Forearm and hand II week 3

Question 1

What layers are the muscles in the posterior compartment of the forearm divided into? What are their general functions?

Answer 1

1. superficial and deep layers
2. movements of the wrist joint, extension of the fingers including the thumb, and supination of the forearm

Question 2

What are the common origins of muscles in the posterior compartment of the forearm?

Answer 2

lateral epicondyle and supracondylar ridge

Question 3

What muscle in the posterior compartment of the forearm is an exception to the extensor functions of the muscles in this group?

Answer 3

brachioradialis. it is a flexor of the forearm at the elbow when the forearm is in a neutral position btwn pronation and supination (picture a handshake). note that it does not cross the wrist joint

Question 4

All muscles in the posterior compartment of the arm are innervated by the _____ nerve or one of its branches.

Answer 4

radial

Question 5

What muscles are in the superficial layer of the posterior compartent of the forearm?

Answer 5

from lateral to medial: brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris

note that there is only a single extensor digitorum muscle (unlike the supericial and deep flexor digitorum muscles). therefore, we have less control over the extension of our fingers than flexion

also, note that tendons of the extensor digitorum are interconnected as they pass to individual digits

Question 6

What muscles are in the deep layer of the posterior comparment of the forearm?

Answer 6

note that there is no intermediate layer of the posterior forearm as there is in the anterior forearm

from lateral to medial: supinator (pierced by the deep branch of the radial nerve), abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis

Question 7

What is the origin, insertion, function, and innervation of the anconeus?

Answer 7

origin: lateral epicondyle of humerus
insertion: olecranon process of ulna
function: extension of the forearm at the elbow
innervation: radial nerve

Question 8

What is the origin, insertion, function, and innervation of the brachioradialis?

Answer 8

origin: lateral supracondylar ridge of humerus
insertion: stlyoid process of radius (distal end of radius
function: flexes forearm at the elbow
innervation: radial nerve

Question 9

What is the origin, insertion, function, and innervation of the extensor carpi radialis longus?

Answer 9

origin: lateral supracondylar ridge of humerus
insertion: base of 2nd metacarpal
function: extends and abducts the wrist at the radiocarpal joint
innervation: radial nerve

Question 10

What is the origin, insertion, function, and innervation of the extensor carpi radialis brevis?

Answer 10

origin: lateral epicondyle of humerus
insertion: base of 3rd metacarpal
function: extends and abducts the wrist at the radiocarpal joint
innervation: radial nerve

Question 11

What is the origin, insertion, function, and innervation of the extensor digitorum?

Answer 11

origin: lateral epicondyle of humerus
insertion: extensor hoods of digits 2-5 (extensor hood: expansion of the extensor tendon as it passes over the dorsal aspect of the proximal phalange)
function: extends digits and wrist
innervation: radial nerve

Question 12

What is the origin, insertion, function, and innervation of the extensor digiti minimi?

Answer 12

origin: lateral epicondyle of humerus
insertion: extensor hood of 5th digit (little finger)
function: extends the 5th digit and wrist
innervation: radial nerve

Question 13

What is the origin, insertion, function, and innervation of the extensor carpi ulnaris?

Answer 13

origin: lateral epicondyle and posterior ulna
insertion: 5th metacarpal
function: extends and adducts the wrist
innervation: radial nerve

Question 14

What is the origin, insertion, function, and innervation of the supinator?

Answer 14

origin: lateral epicondyle of humerus, posterior ulna
insertion: proximal radius
function: supinates forearm at the radioulnar joints
innervation: radial neve

Question 15

What is the origin, insertion, function, and innervation of the abductor pollicis longus?

Answer 15

origin: posterior ulna, radius, interosseus membrane
insertion: base of 1st metacarpal
function: abducts and extends thumb
innervation: radial nerve

Question 16

What is the origin, insertion, function, and innervation of the extensor pollicis brevis?

Answer 16

origin: posterior radius, interosseus membrane
insertion: base proximal phalynx of thumb
function: extends thumb (does not extend DIP)
innervation: radial nerve

Question 17

What is the origin, insertion, function, and innervation of the extensor pollicis longus?

Answer 17

origin: posterior ulna, interosseus membrane
insertion: base of distal phalynx of thumb
function: extends thumb
innervation: radial nerve

Question 18

What is the origin, insertion, function, and innervation of the extensor indicis?

Answer 18

origin: ulna and interosseus membrane
insertion: extensor hood of the second digit (index finger)
function: extends index finger and wrist
innervation: radial nerve

Question 19

Identify these muscles of the posterior forearm. What layer are they in?

Answer 19

superficial layer

Question 20

Identify these muscles of the posterior forearm. What layer are they in?

Answer 20

superficial

Question 21

Identify these muscles of the posterior forearm. What layer are they in?

Answer 21

deep layer

Question 22

What is lateral epicondylitis? What muscle is most often affected? What movements of the arm are affected? What are common signs and symptoms?

Answer 22

is also known as tennis elbow. involves extensor muscles and tendons of the forearm that have origins on the lateral epicondyle. the tendon most commonly affected is that of extensor carpi radialis brevis (inserts on base of 3rd metacarpal) which helps stabilize the wrist when the elbow is extended. common signs and sx are pain with wrist extension against resistance, point tenderness or burning on lateral epicondyle, weak grip strength. sx are intensified with forearm activity

Question 23

Where do the posterior interosseus, anterior interosseus, and radial arteries travel in the forearm? What do they supply?

Answer 23

Note: The anterior and posterior interosseus arteries branch from the common interosseus artery which branches from the ulnar artery in the anterior forearm

posterior interosseus artery: contributes branches to the elbow joint and posterior compartment of the forearm

anterior interosseus artery: passes through anterior flexor compartment but has perforating branches that pass through the interosseus membrane to supply deep muscles of the posterior compartment in addition to supplying muscles in the anterior compartment

radial artery: contributes muscular branches to the extensor musculature on the radial side of the forearm as it courses toward the hand with the superficial branch of the radial nerve and is ultimately a primary source of blood supply to the thumb

Question 24

Identify these structures of the anterior and posterior forearm.

Answer 24

Question 25

What is the anatomical snuffbox? What are the boundaries of the anatomical snuffbox? What passes through it?

Answer 25

anatomical snuffbox is a term given to the triangular depression on the posterior-lateral side of the wrist (most evident with extension of thumb)

boundaries:

lateral: abductor pollicis longus and extensor pollicis brevis
medial: extensor pollicis longus
floor: scaphoid and trapezium, distal ends of extensor carpi radialis longus and brevis tendons

the radial artery passes through the anatomical snuffbox!

Question 26

How is the anatomical snuffbox clinically important?

Answer 26

the scaphoid may be palpated within the anatomical snuffbox to assess fracture of this bone after wrist injury. with a fracture accross the scaphoid, blood supply may be denied ot the proximal portion of the bone which could result in avascular necrosis. if disconnected from blood supply, would need surgical repair

Question 27

The tendons of flexor digitorum superificalis and profundus enter what kind of sheath? What about the flexor pollicis longus? What is this sheaths function?

Answer 27

They enter a common synovial flexor sheath and subsequently fan out to enter their respective digital synovial sheaths. These sheaths allow the tendons to slide freely over each other during movements of the fingers. Note that the flexor pollicis longus has its own synovial sheath

Question 28

What are fibrous digital sheaths? What is their function?

Answer 28

strong ligamentous tunnels that surround the tendons and their synovial sheaths and prevent the tendons from pulling away from the digits (bowstringing)

Question 29

What is tenosynovitis?

Answer 29

puncture wounds to the fingers can cause infections of the synvovial sheaths. the painful inflammation of the tendon is tenosynovitis. also, repetitive movements can cause inflammation of the tendons and sheats resulting in thickening of the fibrous sheaths and decreased ability to move the fingers

Question 30

Identify the portions of the extensor tendon.

Answer 30

Question 31

The tendons of the extensor digitorum and extensor pollicis longus pass onto the dorsal surface of the the and and expand over the proximal phlanges to form _____ ____.

Answer 31

extensor hoods

Question 32

Describe arterial supply to the dorsal surface of the hand.

Answer 32

The radial artery gives off a dorsal carpal branch which anastamoses with a branch of the ulnar artery to form the dorsal carpal artery/arch. The dorsal carpal arch gives rise to dorsal metacarpal arteries which ultimately divide to become dorsal digital arteries.

Question 33

Describe the venous supply in the dorsal hand.

Answer 33

Superficial and deep veins drain into a dorsal venous network on the back of the hand located over the metacarpal bones. Both cephalic and basilic veins originate from this dorsal venous network.

note that deep veins follow arteries in the hand.

Question 34

What nerves of the hand have these innervation patterns?

Answer 34

Question 35

What nerve of the hand has this innervation pattern? (be specific)

Answer 35