Forearm Muscles : Attachment, Nerve Supply & Action

Forearm Muscles: The forearm is the region of the upper limb between the elbow and the wrist. The forearm muscles divided into-

  • Anterior compartment
  • Posterior compartment

Anterior Compartment

Anterior compartment of the forearm muscles divided into superficial & deep muscles.

Superficial muscles:

  • Pronator teres
  • Palmaris longus
  • Flexor carpi radialis
  • Flexor carpi ulnaris
  • Flexor digitorum superficialis

Pronator teres: It has two head.

  • Origin:
    • Humeral head: medial epicondyle of humerus
    • Ulnar head: Medial border of coronoid process of ulna
  • Insertion:
    • Middle of the lateral aspect of the shaft of the radius.
  • Action:
    • Pronation of forearm

Flexor carpi ulnaris:

  • Origin: It has two head.
    • Humeral head: Medial epicondyle of humerus
    • Ulnar head: Medial aspect of olecranon process of ulna and posterior border of ulna
  • Insertion:
    • Pisiform bone, the hook of hamate and base of the 5th metacarpal bone
  • Action:
    • Flexes and abducts hand at wrist joint

Palmaris longus:

  • Insertion:
    • Flexor retinaculum and palmar aponeurosis
  • Action:
    • Flexes wrist joint

Flexor carpi radialis:

  • Insertion:
    • Bases of 2nd and 3rd metacarpal bones
  • Action
    • Flexes and abducts hand at wrist joint

 

forearm muscles

Flexor digitorum superficialis

  • Origin:
    • All superficial muscles are arises from the medial epicondyle of humerus but they are inserted into the different part except
  • Insertion:
    • The middle phalanx of 2nd to 5th digits ( four fingers)
  • Action:
    • Flexes middle phalanx of fingers and assists in flexing proximal phalanx and wrist joint
  • Nerve supply:
    • All muscles are supplied by median nerve except flexor carpi ulnaris supplied by the ulnar nerve

Deep muscles:

  • Flexor digitorum profundus
  • Flexor pollicis longus
  • Pronator quadratus

Flexor digitorum profundus( hybrid muscle):

  • Origin:
    • Upper three-fourths of the anterior and medial surface of the shaft of ulna
    • Upper three-fourths of the posterior border of ulna
    • Medial surface of the olecranon and coronoid processes of the ulna
  • Insertion:
    • Flexor retinaculum( medial 4 digits)
  • Nerve supply:
    • Medial half by the ulnar nerve
    • Lateral half by anterior interosseous nerve(c8 , t1)
  • Action:
    • Flexor of distal phalanges after the flexor digitorum superficialis has flexed the middle phalanges.

Flexor pollicis longus:

  • Origin:
    • Upper three- fourths of the anterior surface of the shaft of the radius
  • Insertion:
    • Palmar surface of the distal phalanx of the thumb
  • Nerve supply:
    • Anterior interosseous nerve
  • Action:
    • Flexes the distal phalanx of the thumb

forearm deep anterior muscles

Pronator quadratus:

  • Origin:
    • The oblique ridge on the lower one-fourth of the anterior surface of the shaft of ulna
  • Insertion:
    • Lower one-fourth of the anterior surface and the anterior border of the radius, Ulnar notch
  • Nerve supply:
    • Anterior interosseous nerve
  • Action:
    • Pronate the forearm

Posterior Compartment

Posterior compartment of the forearm muscles divided into superficial & deep muscles.
Superficial muscles:

  • Anconeus
  • Brachioradialis
  • Extensor carpi radialis longus
  • Extensor carpi radialis brevis
  • Extensor digitorum
  • Extensor digiti minimi
  • Extensor carpi ulnaris

Superficial muscles:

  • Origin:
    • All are arises from the lateral epicondyle of the humerus.

Anconeus:

  • Insertion:
    • The lateral surface of olecranon process of ulna
  • Nerve supply:
    • Radial nerve
  • Action:
    • Extends elbow joint

Brachioradialis:

  • Insertion:
    • The base of styloid process of radius
  • Nerve supply:
    • Radial nerve
  • Action:
    • Flexes forearm at the elbow joint and rotates forearm to the midprone position from supine or prone positions

Extensor carpi radialis longus:

  • Insertion:
    • The posterior surface of the base of the 2nd metacarpal bone
  • Nerve supply:
    • Radial nerve
  • Action:
    • Extends and abducts hand at wrist jointposterior forearm muscles

Extensor carpi radialis brevis:

  • Insertion:
    • The posterior surface of the base of the third metacarpal bone
  • Nerve supply:
    • Deep branch of the radial nerve
  • Action:
    • Extends and abducts hand at wrist joint

Extensor digitorum:

  • Insertion:
    • Bases of middle phalanges of the 2nd-5th digits
  • Nerve supply:
    • Deep branch of the radial nerve
  • Action:
    • Extends fingers of the hand

Extensor digiti minimi:

  • Insertion:
    • Extensor expansion of little finger
  • Nerve supply:
    • Deep branch of the radial nerve
  • Action:
    • Extends metacarpophalangeal joint of the little finger

Extensor carpi ulnaris:

  • Insertion:
    • The base of the fifth metacarpal bone
  • Nerve supply:
    • Deep branch of the radial nerve
  • Action:
    • Extends and adducts hand at wrist joint

Deep muscles:

  • Supinator
  • Abductor pollicis longus
  • Abductor pollicis brevis
  • Extensor pollicis longus
  • Extensor indicis

Supinator:

  • Origin:
    • Lateral epicondyle of humerus
  • Insertion:
    • Neck and shaft of upper 1/3rd of radius
  • Nerve supply:
    • Deep branch of the radial nerve
  • Action:
    • Supination of the forearm when the elbow is extended

Abductor pollicis longus:

  • Origin:
    • The posterior surface of the shaft of radius and ulna
  • Insertion:
    • The base of the first metacarpal bone
  • Nerve supply:
    • Deep branch of the radial nerve
  • Action:
    • Abducts and extends the thumb

Deep Posterior Compartment of forearm muscles

Extensor pollicis brevis:

  • Origin:
    • The posterior surface of the shaft radius
  • Insertion:
    • The base of proximal phalanx of the thumb
  • Nerve supply:
    • Deep branch of the radial nerve
  • Action:
    • Extends metacarpophalangeal joint of the thumb

Extensor pollicis brevis:

  • Origin:
    • The posterior surface of the shaft of ulna
  • Insertion:
    • The base of distal phalanx of the thumb
  • Nerve supply:
    • Deep branch of the radial nerve
  • Action:
    • Extends distal phalanx of the thumb

Common Elbow Conditions: Tennis Elbow, Golfers Elbow & Cubital Tunnel  Syndrome.

Forearm Movements

Supination of forearm muscles-Supinator.
Pronation of forearm muscles-Pronator teres & Pronator quadratus.


Elbow flexor muscles-Biceps brachii, Brachialis, Brachioradialis, Pronator teres.
Elbow extensor muscles-Triceps brachii & Anconeus

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