Muscles - Hand Flashcards
There are two groups of muscles of the hand: intrinsic and extrinsic. What are their functions?
Extrinsic - located in the anterior and posterior compartments of the forearm. They control forceful movements and produce a firm grip.
Intrinsic - these are located within the hand themself. They are responsible for fine motor functions of the hand.
What are the different muscle groups of the intrinsic muscles of the hand?
1) Thenar
2) Hypothenar
3) Lumbricals
4) Interrossei
5) Palmaris brevis + adductor pollicis
What are the thenar muscles?
These are located at the base of the thumb. The muscle bellies produce a bulge known as the thenar eminence. They are responsible for the fine movements of the thumb.
1) Opponens pollicis
2) Abductor pollicis brevis
3) Flexor pollicis brevis
The median nerve innervates these muscles.
Opponens pollicis
The largest of the three muscles. It lies underneath the other two muscles.
Origin - tubercle of the trapezium and the flexor retinaculum.
Insertion - lateral margin of the metacarpal of the thumb (the 1st metacarpal).
Actions - opposes the thumb, by medially rotating and flexing the metacarpal of the trapezium.
Innervation - median nerve.
Abductor pollicis brevis
It is found anterior to the opponens pollicis and proximal to the flexor pollicis brevis.
Origin - tubercles of the scaphoid and trapezium and flexor retinaculum.
Insertion - lateral side of proximal phalanx of the thumb.
Actions - abduction of the thumb.
Innervation - median nerve.
Flexor pollicis brevis
The most distal of the thenar muscles.
Origin - tubercle of the trapezium and flexor retinaculum.
Insertion - base of the proximal phalanx of the thumb
Actions - flexes the MCP joint of the thumb.
Innervation - median nerve
What are the hypothenar muscles?
These muscles produce the hypothenar eminence - a muscular protrusion of the medial side of the palm at the base of the little finger.
The ulnar nerve innervates these muscles.
1) Opponens digiti minimi
2) Abductor digiti minimi
3) Flexor digiti minimi brevis
Opponens digiti minimi
This lies deep to the other hypothenar muscles.
Origin - hook of hamate and flexor retinaculum.
Insertion - medial margin of metacarpal V.
Actions - it rotates the metacarpal of the little finger towards the palm, producing opposition.
Innervation - ulnar nerve
Abductor digiti minimi
The most superficial of the hypothenar muscles.
Origin - pisiform and tendon of the flexor carpi ulnaris.
Insertion - base of the proximal phalanx of the little finger.
Actions - abducts the little finger.
Innervation - ulnar nerve.
Flexor digiti minimi brevis
This lies laterally to the abductor digiti minimi.
Origin - hook of hamate and flexor retinaculum.
Insertion - base of the proximal phalanx of the little finger.
Actions - flexes the MCP joint of the little finger.
Innervation - ulnar nerve.
Lumbricals?
There are four lumbricals, each associated with each finger. They are crucial to finger movement, linking the extensor tendons to the flexor tendons.
Clinical relevance - denervation of these muscles is the basis for ulnar claw and hand benediction.
Origin - each lumbrical attach to the tendon of the flexor digitorum profundus.
Insertion - they pass dorsally and laterally around each finger and insert into the extensor hood.
Actions - flexes the MCP joint and extension at the IP joints of each digit.
Innervation - lateral lumbricals - median nerve. medial lumbricals - ulnar nerve.
Interossei?
The interrosei muscles are located between the metacarpals. They can be divided into the dorsal and palmar interossei.
Dorsal interossei
Most superficial of the dorsal muscles - can be palpated on the dorsum of the hand.
Origin - each interossei originate for the medial and lateral surfaces of the metacarpals.
Insertions - external hood and proximal phalanx of each finger
Actions - abducts the fingers at the MCP joint.
Innervation - ulnar nerve.
Palmar interossei
Located anteriorly of the hand. There are three palmar interossei muscles.
Origin - medial and lateral surface of a metacarpal
Insertion - extensor hood and proximal phalanx of the same finger.
Actions - adducts the finger at the MCP joint.
Innervation - ulnar nerve
Palmaris brevis
There is small thin muscle of the subcutaneous tissue of the hypothenar eminence.
Origin - palmar aponeurosis and flexor retinaculum.
Insertion - dermis of the skin on the medial margin of the hand.
Actions - wrinkles the skin of the hypothenar eminence and deepens the curvature of the hand, improving the grip.
Innervation - ulnar nerve
Adductor pollicis
Large triangular muscle with two heads. Radial artery passes between the two heads of this muscle, forming a deep palmar arch.
Origin - metacarpal III and capitate.
Insertion - base of proximal phalanx of the thumb.
Actions - adductor of the thumb.
Innervation - ulnar nerve.
