MUSCLES OF THE FOREARM AND MANUS A Extensor

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MUSCLES OF THE FOREARM AND MANUS

MUSCLES OF THE FOREARM AND MANUS

A. Extensor Division 1. Extensor carpi radialis : Location : This is the largest

A. Extensor Division 1. Extensor carpi radialis : Location : This is the largest muscle of the extensor division, and lies on the cranial (dorsal) surface of the radius. Origin. —(1) The lateral epicondyloid crest of the humerus; (2) the coronoid fossa. Insertion. —Metacarpal tuberosity Action. —To extend and fix the carpal joint and to flex the elbow joint. Blood-supply. —Transverse cubital artery. Nerve-supply. —Radial nerve

2. common digital extensor: Location : This muscle lies lateral to the foregoing, which

2. common digital extensor: Location : This muscle lies lateral to the foregoing, which it resembles in general form, although less bulky. Origin. —(1) The cranial aspect of the distal extremity of the humerus, just lateral to the coronoid fossa; (2) the lateral tuberosity on the proximal extremity of the radius, the lateral ligament of the elbow, and the lateral border of the radius at the junction of its proximal and middle thirds; (3) the lateral surface of the shaft of the ulna; (4) the fascia of the forearm. Insertion. —(1) The extensor process of the third phalanx; (2) the dorsal surface of the proximal extremities of the first and second phalanges. Action. —To extend the digital and carpal joints, and to flex the elbow joint. Blood supply : radial , cranial interosseous and Transverse cubital arteries Nerve supply : Radial nerve

3. Lateral digital extensor : Location : This muscle is much smaller than the

3. Lateral digital extensor : Location : This muscle is much smaller than the preceding, behind which it is situated. Origin. —The lateral tuberosity of the radius and the lateral ligament of the elbow joint, the shaft of the ulna, the lateral border of the radius, and the intermuscular septum. Insertion. —An eminence on the dorsal of the proximal extremity of the first phalanx. Action. —To extend the digit and carpus. Blood-supply. —Interosseous artery. Nerve-supply. —Radial nerve

4. abductor digit (Extensor carpi obliquus) : Location : This is a small muscle

4. abductor digit (Extensor carpi obliquus) : Location : This is a small muscle which curves obliquely over the distal half of the radius and the carpus. Origin. —The lateral border and adjacent part of the cranial surface of the radius. Insertion. —The head of the medial (second) metacarpal bone. Action. —To extend the carpal joint. Blood-supply. —Interosseous and transverse cubital arteries. Nerve-supply. —Radial nerve

B. Flexor Division 1. Flexor carpi radialis: Location : This muscle lies on the

B. Flexor Division 1. Flexor carpi radialis: Location : This muscle lies on the medial surface of the forearm, immediately behind the medial border of the radius. Origin. —The medial epicondyle of the humerus, below and behind the medial ligament. Insertion. —The proximal end of the medial (second) metacarpal bone. Action. —To flex the carpal joint and to extend the elbow. Blood-supply. —Median artery. Nerve-supply. —Median nerve

2. flexor carpi ulnaris : Location : This muscle lies on the medial and

2. flexor carpi ulnaris : Location : This muscle lies on the medial and caudal aspect of the forearm partly under, partly behind, the preceding muscle. It arises by two heads—humeral and ulnar. Origin. (1) The medial epicondyle of the humerus just behind the preceding muscle. (2) the medial surface and caudal border of the olecranon. Insertion. —The proximal edge of the accessory carpal bone. Action. —To flex the carpal joint, and to extend the elbow. Blood-supply. — collateral ulnar and median arteries. Nerve-supply. —Ulnar and median nerves.

3. ulnaris lateralis; lateralis Location : This muscle lies on the lateral face of

3. ulnaris lateralis; lateralis Location : This muscle lies on the lateral face of the forearm, behind the lateral extensor of the digit. Origin. —The lateral epicondyle of the humerus, behind and below the lateral ligament. Insertion. —(1) The lateral surface and proximal edge of the accessory carpal bone; (2) the proximal extremity of the fourth metacarpal bone. Action. —To flex the carpal joint and to extend the elbow. Blood-supply. —Interosseous, collateral ulnar, and median arteries. Nerve-supply. —Radial nerve.

4. Superficial digital flexor : Location : This muscle is situated in the middle

4. Superficial digital flexor : Location : This muscle is situated in the middle of the flexor group , between the flexor carpi ulnaris and flexor digitorum. Origin. —(1) The medial epicondyle of the humerus (2) a ridge on the caudal surface of the radius, distal to its middle and near the medial border. Insertion. —(1) The eminences on the proximal extremity of the second phalanx palmar the lateral ligaments; (2) the distal extremity of the first phalanx, also palmar the lateral ligaments. Action. —To flex the digit and carpus, and to extend the elbow. Blood-supply. —Caudal radial artery. Nerve-supply. —Median nerve.

5. Deep digital flexor: Location : The fleshy part of this muscle lies on

5. Deep digital flexor: Location : The fleshy part of this muscle lies on the caudal surface of the radius, under cover of the preceding muscles. It is the largest muscle of the flexor group. Origin. —(1) The medial epicondyle of the humerus; (2) the medial surface of the olecranon; (3) the middle of the caudal surface of the radius and a small adjacent area of the ulna. Insertion. —The semilunar crest of the third phalanx, and the adjacent surface of the lateral cartilage. Action. —To flex the digit and carpus, and to extend the elbow. Blood-supply. —Caudal radial and ulnar arteries. Nerve-supply. —Median and ulnar nerves.

Metacarpal muscles : The five muscles of this group are either reduced to vestiges

Metacarpal muscles : The five muscles of this group are either reduced to vestiges or modified greatly in structure. 1, 2. Lumbricales (internus et externus). —These are two small muscles which lie on either side of the flexor tendons above the fetlock. Origin : They arise from the deep flexor tendon, Insertion : and are lost in the fibrous tissue which lies under the nodule of horn or ergot at the fetlock. Action : Their action is inappreciable. The size of these muscles is subject to much variation. Often very little muscular tissue can be found, but the small tendon is constantly present. Blood-supply. —Metacarpal arteries. Nerve-supply. —Median and ulnar nerves.

3, 4, 5. Interossei Muscles —These are three in number in the horse, Location

3, 4, 5. Interossei Muscles —These are three in number in the horse, Location : situated chiefly in the metacarpal groove. A- Two, the medial and lateral , are very small muscles, Origin : arises from the corresponding small metacarpal bone near its proximal extremity and is provided with a delicate tendon which Insertion : lost in the fascia at the fetlock. Action : They have no appreciable action. blood- and nerve-supply is the same as that of the preceding muscles. B- The interosseus medius is so much modified that it is usually termed the suspensory, or superior sesamoidean ligament. It contains little muscular tissue, being transformed very largely into a strong tendinous band, bifurcate below and having for its chief function the supporting of the fetlock.