Forearm Muscles Anatomy

• The content is about the anatomy of the forearm muscles, specifically focusing on the superficial flexor group, the superficial extensor group, and the deep extensor group.
• It also covers the radial and ulnar arteries of the forearm.
• The information is presented by Professor Dr. Youssef Hussein.

Superficial Flexor Group

• These muscles are arranged from lateral to medial.
• The flexor digitorum superficialis is intermediate between the superficial and deep groups.
• Origin: Common flexor origin (mostly) from the front of the medial epicondyle of the humerus.
• Nerve Supply: Median nerve, except flexor carpi ulnaris, which is supplied by the ulnar nerve.
• Insertion and Action: Indicated by the name of the muscles.
• All muscles of pronation and supination insert into the radius.
• The muscles included in this group are Pronator Teres, Flexor Carpi Radialis, Palmaris Longus, Flexor Digitorum Superficialis, and Flexor Carpi Ulnaris.

Pronator Teres

• Origin: Two heads of origin
• Humeral (Superficial) head: Common flexor origin and lower part of the medial supracondylar ridge of the humerus.
• Ulnar (Deep) head: From the medial border of the coronoid process of the ulna.
• Insertion: An impression on the middle of the lateral surface of the radius.
• Nerve Supply: Median nerve (before piercing the muscle).
• Actions:
• Pronation of forearm (at radioulnar joints).
• Flexion of the elbow joint.

Flexor Carpi Radialis

• Origin: Common flexor origin.
• Insertion: Palmar surface of the base of the 2nd & 3rd metacarpal bones.
• Nerve supply: Median nerve.
• Actions:
• Flexion of the wrist joint.
• Abduction of the hand at the wrist joint.

Palmaris Longus

• Origin: Common flexor origin; may be absent.
• Insertion: Flexor retinaculum and apex of the palmar aponeurosis.
• Nerve supply: Median nerve.
• Actions: Flexion of the wrist joint.

Flexor Digitorum Superficialis

• Origin: By two heads:
• Humeroulnar head: Common flexor origin and medial border of coronoid process of the ulna.
• Radial head: From the oblique line and anterior border of the radius.
• Insertion: By 4 tendons into the palmar surface of middle phalanges of medial 4 fingers.
• Nerve supply: Median nerve.
• Actions:
• Flexion of the wrist joint.
• Flexion of the metacarpophalangeal and proximal interphalangeal joints of the medial four fingers.

Flexor Carpi Ulnaris

• Origin: By two heads:
• Humeral head: Common Flexor Origin
• Ulnar head: Medial border of the olecranon and the posterior border of the ulna.
• Insertion:
• Pisiform bone (main insertion).
• Hook of hamate through pisihamate ligament.
• Base of the 5th metacarpal bone through pisimetacarpal ligament.
• Nerve supply: Ulnar nerve.
• Actions:
• Flexion of wrist joint.
• Adduction of hand at wrist joint.

Ulnar Artery

• Beginning: One of the two terminal branches of the brachial artery in the cubital fossa at the level of the neck of the radius.
• Course:
• Descends medially deep to the deep head of pronator teres and separates it from the median nerve.
• Descends vertically deep to flexor carpi ulnaris and lateral to the ulnar nerve.
• Above wrist joint: runs between flexor carpi ulnaris and flexor digitorum superficialis, covered by skin, superficial fascia, and deep fascia (dangerous position); FDP (posterior).
• Enters the hand superficial to the flexor retinaculum and anastomoses with the superficial palmar branch of the radial artery to form the superficial palmar arch.

Radial Artery of the Forearm

• Beginning: One of the two terminal branches of the brachial artery in the cubital fossa at the level of the neck of the radius.
• End: In the palm of the hand as the deep palmar arch.
• Course: It passes deep to brachioradialis muscle with the radial nerve.
• In the lower one third, it descends on the distal end of the radius between brachioradialis muscle (laterally) and flexor carpi radialis (medially) and covered only by skin, superficial fascia, and deep fascia (where you can feel arterial pulsation).
• The radial pulse is most commonly used for feeling and counting arterial pulsations.
• Pulsations of the radial artery are easily palpated when the artery is compressed by the tips of the fingers against the distal end of the radius (bone).

Superficial Extensor Group

• The muscles in this group are arranged from lateral to medial.
• The muscles included in this group are Brachioradialis, Extensor Carpi Radialis Longus, Extensor Carpi Radialis Brevis, Extensor Digitorum, Extensor Digiti Minimi, Extensor Carpi Ulnaris, and Anconeus.
• Origin: Common extensor origin in front of the lateral epicondyle of the humerus, except for Brachioradialis, Extensor Carpi Radialis Longus, and Anconeus.
• Nerve Supply: Posterior interosseous nerve, except Brachioradialis, Extensor Carpi Radialis Longus, and Anconeus, which are supplied by the radial nerve.

Brachioradialis

• Origin: From the upper 2/3 of the lateral supracondylar ridge of the humerus.
• Insertion: Into the lateral side of the distal end of the radius at the base of the styloid process.
• Nerve Supply: Radial nerve.
• Actions:
• Initiates pronation and supination of the forearm.
• Flexion of the forearm in the midprone position.

Extensor Carpi Radialis Longus

• Origin: From the lower 1/3 of the lateral supracondylar ridge of the humerus.
• Insertion: Dorsum of the base of the 2nd metacarpal bone.
• Nerve supply: Radial nerve.
• Actions:
• Extension of the wrist.
• Abduction of the hand.

Extensor Carpi Radialis Brevis

• Origin: Common extensor origin.
• Insertion: Dorsum of the base of the 3rd metacarpal bone.
• Actions:
• Extension of the wrist.
• Abduction of the hand.

Extensor Digitorum

• Origin: Common extensor origin.
• Insertion: Four tendons to extensor expansions of the medial four fingers (middle and terminal phalanges).
• Actions: Extension of wrist and all joints of the medial 4 fingers.

Extensor Digiti Minimi

• Origin: Common extensor origin.
• Insertion: Into the extensor expansion of the little finger.
• Actions: Extension of wrist and all joints of the little finger.

Extensor Carpi Ulnaris

• Origin: Common extensor origin (humeral head) and posterior border of the shaft of the ulna.
• Insertion: Dorsum of the base of the 5th metacarpal bone.
• Actions:
• Extension of the wrist.
• Adduction of the hand.

Anconeus

• It is the only one of the superficial muscles that lies on the back of the elbow.
• Origin: Back of the lateral epicondyle of the humerus.
• Insertion: A triangular area on the lateral surface of the olecranon and upper part of the posterior surface of the ulna.
• Nerve Supply: Radial nerve through the nerve that supplied the medial head of the triceps muscle.
• Action: Extension of the elbow joint.

Deep Extensor Group

• The muscles included in this group are Supinator, Abductor Pollicis Longus, Extensor Pollicis Brevis, Extensor Pollicis Longus, and Extensor Indicis.
• The arrangement of the muscles is from lateral to medial.
• Nerve Supply: Posterior interosseous nerve.

Supinator

• Origin:
• Lateral epicondyle of the humerus.
• Radial collateral ligament.
• Annular ligament.
• Supinator fossa of the ulna.
• Supinator crest of the ulna.
• Insertion: Upper 1/3 of the anterior, lateral, and posterior surfaces of the shaft of the radius.
• Actions: Supination of the extended forearm.

Abductor Pollicis Longus

• Origin:
• Upper 1/3 of the posterior surface of the ulna.
• Middle 1/3 of the posterior surface of the radius.
• Interosseous membrane.
• Insertion: Base of the 1st metacarpal bone.
• Actions:
• Abduction of the thumb.
• Extension of the thumb.

Extensor Pollicis Brevis

• Origin:
• Lower 1/3 of the posterior surface of the radius.
• Interosseous membrane.
• Insertion: Base of the proximal phalanx of the thumb.
• Actions: Extension of the metacarpophalangeal joints of the thumb.

Extensor Pollicis Longus

• Origin:
• Middle 1/3 of the posterior surface of the ulna.
• Interosseous membrane.
• Insertion: Base of the terminal phalanx of the thumb.
• Actions:
• Extension of all joints of the thumb.
• Helps in abduction of the thumb.

Extensor Indicis

• Origin:
• Lower 1/3 of the posterior surface of the ulna.
• Interosseous membrane.
• Insertion: Extensor expansion of the index finger.
• Actions:
• Extension of all joints of the index finger.
• Helps in extension of the wrist.