2. M. flexor carpi radialis, radial flexor of the hand, lies along the medial edge of the round pronator. It starts from the medial epicondyle of the shoulder and is attached to the base of the II metacarpal bone.

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

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

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

4. M. flexor carpi ulnaris, ulnar flexor of the hand, 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 sesamoid for it, and further to os hamatum (in the form of lig. pisohamatum) and V 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 m. extensor carpi ulnaris).

5. M. flexor digitorum superficialis, superficial finger flexor, lies deeper than the described four muscles. It starts from the medial epicondyle of the shoulder, the processus coronoideus of the ulna and the upper part of the beam. 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, to pass the tendon of the deep flexor, 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 (with the exception of the thumb), as well as the entire hand.

Deep Layer:

6. M. flexor pollicis longus, long flexor of the thumb, starts from the anterior surface of the radius distally from the tuberositas radii and often from the medial epicondyle of the shoulder. The long tendon passes under the retinaculum flexorum on the palm and goes in the groove between both heads 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 brush.

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

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

8. M. pronator quadratus, square pronator(Fig. 86), represents a flat quadrangular muscle located directly on both bones of the forearm and on the interosseous membrane, immediately above the 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 round one is auxiliary (Fig. 87).

REAR GROUP

Surface layer back 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 back side.

The 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 her abdomen descends in front of the radius and in the middle of the forearm passes into a long tendon, which is attached to the beam above the styloid process. Medially, the muscle borders on m. pronator teres and m. flexor carpi radialis.

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

2. M. extensor carpi radialis longus, long radial extensor of the hand, is located laterally and posteriorly from 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 that runs along the lateral surface of the radius, then fits under the retinaculum extensorum and is attached to the back surface of the base of the second metacarpal bone.

Function. Flexes the forearm, produces dorsiflexion of the hand, as well as its abduction (to the radial side) (the latter together with m. flexor, carpi radialis).

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

Function. Same as extensor carpi radialis longus.

Elbow group of the surface layer.

4. M. extensor digitorum, extensor of fingers, already 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 is divided into four bellies, each of which gives a long tendon.

The tendons descend to the rear of the hand, pass under the retinaculum extensorum through the fourth of the canals located here, and then diverge to four fingers (II-V). On the back of the hand, near the metacarpophalangeal joints, the tendons are interconnected 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 remain independent due to the existence of their own extensors. Each of the tendons of the common extensor on the back of the corresponding finger passes into a triangular tendon extension, which is divided into three bundles, of which the middle bundle is attached to the base of the middle phalanx, and the two lateral bundles to the base of the distal phalanx.

Function. Unbends fingers II-V and produces dorsal flexion of the hand.

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

The function is visible from the name.

6. M. extensor carpi ulnaris, ulnar extensor of the hand, 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. Makes the back flexion of the hand and bringing it to the elbow side, the latter together with m. flexor carpi ulnaris.

Deep Layer:

7. M. 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. Pure supinator - forearms.

8 and 9. M. abductor pollicis longus, long, abductor thumb, muscle, m. extensor pollicis brevis, a short extensor of the thumb, starts 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 they, lying together, go distally and to the lateral side come out from under the radial edge of the common extensor of the fingers and, having passed through the first channel under the retinaculum extensorum, go to the thumb, where the tendon m. abductor pollicis longus is attached partly to the base of the I metacarpal bone, partly to the tendon beginning m. abductor pollicis brevis, and 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 of the thumb, starting from the middle third of the posterior surface of the ulna, comes out with its tendon from under the common extensor of the fingers below the previous two muscles, crosses obliquely the tendons of both radial extensor brushes, passes under the retinaculum extensorum in the third canal and then goes to the rear of the thumb, where it is attached to the base of its second phalanx. On the radial side of the wrist joint, between the tendons m. extensor pollicis longus on one side and mm. extensor pollicis brevis and abductor pollicis longus, on the other hand, form a depression called the anatomical snuffbox.

Function. Unbends 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 along with the tendons of the common extensor of the fingers through the fourth canal under the retinaculum extensorum and joins the ulnar side of the tendon of the common extensor going to index finger, passing into the dorsal tendon stretch of this finger.

The function matches the name.