Hand Anatomy Quiz

Hand Anatomy

• The hand's objective is to identify thenar and hypothenar eminences, and to describe the movements and nerve supply of hand muscles.
• Muscles of the thumb comprise the thenar eminence, while the little finger's muscles form the hypothenar eminence.
• Lumbricals and interossei are also hand muscles.
• Thenar eminence muscles include abductor pollicis brevis, flexor pollicis brevis, opponens pollicis, and adductor pollicis.
• Hypothenar eminence muscles comprise abductor digiti minimi, flexor digiti minimi, opponens digiti minimi, and palmaris brevis.
• Thumb movements include abduction, adduction, extension, flexion, and opposition. Abduction and adduction are perpendicular to the other four fingers, and extension and flexion are parallel.
• Lumbricals are small muscles originating from the flexor digitorum profundus tendon. Their nerve supply varies: the first two receive median nerves, and the last two receive ulnar nerves. Their action is flexion at the MCP joint and extension at the interphalangeal joints.
• Interossei (dorsal and palmar) muscles lie between metacarpal bones. The ulnar nerve supplies them. Their action is PAD (palmar adduction, dorsal abduction). The dorsal interossei are bipinnate.
• Palmaris brevis is a superficial muscle under the skin, whose ulnar nerve supply helps with gripping. It also improves hand grip by making the hypothenar eminence prominent.

Nerve Injuries - Upper Limb

• Brachial plexus injuries include Erb palsy ("waiter's tip") and Klumpke palsy.

  • Erb palsy is associated with traction/tear of upper trunk (C5-C6 roots).
  • Klumpke palsy is linked to traction/tear of lower trunk (C8-T1 roots).

• Musculocutaneous nerve originates from the lateral cord (C5,6,7). It passes between biceps brachii and brachialis muscles and supplies coracobrachialis, biceps, and brachialis muscles and skin of the lateral forearm.

• Axillary nerve originates from posterior cord of the brachial plexus, exits the axilla, innervates deltoid and teres minor muscles, and supplies sensation to skin over the deltoid muscle.

• Median nerve is lateral to the axillary artery and anterior to the elbow joint. It passes between the pronator teres heads, the deep surface of flexor digitorum superficialis, enters the palm through the carpal tunnel, and is deep to the flexor retinaculum.

• Median nerve branches in the forearm supply pronator teres, flexor carpi radialis, palmaris longus, and flexor digitorum superficialis, and have articular branches for the elbow joint.

  • Palmar cutaneous branch supplies the lateral 2/3 of palm skin, isn't affected by carpal tunnel syndrome.

• Ulnar nerve is medial to the axillary artery and passes posterior to the medial epicondyle of the humerus. In the forearm, it passes between the flexor carpi ulnaris heads. It passes between flexor carpi ulnaris and flexor digitorum profundus muscles at the wrist. Ulnar nerve branches in the forearm supply flexor carpi ulnaris and the medial half of flexor digitorum profundus. The palmar branch supplies medial palm skin, and the dorsal branch supplies medial dorsal hand and 1 1/2 medial fingers skin. Superficial branch supplies palmaris brevis and the medial 11/2 skin of the palm. The deep branch supplies interossei, adductor pollicis, and the first two lumbricals.

• Radial nerve originates in the lower triangular space, accompanies profunda brachii artery. It crosses the radial groove medially to laterally. It appears in the forearm between the brachialis and brachioradialis muscles. It divides into deep and superficial branches. The superficial branch supplies skin of lateral 2/3 of the dorsal hand and the skin of lateral 3 ½ fingers, except the distal phalanges. Deep branches supply brachialis, triceps, anconeus, brachioradialis, and extensor carpi radialis longus.

Additional information

• References are provided for further research.