Upper limb gross anatomy 3: Flexors and extensors of the forearm and the wrist Flashcards
What ligament holds the head of the radius in place?
Annular ligament
Which carpal bones articulate with the radius?
Scapoid and lunate
Where can you palpate the scaphoid bone? What would pain and tenderness in the area indicate?
Can be palpated at the base of the anatomical snuffbox. Pain and tenderness may indicate a fracture.
Describe the blood supply to the scaphoid. What implications may fracture of the scaphoid have on its blood supply?
Lateral and distal branches of the radial artery. Blood flows from the distal end of the bone in a retrograde fashion down to the proximal pole. If blood flow is disrupted by a fracture the bone may not heal.
What effect would median nerve damage at the level of the wrist have on movements of the fingers/thumb?
Lack of ability to abduct and oppose the thumb due to paralysis of the thenar muscles. This is called “ape-hand deformity”.
Sensory loss in the thumb, index finger, long finger, and the radial aspect of the ring finger
Weakness in forearm pronation and wrist and finger flexion.
Activities of daily living such as brushing teeth, tying shoes, making phone calls, turning door knobs and writing, may become difficult with a median nerve injury.
What are the contents of the cubital fossa?
Biceps brachii tendon, brachial artery, median nerve
What effect would damage to the median nerve in the cubital fossa have on the movements of the upper limb?
Pronator teres syndrome -> weakness of flexor pollicis longus, flexor digitorum profundus and pronator quadratus. Pain/numbness in the distribution of distal median nerve.
Where does flexor carpi ulnaris attach distally?
Pisiform bone then via pisohamate and pisometacarpal ligaments into hamate and base of metacarpal 5.
Where does flexor carpi radialis attach distally?
Base of metacarpals 2 and 3.
Other than flexion of the wrist, what actions do flexor carpi radialis and ulnaris produce?
Ulnaris - adduction
Radialis - abduction
What is the nerve supply to the superficial flexors of the wrist?
Pronator teres - median nerve
Flexor carpi radialis - median nerve
Palmaris longus - median nerve
Flexor carpi ulnaris - ulnar nerve
What is the nerve supply to brachioradialis?
Radial nerve -> C5-6, before division into superficial and deep branches
Why is brachioradialis unusual?
Muscle is a flexor but muscle is part of posterior compartment and innervated by radial nerve.
What is the intermediate flexor of the forearm?
Flexor digitorum superficialis
To which phalanges does flexor digitorum superficialis attach?
Middle phalanges of index, middle, ring and little fingers.
Where does the median nerve lie in relation to flexor digitorum superficialis?
Passes deep to it between the two heads.
What are the deep flexors of the forearm?
Flexor pollicis longus
Flexor digitorum profundus
Pronator quadratus
What are the superficial flexors of the forearm?
Pronator teres
Flexor carpi radialis
Palmaris longus
Flexor carpi ulnaris
Where do the tendons of flexor digitorum profundus insert?
Palmar surfaces of distal phalanges of index, middle, ring and little fingers.
What is the interosseous membrane and where is it located?
Broad and thin plane of fibrous tissue in between radius and ulna.
What are the roles of the interosseous membrane?
- Divides forearm into anterior and posterior compartments
- Site of attachment for muscles
- Transfers force from radius to ulna to humerus
- Tense during supination
What structures pass through the carpal tunnel?
Flexor digitorum profundus tendons
Flexor digitorum superficialis tendons
Median nerve
Flexor pollicis longus tendons
What is carpal tunnel syndrome?
Compression of median nerve in carpal tunnel -> parasthesia and/or numbness in the median nerve distribution of the hand (thumb, index finger, middle and radial side of ring finger). Aching in the thenar eminence and weakness/atrophy of the abductor pollicis brevus and opponens pollicis.
What are the superficial extensors?
Extensor carpi radialis longus Extensor carpi radialis brevis Extensor digitorum (communis) Extensor digiti minimi Extensor carpi ulnaris
Describe the distal attachments of extensor digitorum.
Inserts via extensor hoods into dorsal aspect of bases of middle and distal phalanges of index, middle, ring and little fingers.
From where does aconeus arise?
Lateral epicondyle of the humerus.
Where does anconeus insert?
Olecranon and proximal posterior surface of ulna.
What is the function of aconeus?
Abduction of ulna in pronation, accessory extensor in joint of elbow.
What does extensor carpi ulnaris insert?
Base of 5th metacarpal.
Where does extensor carpi brevis insert?
Bases of 2nd and 3rd metacarpals.
Where does extensor carpi radialis insert?
Base of 2nd metacarpal.
What are the deep extensors of the forearm?
Extensor indicis Extensor pollicis brevis Extensor pollicis longus Abductor pollicis Supinator
Which artery can be palpated in the anatomical snuffbox?
Radial artery
What are the attachments of pronator teres?
Proximal, humeral head - medial epicondyle, adjacent supra-epicondylar ridge
Proximal, ulnar head - medial side of coronoid process
What are the attachments of pronator quadratus?
Proximal - linear ridge on distal anterior surface of ulna
Distal - distal anterior surface of radius
What are the attachements of supinator?
Proximal, superficial - humeral head originates from lateral epicondyle of humerus annular ligament, radial collateral ligament
Proximal, deep - ulnar head originates from supinator crest on the posterior lateral surface of the ulna
Distal - lateral surface of radius superior to the anterior oblique line
