Posterior compartment of forearm - extensor

Question 1

Where do most muscles of post. compartment of forearm originate from?

Answer 1

common extensor origin - lateral epicondyle of humerus

Question 2

What are the SUPERFICIAL muscles of the posterior compartment of forearm?

Answer 2

brachioradialis
extensor carpi radialis longus 
extensor carpi radialis brevis
extensor digitorum communis
extensor digiti minimi
extensor carpi ulnaris
anconeus

Question 3

What are the attachments and actions of brachioradialis?

Answer 3

origin: upper 2/3 of lateral supracondylar ridge of humerus
insert: styloid process of radius
actions: weak elbow flexor: force directed here is translational - force is directed onto forearm to enhance stability at elbow joint

Question 4

What are the attachments and actions of extensor carpi radialis longus?

Answer 4

Origin: lateral 1/3 of supracondylar ridge of humerus
Insert: 2nd metacarpal
actions: wrist extension, radial deviation

Question 5

What are the attachments and actions of extensor carpi radialis brevis?

Answer 5

origin: CEO
Insert: 3rd metacarpal
actions: wrist extension, radial deviation

Question 6

What is the primary action or extensor carpi radialis longus and brevis?

Answer 6

oppose wrist flexion

Question 7

What are the attachments and actions of extensor digitorum communis?

Answer 7

origin: CEO, intermuscular septa
insert: 2-5 digits
actions: extend MCP, IP joints and wrist

Question 8

What are the attachments and actions of extensor digiti minimi?

Answer 8

origin: CEO, IS
insert: 5th digit
action: extend little finger, weak extensor of wrist

Question 9

What are the attachments and actions of extensor carpi ulnaris?

Answer 9

origin: CEO, ulna
insert: 5th metacarpal
action: wrist extension, ulnar deviation
BUT primary role: oppose wrist flexion

Question 10

What are the attachments and actions of anconeus?

Answer 10

origin: posterior aspect of lateral epicondyle of humerus
insert: lateral aspect of ulna in olecranon fossa
actions: ulnar rotation, abducts ulnar in pronation, stabilise elbow joint

Question 11

What is the nerve supply of extensor compartment of forearm?

Answer 11

Radial nerve

Question 12

What are the DEEP muscles of extensor compartment of forearm?

Answer 12

supinator
abductor pollicis longus (thumbside)
extensor pollicis longus
extensor pollicis brevis
extensor indicis (index finger)

Question 13

What are the attachments and actions of supinator?

Answer 13

Origin: CEO, radial collateral ligament of elbow
Insert: anterior aspect of radius - proximal 1/3
actions: supination of forearm when elbow is extended + biceps brachii when elbow is flexed 90 degrees

Question 14

What are the attachments and actions of abductor pollicis longus?

Answer 14

origin: middle third of shaft of radius, upper third of post. shaft of ulna, IO membrane
insert: 1st metacarpal
action: abduct thumb, extend thumb, radial deviation of hand

Question 15

What are the attachments and actions of extensor pollicis brevis?

Answer 15

origin: radius, IO membrane
insert: proximal phalanx of thumb
action: extend thumb at MCP joint, abduction of thumb

Question 16

What are the attachments and actions of extensor pollicis longus?

Answer 16

origin: ulna, IO membrane
insert: distal phalanx of thumb
action: adducts thumb, extends thumb at MCP joint

Question 17

What are the attachments and actions of extensor indicis?

Answer 17

origin: distal third of post. shaft of radius, IO membrane
insert: 2nd digit
action: extend index finger, extends wrist (with help of extensor digitorum communis)