- Thenar Muscles of the Hand these are all supplied by the recurrent branch of the median nerve and together their synergistic actions lead chiefly to opposition of the thumb, which is its most important movement.
The thenar eminence contains three muscles
- The abductor pollicis brevis-
- “Short thumb abductor”
- Supplied by the median nerve
- Among peripheral nerve entrapments, entrapment of the median nerve is the most common which occurs at the wrist. Since this entrapment occurs from swelling and inflammation of the tissues in the “Carpal Tunnel” this entrapment condition is known as Carpal Tunnel Syndrome.
- During severe and prolonged cases atrophy of the abductor pollicis brevis can occur along with the other muscles of the thenar eminence supplied by the median nerve, severely limiting movement of the thumb.
- Flexor pollicis brevis
- Causes flexion of the thumb
- Its superficial part originates from the distal border of the flexor retinaculum and the tubercle of the trapezium.
- The deeper part originates from the capitate and trapezoid bones.
- Opponens pollicis
- It flexes and abducts the first metacarpal joint with medial rotation at the hand
Hypothenar Muscles of the Hand–
These muscles are supplied by the ulnar nerve
- abductor digiti minimi-
- assists with flexion of the fifth metacarpal joint
- originates on the pisiform, the pisohamate ligament, and the flexor retinaculum.
- inserts on the medial side of the base of the proximal phalanx of the little finger.
- flexor digiti minimi brevis
- opponens digiti minimi
Interossei Muscles of the Hand
- There are seven interossei muscles, with two layers: three palmar and four dorsal.
- Palmar Interossei Muscles
- four palmar interossei muscles between the metacarpals, one going to the thumb, index, ring, and little fingers. These muscles help in adduction of the fingers.
- The first palmar interossei of the thumb also assists the flexor pollicis brevis with flexion of the thumb.
- The remaining three also assist the lumbricales in flexing the metacarpophalangeal joint and extending both interphalangeal joints
- Dorsal Interossei Muscles
- There are four muscle, each originating from two heads, one for each side of the adjacent metacarpal bones of the index, middle, ring and little finger.
- These muscles abduct the fingers and also assist the lumbricals in flexion and extension of the joints
This mnemonic recalls the function of the palmar and dorsal interossei:PAd DAb
- four slender muscles resemble an earthworm in shape, size and color.
- highly active during any activity requiring active extension of the interphalangeals
- used to place the fingers into the writing position