L9: Cubital fossa and Musculo-neuro-vascular systems of the posterior forearm

Question 1

cubital fossa; boundaries

Answer 1

triangular region anterior to elbow joint

Boundaries:
superior: imaginary line between medial and lateral epicondyles
medial: pronator teres (lateral border)
lateral: brachioradialis (medial border)
roof: fascia of forearm + bicipital aponeurosis
floor: overlies elbow joint capsule: biceps tendon [superficial], brachialis [deep], supinator [deep]

Question 2

contents of cubital fossa

Answer 2

from lateral to medial
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Radial Nerve
Biceps Tendon
Brachial Artery
Median Nerve

Question 3

extensor retinaculum

Answer 3

Similar to flexor retinaculum except located on dorsum of wrist
Extensor muscle tendons pass under it as they make their way to the hand
Prevents bowstringingof extensor tendons during wrist extension
Extensor tendons covered in synovial sheaths as they pass under retinaculum. Reduces friction during movement

Question 4

posterior compartment of forearm (11)
> superficial muscles (6)

Answer 4

• brachioradialis
• extensor carpi radialis longus
• extensor carpi radialis brevis
• extensor carpi ulnaris
• extensor digitorum
• extensor digiti minimi

Question 5

posterior compartment (11)
> deep muscles (5)

Answer 5

• supinator
• abductor pollicis longus
• extensor pollicis brevis
• extensor pollicis longus
• extensor indicis

Question 6

• general rule*
  posterior forearm innervation

Answer 6

posterior forer]arm muscles supplied by the posterior interosseous branch of the radial nerve
EXCEPT
- brachioradialis > supplied by radial nerve directly
- Extensor carpi radialis longus > supplied by radial nerve directly

Question 7

general rule:
superficial muscles of posterior compartment

Answer 7

superficial muscles of posterior compartment are attached to the lateral epicondyle through the common extensor tendon

Question 8

brachioradialis; origin + insertion

Answer 8

origin: proximal 2/3 of lateral supracondylar ridge

insertion: lateral surface of distal end of radius and styloid process

Question 9

brachioradialis; innervation + actions

Answer 9

innervation: radial nerve directly

actions: when forearm is pronated, BR supinates forearm and flexes elbow. When forearm is supinated, BR pronates forearm

Question 10

extensor carpi radialis longus; origin + insertion

Answer 10

origin: lateral supracondylar ridge

insertion: dorsal aspect of base of 2nd metacarpal

Question 11

extensor carpi radialis longus; innervation + actions

Answer 11

innervation: radial nerve directly

actions: extends & abducts wrist at radiocarpal joint

Question 12

extensor carpi radialis brevis; origin + insertion

Answer 12

origin: lateral epicondyle (common extensor origin)

insertion: dorsal aspect of base of 3rd metacarpal

Question 13

extensor carpi radialis brevis; innervation + actions

Answer 13

innervation: posterior interosseous branch of radial nerve

actions: extends and abducts wrist at radiocarpal joint

Question 14

extensor carpi ulnaris; origin + insertion

Answer 14

origin: lateral epicondyle (common extensor origin)

insertion: dorsal aspect of base of 5th metacarpal

Question 15

extensor carpi ulnaris; innervation + actions

Answer 15

innervation: posterior interosseous branch of radial nerve

actions: extends & adducts wrist at radiocarpal joint

Question 16

extensor digitorum; origin + insertion

Answer 16

origin: common extensor origin

insertion: dorsal aspect of base of middle and distal phalanges 2-5 [as a large extensor expansion]

Question 17

extensor digitorum; innervation + actions

Answer 17

innervation: posterior interosseous branch of radial nerve

actions: extends digits 2-5 at proximal & distal interphalangeal joints. Extends wrist [radiocarpal joint]

Question 18

tendons of extensor digitorum

Answer 18

Form an extensor expanse3 bands unite all 4 tendons over dorsal aspect of digits 2-5, proximal to the MCP joints (knuckles)
Restricts independent action of fingers
A single finger can remain fully flexed while 1 other is fully extended.
Fully flex your index finger, fully extend your little finger. Now try to fully flex or extend your other 2 fingersNote that you can’t! This is due to the intertendinous connections of the extensor expanse

Question 19

insertions of extensor digitorum

Answer 19

At the distal end of the extensor digitorum tendons, the tendon flattens and forms an extensor expansion which has 3 bands
1 median band
*The median slip inserts into the dorsal aspect of the middle phalanx
2 outer bands
*The 2 outer slips reunite on the dorsal aspect of the distal phalanx
The proximal extensor expansion also inserts into the underlying MCP joint capsule

Question 20

extensor digiti minimi; origin + insertion

Answer 20

origin: common extensor origin

insertion: dorsal aspect of digit 5, base of middle and distal phalanx

Question 21

extensor digiti minimi; innervation + actions

Answer 21

innervation: posterior interosseous branch of radial nerve

actions: extends little finger at distal and proximal interphalangeal joints

Question 22

supinator; origin + insertion

Answer 22

origin:
- deep head: supinator crest of ulna
- superficial head: common extensor tendon

Question 23

supinator; innervation + actions

Answer 23

innervation: posterior interosseous branch of radial nerve

actions: supinates forearm

Question 24

abductor pollicis longus; origin + insertion

Answer 24

origin: posterior ulna, interosseous membrane & ulna

insertion: lateral aspect of base of 1st metacarpal

Question 25

abductor pollicis longus; innervation + actions

Answer 25

innervation: posterior interosseous branch of radial nerve

actions: extends & abducts thumb at CMC joint

Question 26

extensor pollicis longus; origin + insertion

Answer 26

origin: posterior surface of middle third ulna and interosseous membrane

insertion: dorsal aspect of base of thumb distal phalanx

Question 27

extensor pollicis longus; innervation + actions

Answer 27

innervation: posterior interosseous branch of radial nerve

actions: extends proximal and distal phalanges of thumb. Extends 1st MC joint

Question 28

extensor pollicis brevis; origin + insertion

Answer 28

origin: posterior surface of distal radius and interosseous membrane

insertion: dorsal aspect of base of proximal phalanx of thumb

Question 29

extensor pollicis brevis; innervation + actions

Answer 29

innervation: posterior interosseous branch of radial nerve

actions: extends proximal phalanx of thumb. Extends 1st MC joint

Question 30

extensor indices; origin + insertion

Answer 30

origin: posterior surface of ulna and interosseous membrane

insertion: dorsal aspect of index finger (extensor expansion)

Question 31

extensor indices; innervation + actions

Answer 31

innervation: posterior interosseous branch of radial nerve

actions: extends index finger

Question 32

arterial supply to forearm

Answer 32

As brachial artery enters forearm deep to bicipital aponeurosis it bifurcates:
*Radial artery
*Ulnar arteryElbow joint supply: (anastomotic network)
*Superior and inferior ulnar collateral arteries anastomose with ulnar recurrent arteries
*Radial collateral artery anastomoses with radial recurrent arteries

Question 33

forearm nerves

Answer 33

• median nerve and anterior interosseous branch
• ulnar nerve
• radial nerve and posterior interosseous branch