The posterior compartment of the forearm - muscles (dave's notes)

Question 1

List the 12 muscles of the posterior compartment of the forearm

Answer 1

Brachioradialis
Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor digitorum
Extensor digiti minimi
Extensor carpi ulnaris
Aconeus
Supinator
Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus
Extensor indicis

Question 2

What is the origin and insertion of brachioradialis?

Answer 2

Origin: The upper two thirds of the lateral supracondylar ridge of the humerus and lateral intermuscular septum
Insertion: Base of the styloid process of the radius

Question 3

What is the action and innervation of brachioradialis?

Answer 3

Flexes arm at the elbow and brings the forearm into the mid-prone position
Radial nerve.

Question 4

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

Answer 4

Origin: Lower 2/3rds lateral supracondylar ridge of humerus and lateral intermuscular septum
Insertion: Posterior base of 2nd metacarpal

Question 5

What is the action and innervation of extensor carpi radialis longus?

Answer 5

Extends and adducts the hand at the wrist

Posterior interosseous nerve

Question 6

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

Answer 6

Origin: Common extensor origin

Question 7

What is the common extensor origin?

What arises here?

Answer 7

The smooth area on the front of the lateral epicondyle 
The fused tendons of:
Extensor carpi radialis brevis
Extensor digitorum
Extensor digiti minimi
Extensor carpi ulnaris

Question 8

What is the action and innervation of extensor carpi radialis brevis?

Answer 8

Extends and adducts the hand at the wrist

Posterior interosseous nerve

Question 9

What is the origin and insertion of extensor digitorum?

Answer 9

Origin: CEO
Insertion: The extensor expansion of all four fingers, three and four normally fuse with fie only getting a slip

Question 10

What is the action and innervation of extensor digitorum?

Answer 10

Extends all joints of fingers

Posterior interosseous nerve

Question 11

What is the origin and insertion of extensor digiti minimi?

Answer 11

Origin: CEO
Insertion: Extensor expansion of the little finger, usually two tendons which are joined by extensor digitorum

Question 12

What is the innervation and action of extensor digiti minimi?

Answer 12

Extends all the joints of the little finger.

Posterior interosseous nerve

Question 13

What is the origin and insertion of extensor carpi ulnaris?

Answer 13

Origin: CEO and aponeurotic sheath from the ulna
Insertion: BASE of the 5th ??? via a groove by ulnar styloid

Question 14

What is the action and innervation of extensor carpi ulnaris?

Answer 14

Extends and adducts the hand at the wrist

Posterior interosseous nerve

Question 15

What is the origin and insertion of aconeus?

Answer 15

Origin: Smooth surface at the lower extremity of posterior aspect of the lateral epicondyle of humerus
Insertion: Lateral side of olecranon

Question 16

What is the action and innervation of aconeus?

Answer 16

Weak extensor of the elbow

RADIAL nerve

Question 17

What is the origin and insertion of supinator?

Answer 17

Origin: Deep part from the supinator crest and fossa of the ulna.
Superficial part from the lateral epicondyle and lateral ligament of the elbow and annular ligament
Insertion: Neck and shaft of the radius

Question 18

What is the action and innervation of supinator?

Answer 18

Supinates the forearm.

Posterior interosseous nerve

Question 19

When does supinator act independently?

Answer 19

When the elbow is extended

Question 20

What is the origin and insertion of abductor pollicis longus?

Answer 20

Origin: The upper posterior surface of the ulna and middle 1/3rd of the posterior surface of the radius and interosseus membrane.
Insertion: Over the tendons of the radial extensors and brachioradialis to the base of the first metacarpal and trapezium

Question 21

What is the action and innervation of abductor pollicis longus?

Answer 21

Abducts and extends the thumb at the carpometacarpal joint

Posterior interosseous nerve

Question 22

What is the origin and insertion of extensor pollicis brevis?

Answer 22

Origin: Lower 1/3 of the posterior shaft of the radius and interosseous membrane
Insertion: Over the tendons of the radial extensor and brachioradialis to the base of the proximal phalanx

Question 23

What is the action and innervation of extensor pollicis brevis?

Answer 23

Extends the metacarpophalangeal joints of the thumb

Posterior interosseous nerve

Question 24

What forms the radial side of the anatomical snuff box?

Answer 24

Abductor pollicis brevis and extensor pollicis brevis

Question 25

What forms the ulnar side of the anatomical snuff box?

Answer 25

Extensor pollicis longus

Question 26

What is the origin and insertion of extensor pollicis longus?

Answer 26

Origin: The middle 1/3rd of the posterior ulna and interosseous membrane
Insertion: Base of the distal phalanx of the thumb

Question 27

What is the action and innervation of extensor pollicis longus?

Answer 27

Extends the IP and MCP joints of the thumb

Posterior interosseous nerve

Question 28

What is the origin and insertion of extensor indicis?

Answer 28

Origin: The lower posterior shaft of the ulnar and interosseous membrane
Insertion: The extensor expansion of the index finger

Question 29

What is the action and innervation of extensor indicis?

Answer 29

Extends all the joints of the index finger

Posterior interosseous nerve