L8: Musculo-neuro-vascular systems of the arm and anterior compartment of the forearm

Question 1

compartments of forearm

Answer 1

similar to arm, forearm is surrounded by a layer of fascia called antebrachial fascia
> is continuous with brachial fascia proximally and fascia of the hand distally

forearm us divided into 2 compartments by:
-medial intermuscular septum
-ulna
-interosseous membrane
-radius
-lateral intermuscular septum

Question 2

compartment syndrome

Answer 2

excessive swelling or bleeding within a compartment
usually after an injury

exerts pressure on anything within that compartment - nerves, muscles, arteries and veins

can cause irreversible damage to all tissues in compartment

treated with emergency fasciotomy

Question 3

anterior compartment (8) of forearm;
> superficial muscles (5)

Answer 3

pronator teres
flexor carpi radialis
palmaris longus
flexor carpi ulnaris
flexor digitorum superficialis

Question 4

anterior compartment (8) of forearm
> deep muscles (3)

Answer 4

flexor pollicis longus
flexor digitorum profundus
pronator quadratus

Question 5

general rule
anterior forearm supplied by

Answer 5

anterior forearm muscles supplied by the median nerve:
-either directly
- or by anterior interosseous nerve (a branch of median nerve)
EXCEPT:
- flexor carpi ulnaris > ulnar nerve
- ulnar 1/2 of flexor digitorum profundus > ulnar nerve

Question 6

pronator teres; origin + insertion

Answer 6

origin:
-medial epicondyle of humerus
-coronoid process of ulna

insertion:
- anterior surface of radial mid-shaft

Question 7

pronator teres; innervation + actions

Answer 7

innervation: median nerve

actions: pronates forearm at radioulnar joint, weak flexor of elbow joint

Question 8

Flexor carpi radialis; origin + insertion

Answer 8

origin:
- medial epicondyle of humerus

insertion:
- palmar surface of base of metacarpals 2 and 3

Question 9

Flexor carpi radialis; innervation + actions

Answer 9

innervation: median nerve

actions: flexes wrist (radiocarpal) joint, weak radial deviation of wrist

Question 10

palmaris longus; origin + insertion

Answer 10

origin:
- median epicondyle of humerus

insertion:
- flexor retinaculum
- palmar aponeurosis

Question 11

palmaris longus; innervation + actions

Answer 11

innervation: median nerve

actions: flexes hand at wrist (radiocarpal) joint, tightens palmar aponeurosis when gripping

Question 12

flexor carpi ulnaris; origin + insertion

Answer 12

origin: 2 heads
- humeral head: medial epicondyle
- ulnar head: medial + posterior surface of olecranon

Question 13

flexor carpi ulnaris; innervation + actions

Answer 13

innervation: ulnar nerve

actions: flexes wrist at radiocarpal joint, flexes 5th CMC joint, adducts hand

Question 14

flexor digitorum superficialis; origin + insertion

Answer 14

origin:
- medial epicondyle of humerus
- coronoid process of ulna
- anterior surface of radial shaft (distal to tuberosity)

insertion:
- middle phalanges 2-5 (palmar surface, either side of base

Question 15

flexor digitorum superficialis; innervation + actions

Answer 15

innervation: median nerve

actions: flexes proximal and middle phalanges of digits 2-5 [i.e. at MCP/PIP joints]

'’superficialis divides in two, to allow profundus to pass through’’

Question 16

relations of superficial flexors (5)

Answer 16

there are 5 superficial flexors, like 5 digits of your hand all have an attachment to medial epicondyle of the humerus

4 fingers show distribution that spells ‘‘PFPF’’ [Pass, Fail, pass, fail]
> Pronator teres, Flexor carpi radialis, Palmaris longus, Flexor carpi ulnaris

Question 17

pronator quadratus; origin + insertion

Answer 17

origin:
-distal 1/4 of anterior ulna

insertion:
-distal 1/4 of anterior radius

Question 18

pronator quadratus; innervation + actions

Answer 18

innervation: anterior interosseous branch of median nerve

actions: pronates forearm at radioulnar joint, stabilises radioulnar joint

Question 19

flexor pollicis longus; origin + insertion

Answer 19

origin:
- mid-anterior surface of radius and adjacent interosseous membrane
- sometimes it may also have a narrow slip that attaches to the coronoid process or medial epicondyle

insertion:
- palmar surface of distal phalanx of thumb

Question 20

flexor pollicis longus; innervation + actions

Answer 20

innervation: anterior interosseous branch of median nerve

actions: flexes thumb

Question 21

flexor digitorum profundus; origin + insertion

Answer 21

lies deep to flexor digitorum superficialis ..
… profundus means deep in latin

origin:
- proximal 2/3 of anterior ulnar shaft and adjacent interosseous membrane

insertion: palmar surface of distal phalanges 2-5

Question 22

flexor digitorum profundus; innervation + actions

Answer 22

innervation:
- medial 1/2: ulnar nerve
- lateral 1/2: anterior interosseous branch of median nerve

actions: flexes distal phalanges of digits 2-5

Question 23

flexor retinaculum - attachments

Answer 23

• lateral/radial: scaphoid and trapezium
• medial/ulnar: pisiform and hamate
• prevents bowstringing of tendons in forearm

Question 24

what muscle act on elbow flexion

Answer 24

• brachialis
• biceps brachii
• brachioradialis
• pronator teres

Question 25

what muscle act on wrist flexion

Answer 25

- flexor carpi ulnaris - flexor carpi radialis - palmaris longus - flexor digitorum superficialis - flexor digitorum profundus

Question 26

what muscle act on wrist - radial deviation [abduction] & ulnar devaition [adduction]

Answer 26

radial deviation [abduction] - flexor carpi radialis ulnar deviation [adduction] - flexor carpi ulnaris

Question 27

arterial supply to forearm

Answer 27

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

Question 28

interosseous arteries

Answer 28

Ulnar artery: branch towards interosseous membrane >Common interosseous artery Common interosseous artery divides into: >Anterior Branch >Posterior Branch *Posterior interosseous artery pierces interosseous membrane to enter posterior forearm compartment. *Posterior interosseous artery: recurrent branch that anastomoses with the middle collateral branch of the produnda brachii. Together these supply the middle posterior part of the elbow. *Anterior interosseous branch descends on the anterior surface of the interosseous membrane. *Distally, it pierces through interosseous membrane and assists the posterior interosseous branch to supply the distal posterior forearm compartment.Both anterior and posterior branches supply the proximal radioulnar joint and course distally, supplying nearby nerves, muscles, etc

Question 29

radial artery

Answer 29

Proximally lies on muscle, deep to brachioradialis. If brachioradialis is pulled aside the full radial artery can be seen Radial recurrent artery branches from the proximal radial artery and anastomoses with radial collateral branch of brachial artery to supply lateral elbow As it approaches the distal forearm, it now lies directly on radius and is very superficial. It can easily be palpated! Pulse Radial artery and its branches supply muscles, nerves etc...of the lateral forearm

Question 30

ulnar artery

Answer 30

Courses distally from its origin, along the ulnar (medial) side of the forearm. It runs deep to flexor carpi ulnaris but superficial to flexor digitorum profundus (i.e., between them) Ulnar artery and its branches supply muscles, nerves etc. of the medial part of the forearm *mainly those in anterior flexor compartment

Question 31

termination of radial / ulnar arteries

Answer 31

form palmar arches of the hand - superficial - deep

Question 32

deep veins

Answer 32

radial veins ulnar veins posterior interosseous vein anterior interosseous vein brachial vein axillary veins middle perforating veins

Question 33

superficial veins

Answer 33

cephalic vein (lateral) basilic vein (medial) median antebrachial (variable) median cubital vein basilic vein

Question 34

forearm nerves

Answer 34

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

Question 35

median nerve

Answer 35

*Enters forearm at cubital fossa, gives off anterior interosseous branch *Median Nerve *Passes over ulnar artery and continues distally between flexor digitorum superficialis and profundus *Innervates most of the muscles in anterior compartment *Passes distally between flexor digitorum superficialis and profundus and exits forearm through carpal tunnel at wrist *Anterior interosseous nerve *Runs distally along the anterior part of interosseous membrane and innervates the anterior compartment muscles

Question 36

ulnar nerve

Answer 36

*Descends posterior to medial epicondyle *Enters forearm between two heads of flexor carpi ulnaris *Descends distally between flexor digitorum profundus and flexor carpi ulnaris and medial to ulnar artery *Ulnar nerve enters the hand superficial to flexor retinaculum and lateral to carpi ulnaris tendon

Question 37

sensation of forearm

Answer 37

*Don’t forget, our forearm is separated into different sensory areas as shown: *Medial cutaneous nerve of the forearm *Direct from medial cord of brachial plexus *Lateral Cutaneous nerve of the forearm *Continuation of musculocutaneous nerve distal to motor branches in arm *Posterior Cutaneous nerve of the forearm *Branch of radial nerve *If these nerves were injured, one would experience paraesthesia in their area of coverage *If these nerves were severed, the area of coverage would be fully denervated and be numb