UNIT 1: extensor muscles of arm/forearm

Question 1

which nerve innervates the extensor muscles?

Answer 1

radial nerve

Question 2

which muscles extend, abduct/adduct wrist?

Answer 2

• extensor carpi radialis brevis
• extensor carpi radialis longus
• extensor carpi ulnaris

Question 3

which muscles extend medial 4 digits?

Answer 3

• extensor digitorum
• extensor digiti minimi
• extensor indicis

Question 4

which muscles extend thumb?

Answer 4

• abductor pollicis longus
• extensor pollicis brevis
• extensor pollicis longus

Question 5

what is the difference between the main action of extensor pollicis brevis and longus?

Answer 5

brevis- extends proximal phalanx at metacarpophalangeal joint
longus - extends distal phalanx at interphalangeal joint

Question 6

how are the superficial extensor muscles split?

Answer 6

• proximal attachment to lateral epicondyle by common extensor
• proximal attachment to lateral supraepicondylar ridge of humerus

Question 7

Which muscles have proximal attachment to lateral epicondyle by common extensor?

Answer 7

• extensor carpi radialis brevis
• extensor digitorum
• extensor digiti minimi
• extensor carpi ulnaris

Question 8

Which muscles have proximal attachment to lateral supraepicondylar ridge of humerus?

Answer 8

• extensor carpi radialis brevis

- brachoradialis

Question 9

which muscles are classified as deep extensor?

Answer 9

• abductor pollicis longus
• extensor pollicis brevis
• extensor pollicis longus

Question 10

what is the role of the extensor retinaculum?

Answer 10

tendons converge at wrist

- prevents bowstring of tendons

Question 11

what are the tendons at the wrist covered with?

Answer 11

synovial tendon sheaths - reduce friction

Question 12

how are adjacent tendons of extensor digitorum linked? and what does this result in?

Answer 12

linked proximal to metacarpophalangeal joint by three intertendinous connections
- resists independent extension of finger so no finger can remain fully flexed as another extends

Question 13

what is the extensor muscle of the arm?

Answer 13

triceps brachii

Question 14

what are three sections of the triceps and where do they insert?

Answer 14

• long head = infraglenoid tubercle of scapula
• lateral head/ medial head = posterior surface of humerus
• all three heads converge on olecranon of humerus

Question 15

what action does the triceps do?

Answer 15

extends the elbow joint

Question 16

what additional action does the long head of triceps?

Answer 16

extend and adduct arm at shoulder joint

Question 17

what is the role of the anconeus?

Answer 17

• minor elbow extensor

- assists triceps in extending elbow joint and abducting ulna in pronation of forearm

Question 18

which structures form the borders of the anatomical snuffbox?

Answer 18

• medial: extensor pollicis longus
• lateral: extensor pollicis brevis/ abductor pollicis longus
• floor: scaphoid and trapezium
• roof: skin