Muscles of the Hand

gotta hand it to ya

Intrinsic Muscles of the Hand

the intrinsic muscles of the hand can be divided into 5 compartments

Thenar Compartment

• abductor pollicis brevis

• flexor pollicis brevis

• opponens pollicis

Adductor Compartment

• adductor pollicis

Hypothenar Compartment

• abductor digiti minimi

• flexor digiti minimi brevis

• opponens digiti minimi

Central Compartment

• Lumbricals (4)

Interosseous Compartment

• dorsal interossei (4)

• palmar interossei (3)

Flexor Retinaculum (transverse carpal ligament)

• a strong, fibrous band of connective tissue in the wrist that bridges the arch of the carpal bones to form the roof of the carpal tunnel

• protects the 9 forearm flexor tendons and the median nerve

• attaches medially to the pisiform and the hook of hamate

• attaches laterally to the tubercle of the scaphoid and the trapezium

abductor pollicis brevis

• the thenar muscles form an elevation located on the radial (lateral) aspect of the palm called the thenar eminence

• abductor pollicis brevis is the most lateral and most superficial of the thenar muscles

• runs from the scaphoid and trapezium to the proximal phalanx of the thumb

origin → tubercles of scaphoid and trapezium, flexor retinaculum

insertion → lateral aspect of base of proximal phalanx 1 (via radial sesamoid bone)

action → thumb abduction at carpometacarpal joint 1

innervation → recurrent branch of median nerve (C8, T1)

blood supply → superficial palmar branch of radial artery

flexor pollicis brevis

• a short, broad thenar muscle composed of superficial and deep heads

• the deep head can vary in size and sometimes be absent

origin → superficial head: flexor retinaculum, tubercle of trapezium bone

→ deep head: trapezoid and capitate bones

insertion → lateral aspect of base of proximal phalanx (via radial sesamoid bone)

action → thumb flexion at carpometacarpal and metacarpophalangeal joints

innervation → superficial head: recurrent branch of median nereve

→ deep head: deep branch of ulnar nerve (C8, T1)

blood supply → superficial palmar artery, princeps pollicis artery, radialis indicis artery

opponens pollicis

• a short thenar muscle that functions to oppose the thumb

origin → tubercle of trapezium bone, flexor retinaculum

insertion → radial border of metacarpal bone 1

action → thumb opposition at carpometacarpal joint 1

innervation → recurrent branch of median nerve (C8, T1)

blood supply → superficial palmar branch of radial artery

adductor pollicis

• composed of 2 heads and functions to adduct the thumb

origin → transverse head: palmar base of metacarpal bone 3

→ oblique head: capitate bone, palmar base of metacarpal bones 2&3

insertion → medial base of proximal phalanx 1 (via ulnar sesamoid bone)

action → thumb adduction at carpometacarpal joint 1

innervation → deep branch of ulnar nerve (C8, T1)

blood supply → deep palmar arch

abductor digiti minimi

• a short muscle in the hypothenar group

• main function is abduction of the 5th finger

• also flees the proximal phalanx

• forms the hypothenar eminence on the medial side of the palm along with the other hypothenar muscles

origin → pisiform bone (pisohamate ligament, tendon of flexor carpi ulnaris)

insertion → ulnar side of base of proximal phalanx of digit 5, extensor expansion of digit 5

action → finger abduction and flexion at the metacarpophalangeal joint 5, finger extension at the interphalangeal joints

innervation → deep branch of ulnar nerve (C9, T1)

blood supply → palmar branch of ulnar artery, palmar digital artery, superficial palmar arch

flexor digiti minimi brevis

• a short hypothenar group muscle that sperads from the hook of hamate and flexor retinaculum to the base of the proximal phalanx of the little finger

• main function is flexion of the little finger

origin → hook of hamate, flexor retinaculum

insertion → base of proximal phalanx of digit 5

action → finger flexion (and finger lateral rotation/opposition) at the metacarpophalangeal joint 5

innervation → deep branch of ulnar nerve (C8, T1)

blood supply → deep palmar branch of ulnar artery

opponens digiti minimi

• extends between the hamate and 5th metacarpal to help with flexion, lateral rotation, and opposition of the little finger which is important for grip

origin → hook of hamate bone, flexor retinaculum

insertion → ulnar aspect of metacarpal bone 5

action → finger flexion, finger lateral rotation/opposition at carpometacarpal joint 5

innervation → deep branch of ulnar nerve (C8, T1)

blood supply → deep palmar branch of ulnar artery, deep palmar arch

lumbricals

• the lumbrical muscles are 4 short intrinsic hand muscles located between the metacarpal bones, deep to the palmar fascia

• flex the fingers at the metacarpophalangeal joints and extend them at the interphalangeal joints

• important for gripping

origin → tendons of flexor digitorum profundus muscle

insertion → extensor expansion of hand

action → finger flexion at metacarpophalangeal joints 2-5, finger extension at interphalangeal joints 2-5

innervation → lumbricals 1-2: median nerve (C8-T1)

→ lumbricals 3-4: ulnar nerve (C8-T1)

→ mnemonic: '1 2 me, 3 4 u' (One to me, three for you)

blood supply → dorsal carpal arch, superficial palmar arch

dorsal interossei

• the dorsal interossei are short, bipennate intrinsic hand muscles found on the dorsal aspect of the hand occupying the space between the metacarpals, along with the palmar interossei

• consist of 4 short muscles that attach to the adjacent sides of metacarpals 1-4

• abduct digits 2-4 and assist in extension at the interphalangeal joints

origin → adjacent sides of metacarpal bones 1-5

insertion → 1&2: radial bases of proximal phalanges/extensor expansion of digits 2&3

→ 3&4: ulnar bases of proximal phalanges/extensor expansions of digits 3&4

action → finger abduction and flexion at metacarpophalangeal joints 2-4, finger extension at interphalangeal joints 2-4

innervation → deep branch of ulnar nerve (C8-Th1)

blood supply → 1: first dorsal metacarpal artery (radial artery)

→ 2, 3, &4: second, third, and fourth dorsal metacarpal arteries (dorsal carpal anastomosis)

palmar interossei

• short, unipennate intrinsic hand muscles that lie on the palmar surface and occupy the spaces between metacarpal bones

• consist of 4 muscles that attach to the 1st, 2nd, 4th, and 5th finger

• strong adductors of the fingers

• greatly contribute to flexion and extension of fingers 2, 4, and 5

origin → ulnar side of metacarpal bone 2, radial side of metacarpal bones 4 and 5

insertion → 1: ulnar base of proximal phalanx/extensor expansion of digit 2

→ 2&3: radial base of proximal phalanges/extensor expansions of digits 4&5

action → finger adduction and flexion at metacarpophalangeal joints 2, 4, 5 and finger extension at interphalangeal joints 2, 4, 5

→ mnemonic:  PAD DAB ('Use your hand to dab with a pad') - Palmar interossei ADduct, Dorsal interossei ABduct

innervation → deep branch of ulnar nerve (C8-T1)

blood supply → deep palmar arch, princeps pollicis artery, radialis indicis artery, palmar metacarpal arteries, proximal and distal perforating arteries, common and proper palmar arteries