KIN 100 MUSCLES OF THE POSTERIOR FOREARM

what are the superficial muscles of the posterior forearm?

1. brachioradialis

2. extensor carpi radialis longus

3. extensor carpi radialis brevis

4. extensor digitorum

5. extensor digiti minimi

6. extensor carpi ulnaris

what are the deep muscles of the posterior forearm?

7. supinator

8. extensor indicis

what are the outcropping muscles of the posterior forearm?

9. abductor pollicis longus

10. extensor pollicis longus

11. extensor pollicis brevis

brachioradialis (layer/classification, prox, distal, innervation, actions)

layer: superficial

prox: lateral supraepicondylar ridge of humerus

distal: distal radius (does not cross the wrist)

innervation: radial nerve

actions: elbow flexion (in a semi-prone position)

extensor carpi radialis longus

• layer: superficial

• prox: lateral supraepicondylar ridge of humerus

• distal: base of 2nd metacarpal

• innervation: radial nerve

• actions: wrist extension, wrist abduction

extensor carpi radialis brevis

• layer: superficial

• prox: common extensor origin

• distal: base of 3rd metacarpal

• innervation: deep branch of radial nerve

• actions: wrist extension, wrist abduction

extensor digitorum

• layer: superficial

• prox: common extensor origin

• distal: distal phalanges of digits 2-5 via extensor expansions

• innervation: deep branch of radial nerve

• actions: wrist extension, extension of all joints for digits 2-5

label this diagram of the superficial layer of muscles of the posterior forearm

1. brachioradialis

2. extensor carpi radialis longus

3. extensor carpi radialis brevis

4. extensor digitorum

what happens to the tendons of the extensor digitorum?

• they flatten out, to form the extensor expansions, which are located on the dorsal aspect of the metacarpals and phalanges of digits 2-5

what shape is each extensor expansion? and what else can it be referred to as?

• they are triangular-shaped

• they can be referred to as the dorsal expansion or “hood”

how many bands does the tendon of extensor digitorum divide into? what are they, and where do they insert onto?

3 bands: 1 median band, and 2 lateral bands.

median: middle phalanx

lateral: distal phalanx

label this diagram of the extensor expansions

1. tensor hood

2. median band

3. lateral bands

extensor digiti minimi

• layer: superficial

• prox: common extensor origin

• distal: distal phalanx of digit 5 via extensor expansion

• innervation: deep branch of radial nerve

• actions: wrist extension, extension of all joints for digit 5

extensor carpi ulnaris

• layer: superficial

• prox: common extensor origin

• distal: base of 5th metacarpal

• innervation: deep branch of radial nerve

• actions: wrist extension, wrist adduction

label this diagram of the superficial layers of the posterior forearm

1. extensor digiti minimi

2. extensor carpi ulnaris

supinator

• deep layer

• prox: common extensor origin and supinator crest of ulna

• distal: proximal third of radius

• innervation: deep branch of radial nerve

• action: forearm supination

extensor indicis

• layer: deep

• prox: interosseous membrane and ulna

• distal: distal phalanx of 2nd digit via extensor expansion (tendon connects into extensor expansion onto the dorsum of the 2nd digit. it can act on allll joints of the 2nd digit)

• innervation: deep branch of radial nerve

• actions: extension of all joints in joint 2

abductor pollicis longus (APL)

• outcropping muscle

• prox: interosseous membrane

• distal: base of 1st metacarpal

• innervation: deep branch of radial nerve

• actions: thumb abduction, and thumb extension

extensor pollicis brevis (EPB)

• layer: outcropping muscle

• prox: interosseous membrane

• distal: proximal phalanx of thumb

• innervation: deep branch of radial nerve

• actions: extension of all jionts of the thumb EXCEPT interphalangeal

extensor pollicis longus (EPL)

• layer: outcropping muscle

• prox: interosseous membrane

• distal: distal phalanx of thumb

• innervation: deep branch of radial nerve

• actions: extension of all joints of the thumb

label this diagram of the deep layer of the posterior forearm

1. supinator

2. extensor indicis

3. abductor pollicis longus

4. extensor pollicis brevis

5. extensor pollicis longus

what is the anatomical snuff box

• a hollow space thats formed between the tendons of the EPL (medially) and the APL & EPB (laterally)

what does the floor of the snuff box consist of?

• the scaphoid and trapezium

what artery passes through the anatomical snuff box?

• the radial artery

what nerve passes through the snuff box? and at what capacity

• the superficial branch of the radial nerve

• found SUPERFICIALLY

label this diagram of the anatomical snuffbox

1. extensor pollicis longus

2. extensory pollicis brevis

3. abductor pollicis longus

4. radial artery

5. superficial radial nerve

label this diagram of the dorsum of the wrist

1. ulna

2. radius

3. dorsal tubercle of the radius

4. abductor pollicis longus

5. extensor pollicis brevis

6. extensor carpi radialis longus

7. extensor carpi radialis brevis

8. extensor pollicis longus

9. extensor digitorum

10. extensor digiti minimi

11. extensor carpi ulnaris

what muscles of the posterior forearm flex the elbow?

1. brachioradialis (in a semi-prone position)

which muscles of the posterior forearm extend the wrist?

• extensor carpi radialis longus

• extensor carpi radialis brevis

• extensor digitorum

• extensor digiti minimi

• extensor carpi ulnaris

what muscles of the posterior forearm abduct the wrist?

• extensor carpi radialis longus

• extensor carpi radialis brevis

*bcz wrist abduction is radial deviation!! so if it says radialis, its abduction!!

what muscles of the posterior forearm adduct the wrist?

• extensor carpi ulnaris

which muscles of the posterior forearm extend the joints of the wrist and hand and at what capacities?

• extensor digitorum (extension of all joints for digits 2-5)

• extensor digiti minimi (extension of all joints of digit 5)

• extensor indicis (extends all joints in digit 2) (indicis = index finger = digit 2)

• abductor pollicis longus (extends the thumb)

• extensor pollicis brevis (extends all joints of the thumb except interphalangeal)

• extensor pollicis longus (extends all joints of the thumb, including interphalangeal)

which muscles of the posterior forearm abduct the thumb?

• abductor pollicis longus (APL)

which muscles of the posterior forearm extend the thumb?

• abductor pollicis longus (APL)

• extensor pollicis brevis (EPB) (all joints of the thumb except interphalangeal joints)

• extensor pollicis longus (EPL) (all joints of the thumb)

which muscles of the posterior forearm supinate the forearm? which muscle of the arm helps?

• supinator

• arm: biceps brachii