Upper limb gross anatomy 3: Flexors and extensors of the forearm and the wrist

Question 1

What ligament holds the head of the radius in place?

Answer 1

Annular ligament

Question 2

Which carpal bones articulate with the radius?

Answer 2

Scapoid and lunate

Question 3

Where can you palpate the scaphoid bone? What would pain and tenderness in the area indicate?

Answer 3

Can be palpated at the base of the anatomical snuffbox. Pain and tenderness may indicate a fracture.

Question 4

Describe the blood supply to the scaphoid. What implications may fracture of the scaphoid have on its blood supply?

Answer 4

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.

Question 5

What effect would median nerve damage at the level of the wrist have on movements of the fingers/thumb?

Answer 5

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.

Question 6

What are the contents of the cubital fossa?

Answer 6

Biceps brachii tendon, brachial artery, median nerve

Question 7

What effect would damage to the median nerve in the cubital fossa have on the movements of the upper limb?

Answer 7

Pronator teres syndrome -> weakness of flexor pollicis longus, flexor digitorum profundus and pronator quadratus. Pain/numbness in the distribution of distal median nerve.

Question 8

Where does flexor carpi ulnaris attach distally?

Answer 8

Pisiform bone then via pisohamate and pisometacarpal ligaments into hamate and base of metacarpal 5.

Question 9

Where does flexor carpi radialis attach distally?

Answer 9

Base of metacarpals 2 and 3.

Question 10

Other than flexion of the wrist, what actions do flexor carpi radialis and ulnaris produce?

Answer 10

Ulnaris - adduction

Radialis - abduction

Question 11

What is the nerve supply to the superficial flexors of the wrist?

Answer 11

Pronator teres - median nerve
Flexor carpi radialis - median nerve
Palmaris longus - median nerve
Flexor carpi ulnaris - ulnar nerve

Question 12

What is the nerve supply to brachioradialis?

Answer 12

Radial nerve -> C5-6, before division into superficial and deep branches

Question 13

Why is brachioradialis unusual?

Answer 13

Muscle is a flexor but muscle is part of posterior compartment and innervated by radial nerve.

Question 14

What is the intermediate flexor of the forearm?

Answer 14

Flexor digitorum superficialis

Question 15

To which phalanges does flexor digitorum superficialis attach?

Answer 15

Middle phalanges of index, middle, ring and little fingers.

Question 16

Where does the median nerve lie in relation to flexor digitorum superficialis?

Answer 16

Passes deep to it between the two heads.

Question 17

What are the deep flexors of the forearm?

Answer 17

Flexor pollicis longus
Flexor digitorum profundus
Pronator quadratus

Question 18

What are the superficial flexors of the forearm?

Answer 18

Pronator teres
Flexor carpi radialis
Palmaris longus
Flexor carpi ulnaris

Question 19

Where do the tendons of flexor digitorum profundus insert?

Answer 19

Palmar surfaces of distal phalanges of index, middle, ring and little fingers.

Question 20

What is the interosseous membrane and where is it located?

Answer 20

Broad and thin plane of fibrous tissue in between radius and ulna.

Question 21

What are the roles of the interosseous membrane?

Answer 21

• Divides forearm into anterior and posterior compartments
• Site of attachment for muscles
• Transfers force from radius to ulna to humerus
• Tense during supination

Question 22

What structures pass through the carpal tunnel?

Answer 22

Flexor digitorum profundus tendons
Flexor digitorum superficialis tendons
Median nerve
Flexor pollicis longus tendons

Question 23

What is carpal tunnel syndrome?

Answer 23

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.

Question 24

What are the superficial extensors?

Answer 24

Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor digitorum (communis)
Extensor digiti minimi
Extensor carpi ulnaris

Question 25

Describe the distal attachments of extensor digitorum.

Answer 25

Inserts via extensor hoods into dorsal aspect of bases of middle and distal phalanges of index, middle, ring and little fingers.

Question 26

From where does aconeus arise?

Answer 26

Lateral epicondyle of the humerus.

Question 27

Where does anconeus insert?

Answer 27

Olecranon and proximal posterior surface of ulna.

Question 28

What is the function of aconeus?

Answer 28

Abduction of ulna in pronation, accessory extensor in joint of elbow.

Question 29

What does extensor carpi ulnaris insert?

Answer 29

Base of 5th metacarpal.

Question 30

Where does extensor carpi brevis insert?

Answer 30

Bases of 2nd and 3rd metacarpals.

Question 31

Where does extensor carpi radialis insert?

Answer 31

Base of 2nd metacarpal.

Question 32

What are the deep extensors of the forearm?

Answer 32

Extensor indicis
Extensor pollicis brevis
Extensor pollicis longus
Abductor pollicis
Supinator

Question 33

Which artery can be palpated in the anatomical snuffbox?

Answer 33

Radial artery

Question 34

What are the attachments of pronator teres?

Answer 34

Proximal, humeral head - medial epicondyle, adjacent supra-epicondylar ridge
Proximal, ulnar head - medial side of coronoid process

Question 35

What are the attachments of pronator quadratus?

Answer 35

Proximal - linear ridge on distal anterior surface of ulna

Distal - distal anterior surface of radius

Question 36

What are the attachements of supinator?

Answer 36

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