Week 4: The Forearm and Wrist Flashcards
What is the main function of the muscles in the forearm?
flexion and extension of the wrist, fingers and thumbs
Which bones make up the wrist joint?
Articulation between: -distal radius -scaphoid -lunate Ulna is NOT involved
Which ligaments stregthen the wrist joint anteriorly and posteriorly?
radiocarpal ligaments
If you’re arm is supinated, (palm facing upwards) where do the radius and ulna lie?
-ulna lies medially and radius lies laterally (on the thumb side)
How is the radius and ulna connected?
by a strong interosseous membrane –> the IOM has holes in it for the passage of vessels
What is another word for wrist?
carpus
What are the names of the 8 bones of the carpus?
“So Long To Pinky, Here Comes The Thumb”
scaphoid lunate triquetral pisiform hamate capitate trapezoid trapezium
Which bones do we have in the hand (in ascending order)?
- Carpals (x8)
- Metacarpals
- Proximal phalanges
- Intermediate phalanges
- Distal phalanges
What is the joint between the carpals and metacarpals called?
carpometacarpal joint (CMCJ)
What is the joint between the metacarpals and proximal phalanges called?
Metacarpophalangeal (MCPJ)
What is the joint between the proximal phalanges and intermediate phalanges called?
proximal interpharangeal joint (PIPJ)
What is the joint between the intermediate phalages and distal phalanges called?
distal interphalangeal joint (DIPJ)
How is the thumb different to the other fingers?
-in the thumb, we have just two phalanges but in the fingers we have 3 (there is no intermediate phalange in the thumb)
What is the joint between the proximal phalange and distal phalange in the thumb called
interphalangeal joint
What is the function of the muscles in the anterior compartment of the forearm? (anterior compartment is when hand is supinated)
to flex (bend) the wrist and digits
What is the function of the muscles in the posterior compartment of the forearm? (anterior compartment is when hand is pronated)
to extend (straighten) wrist and digits
What movements are possible at the wrist joint?
- flexion
- extension
- abduction (waving toward you)
- adduction (waving away from you)
- circumduction
(adduction at fingers is to bring them together, abduction is to spread them out)
Which movements are possible at the thumb?
- abduction
- adduction
- extension
- flexion
- opposition
- reposition
(Abduction is different to extension as extension moves the thumb away from the hand in the same plane as the hand, abduction moves away )
Which nerve are most of the muscles in the anterior forearm innervated by?
median nerve (C5-T1) - the rest by the ulnar nerve
Where do the muscles of the anterior forearm insert?
medial epicondyle of the humerus: the ‘common flexor origin’
In the superficial layer of the anterior forearm, there are 4 muscles. 1 is a pronator and 3 are wrist flexors. What are their names?
- Pronator = pronator teres
- Wrist flexor = flexor carpi radialis
- Wrist flexor = flexor carpi ulnaris
- Wrist flexor = palmaris longus
Which nerves are the muscles in the superficial layer of the anterior forearm supplied by
All supplied by the median nerve except flexor carpi ulnaris (=ulnar nerve)
What muscle is found in the middle layer of the anterior forearm?
flexor digitorum superficialis
Where do the tendons of the flexor digitorum superficialis insert?
on the middle phalanx of digits 2-5
What is the function of the flexor digitorum superficialis?
- flexes the fingers at the proximal interphalangeal joint
- contributes to wrist flexion
Which nerve innervates the flexor digitorum superficialis?
median nerve
What are the 3 muscles found in the deep layer of the anterior forearm?
- Flexor digitorum profundus
- Flexor pollicis longus
- Pronator quadratus
Where does the flexor digitorum profundus insert and what is its function?
inserts on the distal phalanx and flexes the distal interphalangeal joint
Where does the flexor pollicis longus insert and what is its function?
inserts on the distal phalanx and flexes the interphalangeal joint (can also flex wrist)
Where does the pronator quadratus attach and what does it do?
- attachment to the distal radius and ulna
- pronates the forearm
Which nerves innervate the muscles in the posterior forearm?
radial nerve
Where do the muscles of the posterior forearm originate?
lateral epicondyle of the humerus: the ‘common extensor origin’
In the superficial layer of the posterior forearm, there are 6 muscles. There are 4 wrist extensors and 2 finger extensors. What are the names?
4 wrist extensors:
- extensor carpi radialis longus
- extensor carpi radialis brevis
- extensor carpi ulnaris
- brachioradialis
2 finger extensors:
- extensor digitorum
- extensor digiti minimi
Where does the extensor carpi radialis longus insert?
2nd metacarpal
Where does the extensor carpi radialis brevis insert?
3rd metacarpal
Where does the extensor carpi ulnaris insert?
5th metacarpal
Where does the extensor digitorum insert?
digits 2-5
Where does the extensor digiti minimi insert?
little finger
What is the extensor expansion?
fibrous structure where the finger extensors blend onto
Where does the supinator originate?
humerus and part of the ulnar
What is the function of the supinator?
helps to supernate the proximal radial joint
There are 5 muscles in the deep layer of the posterior forearm. There is 1 finger extensor, 2 thumb extensors and 1 thumb abductor. What are they called?
1 finger extensor: extensor indicis
2 thumb extensors:
- extensor pollicis longus
- extensor pollicis brevis
1 thumb abductor:
-abductor pollicis longus
Where does the extensor indices insert?
the extensor expansion on the dorsal aspect of the finger
Where does the extensor pollicis longus insert?
1st metacarpal
Where does the extensor pollicis brevis insert?
1st metacarpal
Where does the abductor pollicis longus insert?
1st metacarpal
What is the anatomical snuffbox?
a triangular deepening on the radial, dorsal aspect of hand
What are the borders of the anatomical snuffbox?
- extensor policies longus
- extensor policies brevis
- abductor policies longus
What are the terminal branches of the brachial artery?
radial and ulnar arteries
what does the ulnar artery branch into
common interosseous branches –> anterior interosseous and posterior inserosseous
What are the 2 major superficial veins that drain the hand?
cephalic (lateral) and basillic (medial)
Where does the cephalic vein form?
anatomical snuffbox
What is the carpal tunnel?
passageway in the wrist - the floor is the arch of the carpus, the roof is a fibrous sheet
What travels through the carpal tunnel?
long flexor tendons and the median nerve
What is carpal tunnel syndrome?
- compression of the median nerve
- sensory symptoms develop e.g pins and needles, tingling in areas of skin innervated by medialn nerve
- weakness in hand muscles innervated by median nerve (small muscles of thumb)
- weakness/ atrophy
