Intrinsic Muscles of the Hand and Carpal Tunnel Anatomy

Comprehensive vocabulary flashcards covering the intrinsic thenar, hypothenar, intermediate, and interosseous hand muscles, their origins, insertions, actions, innervations, and carpal tunnel anatomy.

"All For One" Mnemonic

A memory tip used to recall the hypothenar muscle group of the fifth digit, which consists of the abductor digiti minimi, flexor digiti minimi brevis, and opponens digiti minimi.

"One For All" Mnemonic

A memory tip used to recall the thenar muscle group of the thumb, which consists of the opponens pollicis, flexor pollicis brevis, and abductor pollicis brevis.

Abductor Digiti Minimi

A hypothenar muscle that originates from the pisiform and flexor carpi ulnaris tendon and inserts onto the base of the proximal phalanx to abduct the fifth digit at the MCP joint, innervated by the ulnar nerve.

Flexor Digiti Minimi Brevis

A hypothenar muscle originating from the hook of the hamate and flexor retinaculum that inserts onto the palmar side of the fifth proximal phalanx to flex the fifth finger and assist in opposition, innervated by the ulnar nerve.

Opponens Digiti Minimi

A deep hypothenar muscle originating from the hook of the hamate and flexor retinaculum that inserts on the ulnar shaft of the fifth metacarpal to assist in opposition, innervated by the ulnar nerve.

Opponens Pollicis

A thenar muscle originating from the flexor retinaculum and trapezium that inserts along the entire radial length of the first metacarpal to oppose the thumb at the CMC joint, innervated by the median nerve.

Flexor Pollicis Brevis

A thenar muscle with two heads: a superficial head innervated by the median nerve and a deep head originating from the distal carpal row innervated by the ulnar nerve, acting to flex the thumb and assist in opposition.

Abductor Pollicis Brevis

A thenar muscle originating from the flexor retinaculum, trapezium, and scaphoid tubercle that inserts onto the proximal phalanx to abduct the thumb and assist in opposition, innervated by the median nerve.

Lumbrical Muscles

Worm-like intrinsic hand muscles originating from the flexor digitorum profundus tendons that perform flexion at the MCP joints and extension at the PIP and DIP joints of digits two through five.

Extensor Hood (Extensor Expansion)

A specialized tendon expansion along the dorsal surface of the fingers where the lumbrical muscles insert to produce extension at the PIP and DIP joints.

Adductor Pollicis

A triangular muscle of the hand with an oblique head and a transverse head that pulls the thumb inward toward the third digit midline (adduction), innervated by the ulnar nerve.

Palmar Interossei (PAD)

A group of three intrinsic muscles between the metacarpals that adduct digits two, four, and five toward the third finger midline, innervated by the ulnar nerve.

Dorsal Interossei (DAB)

A group of four intrinsic muscles between metacarpals one through five that abduct digits two, three, and four away from the midline, innervated by the ulnar nerve.

Palmaris Brevis

The "plus one" intrinsic hand muscle originating from the flexor retinaculum and palmar aponeurosis that inserts directly into the skin of the ulnar palm to tighten grip and protect the underlying ulnar nerve.

Carpal Tunnel

An anterior wrist passageway bordered by the deep carpal arch bones and roofed by the flexor retinaculum that transmits flexor tendons and the median nerve.

LOAF (Half-LOAF) Mnemonic

A mnemonic identifying the hand muscles innervated by the median nerve: Lumbricals (lateral two, digits 2 and 3), Opponens pollicis, Abductor pollicis brevis, and Flexor pollicis brevis (superficial head).

Flexor Retinaculum

A dense fibrous tendon sheath bridging across the carpal bones that forms the roof of the carpal tunnel and provides attachment for intrinsic hand muscles.