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Nerves of the upper limb (anatomy)

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This content provides a visual and anatomical overview of the major nerves of the upper limb, focusing on the "big four" (musculocutaneous, median, ulnar, and radial nerves) and their pathways from the shoulder to the hand, along with a discussion of cutaneous innervation.

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hello again you guys are feeling a bit

busy today today we're going to look at

the nerves of the upper limb I'm not

gonna cover the brachial plexus I am

gonna cover the big four nerves has been

run down from the shoulder distally

towards the hand the aim is to have like

a visual idea of where those nerves run

by the big4 I mean musculocutaneous

median ulnar and radial whenever you

have a list of things like why is the

last one always hard to understand cough

anyway before and then I'm gonna add in

a few extras and just for fun we're

gonna talk about the cutaneous nerves -

the skin of the upper limb as well all

right I'm really going to say about the

brachial plexus is that it arises in the

neck so one week we'll have a look at

the nerves in the neck we'll have a look

at the nerves around the shoulder shall we

but the brachial plexus pops out between

the anterior and the middle scalene

muscles of the neck those muscles are

running between the cervical vertebrae

and the ribs so that the roots of the

brachial plexus pop out from there and

then they they get into the Zillah and

when they're in the axilla we see the

cords forming around the exilair artery

and then we go into the upper limb the

main purpose of the brachial plexus then

is to carry nerves from well spinal

nerves from the spinal cord acting to

the upper limb and the brachial plexus

is making those four main nerves but

it's also making a few other little

nerves so there are lots of nerves

around the shoulder region here which

I'm not going to talk about but we'll

start in here so that's what we're

seeing on this model here this model

here is the right arm it's upside down

right so

deltoid um mm-hmm

so what's in this princess is bigger

than mine oh it's bad thing it's what's

losin tit so that's what we're seeing up

here we're seeing the past the brachial

plexus and this is the angular II artery

this artery is a good landmark because

we're following these nerves into the

upper limb it starts off as the

subclavian artery when it runs by the

clavicle is it passes the first rib then

it becomes the axillary artery it goes

into the exhilarate passes

I think distal to teres major so around

there we then call it the brachial

artery so there's a bit of terminology

as well this part of the arm up here the

upper arm you might say we call the

brachial so you might find nerves which

have you know the term brachial in them

better that they're in this region and

then the rest of the arm to the wrist

this is the what we might call the

forearm also gets called the

antebrachium so like cutaneous nerves in

this region get called the you know anti

anti anti brachial nerves

so like the medial antebrachial the the

medial cutaneous antebrachial nerve

something like that which miles called

the medial continuous nerves of the

forearm I'm gonna use for arm without

arm today we came across antebrachium

and break him

that's all they all they mean right

breaking antebrachium anywho so here's

that auxilary artery and you can see it

there it's surrounded by these nerves

that are forming from the brachial

plexus now if we look so is biceps

there's the anterior surface of the

scapula there's a clavicle there and if

we turn this around so here who are the

tendons of biceps you can see in here

we've got a couple of nerves coming off

the brachial plexus and going kind of

post earring Lior laterally so we've got

the humerus running in here haven't we

now those two nerves they would you see

to live there because there are all

there's another one there are three

nerves in here which are like running

kind of kind of disappearing

and we've got the axillary nerve and the

radial nerve and we've also got the

musculocutaneous nerve now if we take

the anxiety nerve that's the first one

on the exhuming nerve then ah there we go

I'll see it here so the axillary nerve

is this branch here it's this branch

here and it's nipping in there and it's

passing passing here through this gap

and what its gonna do is it's gonna it's

gonna kill arraign the surgical neck of

the humerus by which I mean is the

humerus it's gonna it's gonna curl

around on the surgical neck of the

humerus here and it's gonna pop out

their posterior Li and that's the turn

this around so there's the head of the

humerus there's the surgical neck of the

humerus there it is there as popping out

popping out here right so what the

axillary artery is good sorry what the

exilic nerve is going to innovate is the

deltoid muscle right so this muscle here

it's also going to innovate some of the

skin around them I'll come back through

cutaneous innovation at the end so then

the auxilary nerve the reason is

wrapping around like this is to get to

innovate the the deltoid muscle out here

and also to get to teres minor so on the

scapula we've got this is the spine of

the scapula super space is up here

infraspinatus and teres minor there and

terah's major here now if you look the

nerve equality laughing Villere nerve

now the other nerve I like also I'm not

be able to see on this one okay

I've these three branches here second

one is the musculocutaneous nerve and

the third one because we can see this is

going into choice if the third one is

the radial nerve the radial nerve is

essentially doing the same thing it's

gonna run post II really around the

humerus to get to the posterior

compartment its main job here is to

innervate triceps so the extensors of

the elbow this posterior compartment of

the arm it's also gonna carry cutaneous

innervation from the

and there it is there now this wraps

around the humerus

more inferior ly but there's the radial

nerve the radial nerve it comes around

in this direction but it winds its way

around the humerus kind of Ryan the mid

shaft so this means that a fracture of

the humerus could damage one of these

nerves if the fracture is up at the

surgical neck there's a risk of damaging

the angular II nerve and if the fracture

is kind of in the mid humerus mid shaft

then there's a twisted in it then

there's a risk of damage the radial

nerve I can see a bit of a spiral a

spiral shape to that to the bone here

there is a video on the humerus where we

talked about the detail the detailed

bits of the humerus and there is a

groove a spiraling also if orthopedic

surgery is maybe repairing a bone after

a fracture the surgeon also has to watch

out the radial nerve they weren't

screwing things back again now the elbow

so this is the cubital fossa right in

the anterior part of the elbow if I take

off so we've got brachioradialis here

and what-have-you if I take that off

then we can see the radial nerve so this

means that the radial nerve this is the

lateral epicondyle of the humerus

so this lateral epicondyle here right so

on you at your elbow you've got your

medial epicondyle here this bony bit in

your lateral epicondyle there that bony

bit this means that the radius then is

actually coming around anteriorly so

although it's innovating the posterior

compartment of the arm the radial nerve

comes around anteriorly at the elbow

anterior to that that epicondyle and

that's what we see here and then it

splits into superficial and deep

branches now we can see the superficial

branch here now that we've taken this

month this muscle layer off now the

superficial branch is just gonna carry

cutaneous innervation as it descends

down here we can see it popping up again

if I put this back on

you get an idea of yeah come here but

the the radial nerve disappears it

splits into superficial and deep

branches a superficial branch look it's

popping up here between the tendons and

then it's quite famously passing to the

the posterior hand here there's the

thumb these are the fingers so this is

the radion that the superficial branch

of the radial nerve here which means

that it's gonna carry sensory

innervation from from this region here

right the posterior part of the hand

around the thumb around here the what we

call this anatomical snuffbox that's the

one achoo

yeah so right now it's almost enough

boxing this part of the hand here so

that's radial nerve superficial branch

now the deep branch can we see the deep

deep branch no the deep branch goes deep

and the deep branch is going to be

responsible for innovating the muscles

of the posterior compartment of the

forearm that is the muscles that extend

your wrist right radial nerve so that's

the branch of the radial nerve is just

it's just passing back around again to

the posterior compartment of the forearm

it was innovating all of these guys all

right so that's the radial nerve right

now if I go back up to the top I said

there are 1 2 3 branches there the

second one the musculocutaneous nerve I

think about the name of that

musculocutaneous glut cutaneous means

it's gonna be motors and muscular stuff

and sensory from cue subcutaneous stuff

some skin stuff right the

musculocutaneous nerve is going to run

to the anterior compartment of the of

the upper arm this model doesn't come apart

apart

we man I think does what can we see here

these pectoralis minor he's biceps it's

coracobrachialis yeah because we're seen

Musto cutaneous diving up into here to

get underneath biceps so if we take

biceps off there we go that here's a the

proximal humerus here and there's the

musculocutaneous nerve so that's the job

of the musculocutaneous nervous to

innervate the flexors of the upper arm

and that's it so it's carrying to the

anterior compartment of the upper arm is

going away these three muscles here so

basically is gonna innervate the muscles

that flex the elbow biceps brachii

coracobrachialis and brachialis and

that's the end of it if it's muscular

job it does continue of course this is a

left arm right left arm here and we can

see it continuing when it pops out again

it disappears on here but not too

surprisingly because it's a cutaneous MA

a cutaneous nerve which means it because

the skin has been taken away

we've lost the cutaneous nerves as well

just like we've lost those those

superficial veins that we can we can see

in the skin of our arms right the

musculocutaneous nerve is going to

continue is the lateral cutaneous nerve

of the forearm which means it's gonna

it's gonna carry sensory innervation

from the so it's going to carry sensory

innervation from the skin and the

lateral part of the forearm here now the

radial nerve is going to I've got I've

got a fake nerve here now the radial

nerve okay if we stick with the left arm

so we saw the range of nerve is coming

around around here right before it comes

around the elbow it sends off a before

the radial nerve splits into the

superficial and deep branches

it gives off a a posterior cutaneous

nerve of the forearm like this and that

splits off a you know proximal to the

elbow so above the elbow and then gives

off a branch so the radial nerve and

this posterior continues near the

forearm is actually carrying the sensory

innervation from the posterior part of

the forearm and then the muscle of

cutaneous nerve is carrying sensory

innervation from the the lateral part of

the forearm through the lateral

cutaneous nerve the fourth all right so

we've got a medial cutaneous nerve to

discover later so that means that we

have taken care of the muscles of the

arm with the musculocutaneous nerve and

the radial nerve now we've still got the

median nerve and the ulnar nerve to deal

with and that's what we see here now

look this is biceps brachii remember

this is the right arm arms everywhere

this is this is the right arm

here's biceps brachii there's triceps

brachii si brachii brigham and the

artery the brachial artery is running in

this groove in between the two and

you've got we go in there

coracobrachialis whatever so you've got

the brachial artery running in this

groove which means it's very superficial

and we talked about this when we talked

about the arteries of the upper limb you

can you can get in here and feel the

pulse now where you feel the pulse where

you feel that artery you can also feel

you some other firm round structures

that are very nice to poke two of those

structures are the median nerve and the

ulnar nerve and you know where the ulnar

nerve goes because of your funny bone

right but the median nerve is following

the brachial artery this is the cubital

fossa here of the anterior elbow and it

the brachial artery is running around

anteriorly into the cubital fossa and

then it disappears behind these muscles

so here's pronator terrors and we start

to get into the muscles of the forearm

if we take those away we can see a

little bit more whoo right so

we get into the cubital fossa that

anterior part of the elbow you can see

the brachial artery comes around and

splits into ulnar and radial arteries

the median nerve comes around with it

before the median nerve before the

brachial artery splits the median nerve

then disappears beneath these muscles so

that goes away from it a little bit the

median nerve then is going to run into

the anterior compartment of the forearm

I've got to take off another muscle

layer to see it so we're with the same

thing quite deep here but there's the

median nerve there there's the ulnar

artery there's the radial artery so

we're very very deep the median nerve is

going to innervate all of the muscles of

the anterior compartment of the forearm

except for flexor carpi ulnaris which is

going to be innovated by V on the nerve

copy Oman and also we've got flexor

digitorum profundus that's the deep

muscle that flexes the fingers that's

going to be partially innervated by the

median nerve and partially innovated by

the ulnar nerve but the median nerve

otherwise is innovating all of the other

muscles of the anterior can pump to the

forum and those muscles are involved in

flexion of the wrist and and flexion of

the fingers right now the median nerve

continues and look it's still deep it's

still disappeared it's going to go deep

to the flexor retinaculum and at the

wrist which is which is there right

which means that the median nerve is

running through the carpal tunnel now if

we look at the carpal tunnel we've got

another video on that there's the bones

of the wrist and making a groove here

right and making a space and blood

vessels and the median nerve run through

it's going to innervate the muscles of

the thenar eminence these are the

muscles of the base of the thumb it's

also can we innovate the lumber cause I

think got video on that too and so the

median nerve then is it's sensitive to

being come

rest within the carpal tunnel it's a

carpal tunnel syndrome information of

the synovial bits and bobs in there

compression for carpal tunnel is likely

to affect the median nerve and the

median nerve then it's going to carry

sensory innervation from the skin on on

this side of the hand like the thumb

solid of the hand and over the top of

the fingers remember the radial nerve is

doing the other side of the hand

all right median nerve i've got i've got

a whole elearning thingy on this

somewhere which i made with some digital

meat very very talented digital media

students who wanna go so that's the

median nerve okay there's one left now

the big four let's put this back

together so the final nerve of the big

four is the ulnar nerve and the ulnar

nerve loss were up here again it's

running with the brachial artery it's

running with his collateral branch to

the elbow but the ulnar nerve the

important thing about the ulnar nerve is

that it's also in this in this gap here

but it runs posterior so the the medial

remember this is the right hand post

here it's the medial epicondyle of the

of the humerus so that means it's

running well there's the medial

epicondyle so it's running posterior to

the medial epicondyle around there and

you know this because when you bang your

funny bone here when you bang your

medial epicondyle it hurts and you get a

tingling shooting down your forearm on

this side to your little finger which

also then tells you what the ulnar nerve

does I think very nice to poke you you

can camp out Bait it we were the only

nerve then runs around the medial

epicondyle and it runs down here so we

can see that on the big arm model

remember this is a right hand still so

we lose the ulnar nerve here as it goes

deep we can't see it because it's

covered by these muscles it's safe again

down here it's vulnerable up here in the

arm in the forearm it's it's pretty deep

we can see it appear

came down here towards the wrists if I

if we dissect deep we'd go deep and take

all these muscle layers off there we go

there's the ulnar nerve running down

there so it's very much running on me

you know the the on the side of the ulna

and as I said it's going to innervate

flexor carpi ulnaris it's going to

contribute innovating flexor digitorum profundus

profundus

the deep flexor of the fingers in here

but look it's going into the hand you

can see it's going over the top of so

it's superficial to the flexor

retinaculum so the ulnar nerve is not

affected by carpal tunnel syndrome and

then it's um it's giving off a whole

bunch of branches into the hand and the

posterior hand here as well so it's

gonna the ulnar nerve is innovating most

of the intrinsic muscles of the hand the

median nerve is innovating these guys

over here in some of the lumbricals the

ulnar nerve is doing the rest and also

think about the skin that we haven't

innovated yet so the the divider is

typically halfway down the fourth finger

right so one to do so halfway down this

finger this side is innervated by the

median nerve this side is innovated by

the ulnar nerve and also post eerily

right so on the median radial nerve so

if you want to test if a cutaneous part

of these nerves are working you can just

you know test for sensation here radial

test for sensation here medial test for

sensation here on the nerve who's that

so those are big four it's difficult

with these models that you can't rotate

and stuff I mean I often use

computer-generated images for teaching

this along with these models because

it's difficult to see the roots but but

visualize how the musculocutaneous nerve

runs into the anterior compartment d2

biceps brachii how the radial nerve gets

around into the posterior compartment

and then comes around to the cubital

fossa then splits into deep and

superficial branches which carry on down

superficial is then going you know

that that region there and the deep is

going to innovate all of the muscles of

the posterior compartments just

visualize the the ulna and the median

nerves the median nerve staying in the

middle so it's coming around anterior to

the medial epicondyle it's getting to

the cubital fossa innovate all of the

muscles of the of the anterior

compartment all except one and a half

and then gets down into the the thenar

eminence the thumb and the hand biko

going through the carpal tunnel and then

visualize the ulnar nerve running around

posterior to the medial epicondyle of

the humerus and innovating flexor carpi

ulnaris in continuing down to innervate

most of the intrinsic muscles of the

hand flow right get the the shapes get

the flow that's the important thing you

read these descriptions in textbook

sounds very complicated visualize the

shapes it's not so bad so those are the

big four and while we were going through

there we've talked about a bunch of

cutaneous nerves but let's add a few

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YouTube Transcript:Nerves of the upper limb (anatomy)