6) Thumb Muscles Flashcards
Muscles acting on the hand can be divided into two groups:
Extrinsic
Intrinsic
Extrinsic muscles
The extrinsic muscles are located in the anterior and posterior compartments of the forearm. They control crude movements and produce a forceful grip.
Intrinsic muscles
The intrinsic muscles of the hand are located within the hand itself. They are responsible for the fine motor functions of the hand.
Boundaries of the anatomical snuff box
Lateral to medial
Tendon of Abductor pollicis longus
Tendon of Extensor pollicis brevis
Tendon of Extensor pollicis longus
Anatomical snuff box
Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus
Abductor pollicis longus
Deep to extensor brevis
O: mid 1/3 ulna,radius and Interosseous membrane
I: base of 1st metacarpal radial side
A: abducts thumb
F: thumbs up sign
NS: posterior Interosseous branch of radial nerve C7,8
Extensor pollicis brevis
Superficial to APL deep to EPL
O: mid posterior 1/3 radius and Interosseous membrane
I: base of 1st proximal phalanx dorsal surface
A: Extends CMP and MCP. Extends and abducts wrist
F: reaching for a jar
NS: posterior interossei branch of radial nerve C7,8
Extensor pollicis longus
Superficial to EPB
O: mid 1/3 ulna,radius and Interosseous membrane
I: base of 1st distal phalanx radial side
A: extends all thumbs joints and helps extend and abduct wrist
F: reaching for a jar
NS: Posterior interosseous branch of the radial nerve C7, 8
Flexor pollicis longus
Billy no mates
Only flexor of the distal phalanx
O: anterior surface of radius, between pronator quadratus and radial tuberosity and adjacent Interosseous membrane
I: base of 1st distal phalanx palmar surface
A: flexes distal phalanx of thumb
F: grip picking up anything
NS: anterior Interosseous branch median nerve C8 T1
Thenar
The thenar muscles are three short muscles 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.
Opponens pollicis
Abductor pollicis brevis
Flexor pollicis brevis
Opponens pollicis
Lies deep to APB FPB
O: trapezium tubercle and flexor retinaculum
I: length 1st metacarpal palmar aspect
A: opposes thumb
F: any gripping
NS: median nerve T1
Abductor pollicis brevis
O:scaphoid and trapezium tubercles and flexor retinaculum
I: base 1st proximal phalanx radial side
A: abducts thumb
F: opening hand preparing to grip a jar
NS: Median nerve T1
Flexor pollicis brevis
O: trapezium capitate and trapezoid tubercles and flexor retinaculum
I: base 1st proximal phalanx radial side
A: flexes MCP CMC joints
F: picking up and gripping
NS: median nerve T1
Hypothenar
The hypothenar muscles produce the hypothenar eminence - a muscular protrusion on the medial side of the palm, at the base of the little finger.
These muscles are similar to the thenar muscles in both name and organisation.
Flexor digiti minimi
Abductor digiti minimi
Opponens digiti minimi
Flexor digiti minimi
Most medial
O: hook of hamate and flexor retinaculum
I: base 5th proximal phalanx
A: flexes 5th MCP
F: opening hand preparing to grip jar
NS: median nerve T1
Abductor digiti minimi
Most lateral
O: pisiform and adjacent ligaments
I: base 5th proximal phalanx ulnar side and dorsal digital expansion
A: abducts little finger
F: preparing to pick up anything grip
NS: ulnar nerve T1
Opponens digiti minimi
Lies deep to Abd dm and Odm
O: hook of hamate and flexor retinaculum
I: 5th metacarpal palmar surface
A: opposes little finger
F: grip
NS: median nerve T1
Central compartment
Lumbricals
Dorsal interossei
Palmar interossei
Lumbricals
O: X4 tendons of flexor digitorum profundus: radial x2 are unipennate and ulnar x2 are bipinnate
I: extensor expansion radial side 2-5 digits
A: flex MCP and extend interphalangeal joints of fingers
NS: radial x2= median nerve // ulna x2= ulnar nerve
Dorsal Interossei
O: bipennate muscle shafts of adjacent metacarpals
I: dorsal digital expansions and proximal phalanx
A: 2,3,4 abducts MCP
F: preparing to and gripping large items
NS: ulnar nerve T1
Palmar Interosseoi
O: shafts of 2nd 4th and 5th metacarpals
I: dorsal digital expansions
A: palmar adducts the MCPs 1,2,4,5 digits
F: gripping
NS: ulnar nerve T1
How does flexion and extension occur at the lumbricals
Occurs because of the dorsal digital expansion
Insert into digital expansion helps link into different tendons ie extensor tendons
Fascia of the hand
Palmar aponeurosis
🔺dense fibrous tissue
Lies immediately deep to skin
Covers all tendons of long muscle in the palm
Apex: joined to flexor retinaculum at wrist may be joined by the tendon of palmaris longus
Base: at web of fingers: four slips pass distally to become fibrossous canals of the flexor tendons
Connects to capsule of MCP joints
Provide a semi rigid barrier between skin and tendons
It’s contraction increases grip
It serves to maintain tension in muscles and tendons and prevent bowstringing of tendons in the hand
