So I'm going to just quickly run you through some of the functions of the large terminal
nerves. So we'll start off with the musculocutaneous nerve which comes off the lateral cord.
This nerve is responsible for innervating the three flexor muscles of the anterior compartment
of the arm. So we've got the biceps brachii muscle, the brachialis muscle and the coracobrachialis
muscle.
So the ulnar nerve is responsible for innervating all intrinsic muscles of the hand except for
the thenar muscles and the lateral two lumbricals, which are innervated by the median nerve.
So as the ulnar nerve passes through the forearm into the hand, it innervates two muscles in
the forearm. It innervates the flexor carpi ulnaris muscle and the medial half of the
flexor digitorum profundus muscle. So I've just isolated those muscles on this model.
You can see the flexor carpi ulnaris muscle and you can see the flexor digitorum profundus
muscle.
In the hand, the ulnar nerve is responsible for innervating all the intrinsic muscles
except for the thenar muscles. So we've got the abductor pollicis brevis, the flexor pollicis
brevis and the opponens pollicis. And also, you've got the lateral two lumbricals here.
So you've got the thenar group of muscles here and you've got the lateral two lumbricals
over here and these are innervated by the median nerve, but all the other intrinsic
muscles are innervated by the ulnar nerve.
So in terms of sensory innervation, the ulnar nerve provides innervation to the medial one
and a half finger. So you've got the little finger and half of the ring finger. And you've
also got innervation provided over the medial aspect of the hand and the wrist, on the palmar
surface.
And on the dorsal surface of the hand, you can see the area of innervation provided by
the ulnar nerve. So you've got the medial part of the dorsal surface of the wrist and
hand innervated by the ulnar nerve.
So the median nerve is formed by the union of these roots that come from the lateral
and medial cords. So you've got the lateral root from the lateral cord and the medial
root from the medial cord. They unite and the median nerve is formed anterior to the
last part of the axillary nerve.
So this diagram illustrates it quite nicely. So you've got the lateral cord and you've
got the medial cord. You've got the lateral and medial roots of the median nerve uniting
in front of the axillary artery to form the median nerve.
So the median nerve innervates all the other muscles of the anterior compartment which
the ulnar nerve doesn't innervate. So it innervates all the muscles except the flexor carpi ulnaris
and the medial half of the flexor digitorum digitorum profundus muscle.
And in the hand, you know which muscles are innervated because it's the ones that are
not innervated by the ulnar nerve. So you've got the thenar muscles and the lateral two
lumbricals, which are innervated by the median nerve.
In terms of sensory innervation, you can see the distribution of innervation in pink here.
So the median nerve innervates the lateral 3 ½ digits. So you've got the thumb, index,
middle and half of the ring. And then you've got the lateral surface of the wrist and the
hand. So this distribution of sensory innervation provided by the median nerve.
So coming to the terminal nerves of the posterior cords, you've got the axillary nerve and the
radial nerve. So the axillary nerve provides innervation to three muscles. So you've got
the deltoid muscle here. You've got the teres minor muscle. And also, it innervates the
long head of the triceps brachii muscle.
And in terms of sensory innervation, you've got a branch which comes off the axillary
nerve called the superior lateral cutaneous nerve of the arm. This nerve innervates the
area of skin and the deltoid region. So you can see this area of innervation in blue here.
And on the posterior surface, it has this distribution of sensory innervation.
Just while we're on this image here, I forgot to mention earlier that the musculocutaneous
nerve actually terminates as the lateral cutaneous nerve of the forearm. You can see this area
of sensory innervation laterally on the forearm as the name suggests. So this is an anterior
view. Posteriorly, you can see this area of innervation. So that's the lateral cutaneous
nerve of the forearm.
The final nerve is the radial nerve. So this is the largest terminal branch of the posterior
cord. This nerve innervates all the muscles in the posterior compartment of the arm and
the forearm.
It also provides innervation to the skin on the posterior surface of the arm and forearm.
You can see this distribution in pink here. So branches of the radial nerve innervate
the skin on the back of the arm and forearm. And also on the dorsal surface of the hand,
you've got this area of innervation.