The Hand Flashcards
What does prehensile mean?
Capable of grasping
What type of joints are the small joints of the hand? What disesase does this mean they are therefore vulnerable to?
Synovial joints
Vulnerable to rheumatoid arthritis - when the immune system attacks lining of the joints (called the synovium)
What joint is circled?
Carpometacarpal joint
Surface anatomy of the hand
What joints are the ‘knuckles’?
The metacarpophalangeal joints
What 2 groups of muscles bring about movements of the fingers and thumb?
- Extrinsic muscles
- Intrinsic muscles
Where are the extrinsic muscles of the hand found?
Located in the anterior and posterior compartments of the forearm whose tendons travel down into the hand
Where are the tendons of the extrinsic muscles of the hand most vulnerable?
Most vulnerable to injury at the wrist or in the hand
Where are the intrinsic muscles of the hand located?
Both their origins and insertions are located within the hand itself. These are, by definition, short, or small muscles. Many of them have the term ‘brevis’ in their name.
Broadly, what type of movements are the extrinsic / intrinsic muscles of the hand responsible for?
Extrinsic - They control crude movements and produce a forceful grip.
Intrinsic - They are responsible for the fine motor functions of the hand.
Where do almost all of the intrinsic muscles of the hand lie?
Almost all of them lie in the palm of the hand (the dorsum of the hand has just one set)
Describe the organisation of the intrinsic muscles of the hand
- 4 groups of muscles
- 1 single muscle
What are the 4 groups of intrinsic muscles?
- Thenar muscles
- Hypothenar muscles
- Lumbricals
- Interosseous muscles (interossei)
What is the single intrinsic muscle?
Adductor pollicis
How many muscles make up the ‘thenar’ muscle group? Where do they lie? What is their function?
- 3 muscles that lie in the palm of the hand at the base of the thumb
- Produce the bulge - ‘thenar eminence’
- Responsible for fine movements of the thumb
What innervates the thenar muscles?
The recurrent branch of the median nerve
How many muscles make up the ‘hypothenar’ muscle group? Where do they lie? What is their function?
- 3 muscles that lie in the palm at the base of the little finger
- Make up the ‘hypothenar eminence’
- Move the little finger (mirror the thenar eminence muscles)
What are the hypothenar muscles innervated by?
By the deep branch of the ulnar nerve
How many muscles make up the ‘lumbrical’ muscle group? Where do the lumbricals arise from?
- 4
- Don’t have a bony attachment but instead arise from the tendons of the flexor digitorum profundus
- FDP gives off 4 tendons in the palm
How many muscles make up the ‘interosseous’ muscle group? Where do they lie?
- 7
- 3 in the palm
- 4 in the dorsum
- These lie between adjacent metacarpal bones
What are the lumbricals innervated by?
The lateral two lumbricals (of the index and middle fingers) are innervated by the median nerve. The medial two lumbricals (of the little and ring fingers) are innervated by the ulnar nerve.
What are the interossei muscles innervated by?
The ulnar nerve
Where does adductor pollicis lie? What is its action?
A single muscle that lies in the palm and adducts the thumb
What is adductor pollicis innervated by?
The ulnar nerve
What intrinsic muscles of the hand does the ulnar nerve innervate?
- Hypothenar muscles
- Interossei muscles
- Medial 2 lumbrical muscles (4th and 5th digits)
- Adductor pollicis
What intrinsic muscles of the hand does the median nerve innervate?
- Thenar muscles
- Lateral 2 lumbrical muscles (2nd and 3rd digits)
Does the radial nerve innervate any intrinsic muscles of the hand?
No
What are the muscles of the ‘thenar’ eminence?
- Opponens pollicis
- Flexor pollicis brevis
- Abductor pollicis brevis
What muscle of the thenar eminence is the largest? Which lies the deepest?
The opponens pollicis is the largest of the thenar muscles, and lies underneath the other two.
Where do the muscles of the thenar eminence originate?
From the carpal bones (centered on the trapezium)
What is the trapezium?
The trapezium bone is a carpal bone in the hand
What is the action of opponens pollicis brevis?
Opposes the thumb, by medially rotating and flexing the metacarpal on the trapezium.
Where does opponens pollicis brevis insert?
On the 1st metacarpal
Action of abductor pollicis brevis?
Abducts the thumb.
Where does abductor pollicis brevis insert?
Attaches to the base of the proximal phalanx of the thumb.
Action of flexor pollicis brevis?
Flexes the metacarpophalangeal (MCP) joint of the thumb.
Where does flexor pollicis brevis insert?
Attaches to the base of the proximal phalanx of the thumb.
Describe relation of flexor and abductor pollicis brevis
Flexor pollicis brevis lies slightly more medially
Abductor pollicis brevis lies slightly more laterally
Both lie superficial to the opponens pollicis
Name the highlighted muscle
Flexor pollicis brevis
Name the muscle highlighted in blue
Abductor pollicis brevis
What nerve is being pointed to? What type of nerve is this?
Recurrent branch of the median nerve - motor nerve
This prosection provides a deep view of the thumb. What muscle is highlighted in pink?
Opponens pollicis (lies deep to abductor)
What are the names of the 3 muscles of the hypothenar eminence?
- Opponens digiti minimi
- Abductor digiti minimi
- Flexor digiti minimi brevis
N.B. the names of the thenar muscles have just been replaced with ‘digiti minimi’
Where do the hypothenar eminence muscles originate?
Carpal bones (centered on the hamate and pisiform)
Describe locations of the 3 hypothenar muscles?
ODM - lies deep to the others
ADM - most superficial
FDM - lies laterally to the ADM
Where does opponens digiti minimi insert?
On the 5th metacarpal (shown in diagram with opposing thenar muscle)
Action of ODM?
It rotates the metacarpal of the little finger towards the palm, producing opposition.
Where does abductor digiti minimi insert?
It attaches to the base of the proximal phalanx of the little finger (5th digit)
(shown in diagram with opposing thenar muscle)