ts of forearm
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anatomical transverse section of forearm showing flexor and extensor compartments radius ulna interosseous membrane
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forearm anatomy
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transverse section forearm anatomy flexor extensor compartments radius ulna
Transverse section of the forearm
A transverse section shows the forearm divided by the radius, ulna, interosseous membrane, deep fascia, and intermuscular septa into flexor and extensor compartments.
1. Bones and membrane
- Radius: lateral side, or thumb side
- Ulna: medial side, or little-finger side
- Interosseous membrane: strong fibrous sheet joining the two bones; separates deep flexor and extensor structures and transmits forces between radius and ulna.
2. Anterior compartment - flexor-pronator compartment
Located anterior to the radius, ulna, and interosseous membrane.
Superficial muscles
- Pronator teres
- Flexor carpi radialis
- Palmaris longus
- Flexor carpi ulnaris
- Flexor digitorum superficialis
Deep muscles
- Flexor digitorum profundus
- Flexor pollicis longus
- Pronator quadratus, near the distal forearm
Nerves and vessels
- Median nerve: usually between flexor digitorum superficialis and profundus
- Ulnar nerve and ulnar artery: medial side, near flexor carpi ulnaris
- Radial artery: lateral side, deep to brachioradialis
- Anterior interosseous nerve and artery: on the anterior surface of the interosseous membrane
3. Posterior compartment - extensor-supinator compartment
Located posterior to the radius, ulna, and interosseous membrane.
Superficial muscles
- Extensor digitorum
- Extensor digiti minimi
- Extensor carpi ulnaris
- Extensor carpi radialis longus and brevis
- Brachioradialis, on the lateral side
Deep muscles
- Supinator
- Abductor pollicis longus
- Extensor pollicis brevis
- Extensor pollicis longus
- Extensor indicis
Nerve and vessels
- Posterior interosseous nerve, the continuation of the deep branch of radial nerve
- Posterior interosseous artery
Easy orientation in a diagram
- Anterior side: bulk of flexor muscles, median and ulnar neurovascular bundles
- Posterior side: extensor muscle mass
- Lateral/radial side: brachioradialis and radial artery
- Medial/ulnar side: flexor carpi ulnaris with ulnar nerve and artery
The forearm is conventionally described as having anterior flexor and posterior extensor compartments, as summarized in this cross-sectional anatomy review.
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