Posterior Forearm Muscles (Quiz 2/Exam 2) Flashcards
The extensor muscles are on the __________________________ compartment of the forearm
posterior (extensor-supinator)
The extensor muscles are on the posterior (extensor-supinator) compartment of the forearm. They are all innervated by branches of the….
radial n.
The extensor muscles are on the posterior (extensor-supinator) compartment of the forearm. What are the 3 functional groups?
1) muscles that extend and abduct or adduct the hand at the wrist joint
2) muscles that extend the medial 4 fingers
3) muscles that extend or abduct the thumb
What are the 3 muscles that extend and abduct or adduct the hand at the wrist joint?
1) extensor carpi radialis longus
2) extensor carpi radialis brevis
3) extensor carpi ulnaris
What are the 3 muscles that extend the medial 4 fingers?
1) extensor digitorum
2) extensor indicis
3) extensor digiti minimi
What are the 3 muscles that extend or abduct the thumb?
1) abductor pollicis longus
2) extensor pollicis brevis
3) extensor pollicis longus
What are the 6 superficial extensors?
1) extensor carpi radialis brevis
2) extensor digitorum
3) extensor digit minimi
4) extensor carpi ulnaris
5) brachioradialis
6) extensor carpi radialis longus
4 of the superficial extensors
1) extensor carpi radialis brevis
2) extensor digitorum
3) extensor digit minimi
4) extensor carpi ulnaris
are all attached proximally by a common extensor tendon to the __________ epicondyle
lateral
The proximal attachment of the brachioradialis and extensor carpi radialis longus is to the lateral ________________ ridge of the humerus and adjacent lateral inter-muscular system
supraepicondylar
What is the origin/proximal attachment of the brachioradialis?
proximal 2/3 of supra-epicondylar ridge of humerus
What is the insertion/distal attachment of the brachioradialis?
lateral surface of distal end of radius proximal to styloid process
What innervates the brachioradialis?
radial n.
What are the actions of the brachioradialis?
relatively weak flexion of forearm (maximal when forearm is mid-pronated, aka thumb facing ceiling/perpendicular to ceiling)
The _________________ and the ______________ are the only muscles of the posterior forearm compartment that do not cross and therefore are incapable of acting at the wrist
brachioradialis, supinator
What is the origin/proximal attachment for the extensor carpi radialis longus (ECRAL)?
lateral supra-epicondylar ridge of humerus
What is the insertion/distal attachment of the extensor carpi radialis longus (ECRAL)?
dorsal aspect of base of 2nd metacarpal
What innervates the extensor carpi radialis longus (ECRAL)?
deep branch of the radial n.
What are the actions of the extensor carpi radialis longus (ECRAL)?
-extend and abduct the arm at wrist joint
-extensor carpi radialis longus (ECRAL) is active during fist clenching
What is the origin/proximal attachment of the extensor carpi radialis brevis (ECRB)?
lateral epicondyle of the humerus (common extensor origin)
What is the insertion/distal attachment of the extensor carpi radialis brevis (ECRB)?
dorsal aspect of base of the 3rd metacarpal
What innervates the extensor carpi radialis brevis (ECRB)?
deep branch of the radial n.
What are the actions of the extensor carpi radialis brevis (ECRB)?
-extend and abduct the hand at the wrist joint
-extensor carpi radialis brevis (ECRB) is active during fist clenching
What is the origin/proximal attachment for the extensor digitorum?
lateral epicondyle of humerus (common extensor origin)
What is the insertion/distal attachment of the extensor digitorum?
extensor expansions of medial 4 digits (sides of fingers)
What innervates the extensor digitorum?
deep branch of the radial n.
What are the actions of the extensor digitorum?
extends medial 4 digits primarily at the metacarpophalangeal (MCP) joints, secondarily as interphalangeal (IP) joints
What is the origin/proximal attachment of the extensor digiti minimi?
lateral epicondyle of the humerus (common extensor origin)
What is the insertion/distal attachment of the extensor digiti minimi?
extensor expansion of 5th digit
What innervates the extensor digiti minimi?
deep branch of radial n.
What are the actions of the extensor digit minimi?
extends 5th digit primarily at MCP joint and secondarily at IP joint
What are the origins/proximal attachments for the extensor carpi ulnaris (ECU)?
-lateral epicondyle of humerus
-posterior border of ulna via a shared aponeurosis
What is the insertion/distal attachment for the extensor carpi ulnaris (ECU)?
dorsal aspect of the base of the 5th metacarpal
What innervates the extensor carpi ulnaris (ECU)?
deep branch of radial n.
What are the actions of the extensor carpi ulnaris (ECU)?
-extends and adducts the hand at wrist joint
-active during fist clenching
Which muscles are active during fist clenching?
-extensor carpi radialis longus
-extensor carpi radialis brevis
-extensor carpi ulnaris
What muscles have distal attachments to the metacarpals?
TEST Q
1st metacarpal) abductor pollicis longus
2nd) extensor carpi radialis longus
3rd) extensor carpi radialis brevis
4th) nothing
5th) extensor carpi ulnaris
What muscles have attachments to digit expansions?
TEST Q
1st expansion) extensor digitorum (medial 4 digit expansions)
2nd) extensor indicis
3rd) nothing
4th) nothing
5th) extensor digit minini
What are the origins/proximal attachments of the supinator?
-lateral epicondyle of the humerus
-radial collateral and anular ligaments
-supinator fossa
-crest of ulna
What are the insertions/distal attachments for the supinator?
lateral, posterior, and anterior surfaces of the proximal 3rd of radius
What innervates the supinator?
deep branch of radial n.
What are the actions of the supinator?
-supinates forearm
-rotates radius to turn palm anteriorly or superiorly (if elbow is flexed)
What is the origin/proximal attachment for the extensor indicis?
posterior surface of distal 3rd of ulna and interosseous membrane
What is the insertion/distal attachment of the extensor indicis?
extensor expansion of 2nd digit
What innervates the extensor indicis?
deep branch of radial n.
What are the actions of the extensor indicis?
-extends 2nd digit (enabling its independent extension)
-helps extend hand at the wrist
What is the origin/proximal attachment of the abductor pollicis longus?
posterior surface of the proximal halves of the ulna, radius, and interosseous membrane
What is the insertion/distal attachment of the abductor pollicis longus?
base of 1st metacarpal
What innervates the abductor pollicis longus?
deep branch of the radial n.
What is the action of the abductor pollicis longus?
abducts thumb and extends it at the CMC joint
What is the origin/proximal attachment of the extensor pollicis longus?
posterior surface of the middle 3rd of ulna and interosseous membrane
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What is the insertion/distal attachment of the extensor pollicis longus?
dorsal aspect of the base of the distal phalanx of the thumb
What innervates the extensor pollicis longus?
deep branch of the radial n.
What are the actions of the extensor pollicis longus?
-extends distal phalanx of thumb at IP joint
-extends MCP and CMC joints
What is the origin/proximal attachment for the extensor pollicis brevis?
posterior surface of the distal 3rd of the radius and interosseous membrane
rrrrrrrrrrrrrrradius = brrrrrrrrevis
What is the insertion/distal attachment of the extensor pollicus brevis?
dorsal aspect of the base of the proximal phalanx of the thumb
What innervates the extensor pollicis brevis?
deep branch of the radial n.
What are the actions of the extensor pollicis brevis?
-extends proximal phalanx at thumb at the MCP joint
-extends CMC joint
When can you see the anatomical snuff box?
when thumb is abducted
What is the medial boundary of the anatomical snuffbox?
test q
extensor pollicis brevis
What is the lateral boundary of the anatomical snuffbox?
test q
extensor pollicis longus and abductor pollicis longus
What is the floor of the anatomical snuffbox?
scaphoid and trapezium
What artery is within the anatomical snuffbox?
radial a.
