L8: Musculo-neuro-vascular systems of the arm and anterior compartment of the forearm Flashcards
compartments of forearm
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
compartment syndrome
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
anterior compartment (8) of forearm;
> superficial muscles (5)
pronator teres
flexor carpi radialis
palmaris longus
flexor carpi ulnaris
flexor digitorum superficialis
anterior compartment (8) of forearm
> deep muscles (3)
flexor pollicis longus
flexor digitorum profundus
pronator quadratus
general rule
anterior forearm supplied by
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
pronator teres; origin + insertion
origin:
-medial epicondyle of humerus
-coronoid process of ulna
insertion:
- anterior surface of radial mid-shaft
pronator teres; innervation + actions
innervation: median nerve
actions: pronates forearm at radioulnar joint, weak flexor of elbow joint
Flexor carpi radialis; origin + insertion
origin:
- medial epicondyle of humerus
insertion:
- palmar surface of base of metacarpals 2 and 3
Flexor carpi radialis; innervation + actions
innervation: median nerve
actions: flexes wrist (radiocarpal) joint, weak radial deviation of wrist
palmaris longus; origin + insertion
origin:
- median epicondyle of humerus
insertion:
- flexor retinaculum
- palmar aponeurosis
palmaris longus; innervation + actions
innervation: median nerve
actions: flexes hand at wrist (radiocarpal) joint, tightens palmar aponeurosis when gripping
flexor carpi ulnaris; origin + insertion
origin: 2 heads
- humeral head: medial epicondyle
- ulnar head: medial + posterior surface of olecranon
flexor carpi ulnaris; innervation + actions
innervation: ulnar nerve
actions: flexes wrist at radiocarpal joint, flexes 5th CMC joint, adducts hand
flexor digitorum superficialis; origin + insertion
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
flexor digitorum superficialis; innervation + actions
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’’
relations of superficial flexors (5)
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
pronator quadratus; origin + insertion
origin:
-distal 1/4 of anterior ulna
insertion:
-distal 1/4 of anterior radius
pronator quadratus; innervation + actions
innervation: anterior interosseous branch of median nerve
actions: pronates forearm at radioulnar joint, stabilises radioulnar joint
flexor pollicis longus; origin + insertion
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
flexor pollicis longus; innervation + actions
innervation: anterior interosseous branch of median nerve
actions: flexes thumb
flexor digitorum profundus; origin + insertion
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
flexor digitorum profundus; innervation + actions
innervation:
- medial 1/2: ulnar nerve
- lateral 1/2: anterior interosseous branch of median nerve
actions: flexes distal phalanges of digits 2-5
flexor retinaculum - attachments
- lateral/radial: scaphoid and trapezium
- medial/ulnar: pisiform and hamate
- prevents bowstringing of tendons in forearm
what muscle act on elbow flexion
- brachialis
- biceps brachii
- brachioradialis
- pronator teres
what muscle act on wrist flexion
- flexor carpi ulnaris
- flexor carpi radialis
- palmaris longus
- flexor digitorum superficialis
- flexor digitorum profundus
what muscle act on wrist - radial deviation [abduction] & ulnar devaition [adduction]
radial deviation [abduction]
- flexor carpi radialis
ulnar deviation [adduction]
- flexor carpi ulnaris
arterial supply to forearm
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
interosseous arteries
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
radial artery
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
ulnar artery
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
termination of radial / ulnar arteries
form palmar arches of the hand
- superficial
- deep
deep veins
radial veins
ulnar veins
posterior interosseous vein
anterior interosseous vein
brachial vein
axillary veins
middle perforating veins
superficial veins
cephalic vein (lateral)
basilic vein (medial)
median antebrachial (variable)
median cubital vein
basilic vein
forearm nerves
- median nerve and anterior interosseous branch
- ulnar nerve
- radial nerve and posterior interosseous branch
median nerve
*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
ulnar nerve
*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
sensation of forearm
*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
