Muscles of the posterior compartment of the forearm

Question 1

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

Answer 1

Brachioradialis, extensor carpi radialis longus and brevis, extensor digitorum, extensor digit minimi, extensor carpi ulnaris, anconeus.

Question 2

Why is the brachioradialis a paradoxical muscle?

Answer 2

It’s origin and innervation are characteristic of an extensor muscle, but it is actually a flexor muscle at the elbow.

Question 3

When is the brachioradialis most visible?

Answer 3

Forearm half pronated and flexing at the elbow against resistance.

Question 4

Brachioradialis attachments

Answer 4

Origionates from the proximal aspect of the lateral supracondylar ridge of humerus, and attaches to the distal end of the radius, just before the radialstyloid process.

Question 5

Brachioradialis actions

Answer 5

Flexes at the elbow

Question 6

Brachioraialis innervation

Answer 6

Radial nerve

Question 7

Extensor carpi radialis longus and brevis attachments

Answer 7

The ECRL origionates from the supracondylar ridge, while the ECRB origionaes from the lateral epicondyle. Their tendons attach to metacarpals II and III.

Question 8

Extensor carpi radialis longus and brevis actions

Answer 8

Extends and abducts the wrist

Question 9

Extensor carpi radialis longus and brevis innervation

Answer 9

Radial nerve

Question 10

Extensor digitorum attachments

Answer 10

Origionates from the lateral epicondyle. The tendon continues into the distal part of the forearm, where it splits into four and inserts into the extenor hood of each finger.

Question 11

Extensor digitorum actions

Answer 11

Extends the medial four fingers and the MCP and IP joints

Question 12

Extensor digitorum innervation

Answer 12

Deep branch of the radial nerve

Question 13

Extensor digit minimi attachments

Answer 13

Origionates from the lateral epicondyle of the humerus. It attaches, with the extensor digitorum tendon, into the extensor hood of the little finger.

Question 14

Extensor digit minimi actions

Answer 14

Extends the little finger and contributes to extension at the wrist.

Question 15

Extension digit minimi innervation

Answer 15

Deep branch of the radial nerve

Question 16

Extensor carpi ulnaris attchments

Answer 16

Origionates from the lateral epicondyle of the humerus, and attaches to the base of metacrpal V.

Question 17

Extensor carpi ulnaris actions

Answer 17

Extension and adduction of the wrist

Question 18

Extensor carpi ulnaris innervation

Answer 18

Deep branch of radial nerve

Question 19

Anconeus attachments

Answer 19

Origionates from the lateral epicondyle, and attaches to the posterior and lateral part of the olecranon.

Question 20

Anconeus actions

Answer 20

Extends and stabilises the elbow joint. Abducts the ulna during pronation of the forearm.

Question 21

Anconeus innervation

Answer 21

Radial nerve

Question 22

What are the deep muscles of the posterior forearm?

Answer 22

Supinator, abductor pollicus longus, extensor pollicus brevis, extensor pollicus longus and extensor indicis proprius.

Question 23

Supinator attachments

Answer 23

It has two heads of origin. One origionates from the lateral epicondyle of the humerus, the other from the posterior surface of the ulna. They insert together into the posterior surface of the radius.

Question 24

Supinator actions

Answer 24

Supinates the forearm

Question 25

Supinator innervation

Answer 25

Deep branch of radial nerve

Question 26

Abductor pollicus longus attachments

Answer 26

Origionates from the interosseous membrane and the adjacent posterior surfaces of the radius and ulna. It attaches to the lateral side of the base of metacaroal I.

Question 27

Abductor pollicus longus actions

Answer 27

Abducts the thumb

Question 28

Abductor pollicus longus innervation

Answer 28

Posterior interosseous branch of the radial nerve

Question 29

Extensor pollicus brevis attachments

Answer 29

Origionates from the posterior surface of the radius and interosseus membrane. It attaches to the base of the proximal phalanx of the thumb.

Question 30

Extensor pollicus brevis actions

Answer 30

Extends the metacarpophalangeal and carpometacarpal joints of the thumb

Question 31

Extensor pollicus brevis innervation

Answer 31

Posterior interosseous branch of the radial nerve

Question 32

Extensor pollicus longus surface marking

Answer 32

The tendon of the extensor pollicus longus forms the medial border of the anatoical snuffbox.

Question 33

Extensor pollicus longus attachments

Answer 33

Origionates from the posterior surface of the ulna and interosseous membrane. It attaches to the distal phalynx of the thumb.

Question 34

Extesor pollicus longus actions

Answer 34

Extends all jonts of the thmb: carpometacarpal, metacarpophalangeal and interphalangeal.

Question 35

Extensor pollicus longus innervation

Answer 35

Poterior interosseous branch of the radial nerve

Question 36

Extensor indicis proprius attachments

Answer 36

Origionates from the posterior surface of the ulna and interosseous membrane, distal to the extensor pollicus longus. Attaches to the extenosr hood of the index finger.

Question 37

Extensor indicis proprius actions

Answer 37

Extends the index finger

Question 38

Extensor indicis proprius innervation

Answer 38

Posterior interosseous branch of the radial nerve