6) Thumb Muscles

Question 1

Muscles acting on the hand can be divided into two groups:

Answer 1

Extrinsic

Intrinsic

Question 2

Extrinsic muscles

Answer 2

The extrinsic muscles are located in the anterior and posterior compartments of the forearm. They control crude movements and produce a forceful grip.

Question 3

Intrinsic muscles

Answer 3

The intrinsic muscles of the hand are located within the hand itself. They are responsible for the fine motor functions of the hand.

Question 4

Boundaries of the anatomical snuff box

Answer 4

Lateral to medial

Tendon of Abductor pollicis longus

Tendon of Extensor pollicis brevis

Tendon of Extensor pollicis longus

Question 5

Anatomical snuff box

Answer 5

Abductor pollicis longus

Extensor pollicis brevis

Extensor pollicis longus

Question 6

Abductor pollicis longus

Answer 6

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

Question 7

Extensor pollicis brevis

Answer 7

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

Question 8

Extensor pollicis longus

Answer 8

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

Question 9

Flexor pollicis longus

Answer 9

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

Question 10

Thenar

Answer 10

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

Question 11

Opponens pollicis

Answer 11

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

Question 12

Abductor pollicis brevis

Answer 12

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

Question 13

Flexor pollicis brevis

Answer 13

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

Question 14

Hypothenar

Answer 14

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

Question 15

Flexor digiti minimi

Answer 15

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

Question 16

Abductor digiti minimi

Answer 16

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

Question 17

Opponens digiti minimi

Answer 17

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

Question 18

Central compartment

Answer 18

Lumbricals

Dorsal interossei

Palmar interossei

Question 19

Lumbricals

Answer 19

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

Question 20

Dorsal Interossei

Answer 20

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

Question 21

Palmar Interosseoi

Answer 21

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

Question 22

How does flexion and extension occur at the lumbricals

Answer 22

Occurs because of the dorsal digital expansion

Insert into digital expansion helps link into different tendons ie extensor tendons

Question 23

Fascia of the hand

Answer 23

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