hello everybody welcome back i hope you're all doing well today we're going to have a look at the anatomy of the internal carotid artery we're going to follow its course all the way through the neck through the skull base and into the cerebrum and then we're going to have a closer look at the artery itself define the various segments of the artery and look at the branches that come off each of those segments so i'm going to start by having a look at a ct scan here where we're just going to get a broad overview of how the carotid runs all the way up into the circle of willis and then we're going to go on to an mr angiogram where we can look at the anatomy of the crotid in much more detail so here we have an axial contrasted arterial phase ct i want to scroll right down in the chest we're going to start at the heart and work our way all the way up so follow the trachea down it should bifurcate here at the carina here we know we can see our pulmonary trunk here our ascending aorta and our descending aorta and as we work our way up we'll see the arch of the aorta starting to form now we know that there are three branches that come off the aorta here we can see one two three so let's name them it's our brachiocephalic trunk our left common carotid now there's no such thing as a carotid artery it's either common carotid or internal or external carotid artery and then our left subclavian so let's just check that this is our left subclavian we should see it going out towards the periphery that's right as we come down then we can see our left subclavian and we know that this is our left common carotid artery so let's follow the left common carotid all the way up we're just going to track it up the neck i'm scrolling superiorly here you can follow my mouse i'm on the common carotid artery here we go through the neck and it should bifurcate we can see a bifurcation there it splits into two now posteriorly and medially is normally your internal carotid artery and this is our external carotid artery so we're going to follow the internal carotid moving our way up the neck it can have a bit of a torturous course you can see it going laterally here coming in medially again and up towards the skull base we can see at the level of the skull base here it then goes into the petrol section of the temporal bone now if you haven't seen the anatomy lecture on our skull based foramina that's a great one to go and have a look at because our carotid goes through a couple of those channels we can see it then come anterior immediately through the carotid canal up to the level of the foramen less it comes upwards before diving forward through our cavernous sinus here we can see our anterior clinoid processes and then the cross it wraps back round up towards the circle of willis where it gives us our middle cerebral or anterior cerebral artery and we can't see it here but our posterior communicating artery so let's go all the way back down let's follow the right hand side one it's slightly different obviously because of this brachiocephalic trunk so the brachiocephalic trunk should split into two let's watch it there there we split into two this will be our right common carotid artery this will be our right subclavian artery let's just make sure that this is a subclavian it's going out towards the periphery there perfect so let's follow our right common carotid artery we work our way up the neck again keep following it and there we go we see a bifurcation a split external carotid artery internal carotid artery we follow that internal carotid artery upwards keep going up keep going up and we should see it now we can see our two vertebral arteries here we can see how common karate coming towards the skull base you see it jumps across left there a little bit but that's fine up into the carotid canal anterior immediately past the foramen less serum we come further upwards and then we dive forward past or through the cavernous sinus up past the anterior clinoids coming backwards splitting into our middle and anterior cerebral arteries and we can just see our posterior communicating artery there now we can do a 3d reconstruction of this so here we can see this is now the right hand side of the patients our brachiocephalic trunk our right common carotid coming off it and our internal carotid making its way up to the level of the carotid canal we come anterior immediately past the foramen lacerum up towards the level of the cavernous sinus now the arteries coming straight out towards us here so i'm going to just keep my mouse at this level so we maintain our level and just rotate it around so we're at this level we can see we've come through the petrous bone passed the foramen last serum up towards the cavernous sinus wrap around past the anterior clinoids and come over the top of the cavity sinus there and i want you to remember that loop there because where we are here is next to the cellulosica coming over and we in that middle bit got the pituitary gland there and that's going to really help us in naming some of the branches later and then we come up and split into our anterior and middle cerebral arteries so let's have a look at it in a little bit more detail i'm going to switch over now to the mra the mr angiogram and let's look at it here we're at the level of the circle of willis here at the vasculature his hair is bright our arteries are bright and let's scroll down again to the neck let's see how far down the scan goes so here we are we can see our vertebral arteries here coming up next to our spinal cord we can see our internal carotid arteries here we've already bifurcated and let's now name the segments of the internal carotid artery so there's seven segments i'm going to list those segments here next to the video as we come across them and if we have any branches coming off i'm going to tell you what those branches are so the segment in the neck after the bifurcation all the way up to the opening of the karate canal that's what's known as the cervical section or c1 so let's follow that this is all c1 follow follow follow and here we can see it coming into the karate canal this is the opening of the carotid canal in the petrol section of the temporal bone and this is the beginning of c2 or petrus segment of the carotid artery so the petro segment runs through the carotid canal comes anteriorly until we reach our foramen less serum this section that now comes upwards that takes a little right angle out is the lacerum segment and that is segment c3 so we follow that segment we're going superiorly now we can see our basilar artery here and these are our this is our cereal the serum segment c3 of the carotid artery working our way up and we now expect it to go forward into our cavinus sinus which you can see it here going forward this is c4 the cavernous segment of the internal carotid you can see then it comes out anteriorly and goes upwards and posterior so it loops around like we saw in that ct reconstruction and where that loop happens is the anterior clinoid process and this segment is segment c5 it's called the clinoid segment segment c5 of our internal carotid artery so there we can see it coming in coming around this is c5 then we're going to head back posteriorly this segment that starts to bend back posteriorly is called our ophthalmic division c6 ophthalmic division before heading upwards towards the circle of willis and giving off our posterior communicating artery and bifurcating into our anterior and middle cerebral arteries that last segment c7 is what's known as the communicating segment of the internal carotid artery now some of these segments have branches coming off them and i'm going to head back down into the neck it's nice to remember because the even segments c2 c4 and c6 they each have two branches coming off and then c7 has a couple of its own branches so let's go to segment c2 the petrus section here we are lateral to this is the tympanic membrane so that's the first way to remember our first branch which is which is a critical tympanic branch and then if you've watched the foramen video uh the skull base for raymond we see that there's a artery coming off we can't actually see it on the scan which is called the vidian artery coming off through the vividian canal into the pterygopalatine fossa not not everyone has this artery but that is our second branch of c2 the vidian artery moving our way up now we're in the cereal section c3 there's no branches of that and we're going to head forward now into the cavernous sinus this is c4 and we know that we have two branches coming off c4 now if you picture where we are our pituitary gland the inferior segment here of the pituitary gland is medial to our cavity sinus here and then we know that we loop around superiorly later so this first branch that comes off here is called the inferior hypophyseal artery hypothesis our pituitary it's our inferior hypophyseal artery and that supplies the neural hypothesis the posterior segment of our pituitary gland another branch that comes off here and goes into the cranial anterior cranial fossa is our meningeal artery that supplies blood to the anterior meninges in the anterior cranial fossa then again we loop our clinoid segment c5 there's no branches of the clinoid and we come around into our ophthalmic segment now the ophthalmic segment c6 that's also got two branches and this is one branch that we should always see it's at the biggest branch that we have of the ica and that is the ophthalmic artery so let's see if we can see it here we can see on the patient's left hand side here we can see the ophthalmic artery coming off we can follow that ophthalmic artery through the optic canal heading into the orbit and the same on the other side we can follow you can see the ophthalmic artery coming off the right ear heading through the optic canals into the right orbit there the other artery that comes off c6 i said there were two we're now superior to the pituitary gland and that is the superior hypophyseal artery so our inferior hypophyseal artery is coming off our cavernous segment and our superior hypothesial artery is coming off our ophthalmic segment and that is going to be supplying the anterior portion of our pituitary gland so we can see now that we followed this curve around we now in the ophthalmic segment segment c6 we follow it around more i'm looking on the right hand side here we can see that this branch is coming off now the communicating segment c7 we're giving our posterior communicating archery coming off another branch is given off here and i'm listening them on the side you can always screenshot at the end to get all the branches uh in one place the anterior choroidal artery comes off here now that has a really wild course throughout the brain but it it goes down to the lateral geniculates of the thalamus and eventually heads all the way to the lateral ventricles and supplies the choroid plexus in the lateral ventricles hence it's named the anterior choroidal artery and then we come up into the circle of willis and we can see this bifurcation we get the anterior cerebral coming off we can actually see our anterior communicating artery linking both our anterior cerebrals and we get our middle cerebral artery coming off down the side here okay so hopefully you can understand where those segments are and a lot of people will learn this by learning a mnemonic and trying to remember the branches and there's two different mnemonics one for the ica and one for the branches and i find that a really inefficient way to learn the better way for me to learn anyway is to picture it in my mind see where the carotid is actually running you can start to think i'm going past the tympanic membrane supply here i'm going past a hypothesis i'm going to apply it there i'm going past the ophthalmic i'm supplying there and it's much better in the long term to remember it that way to actually understand why these things are called these things instead of trying to learn a mnemonic and then getting confused with all the mnemonics you have and if you like doing this if you like going through scans like this and really trying to apply your anatomical knowledge to name structures then consider subscribing to this channel this is the way that i describe it i'm looking at the actual images we can see these vessels in context with all the other anatomy around it instead of looking at a diagram in a textbook where everything's been stripped away and we only have our artery it's much more difficult then to try and see where these segments fall in now before we go there's one more way we can assess the internal carotid artery all the arteries in the in the brain and this is often done when we have suspected subarachnoid hemorrhage or an aneurysm in the brain and that's what's known as digital subtraction and geography or a dsa i'm going to show you what it looks like these are beautiful images i'm going to go straight to where we taking our image what i want to do is start at our initial image show you how to read these quickly we can see almost this indentation it almost looks like embossed paper you can see the skull coming around here our anterior cranial fossa or our roof of our orbits here cela turcica here as well as our temporal bone coming here so we kind of know where we are anterior here these are facial bones and this is the occipital bone back here so let's now be giving contrast we can see this first segment coming in is the last portion of our uh cervical segment c1 then we're going through the petrous bone this is c2 coming up past the foramen lacerum into the serum section segment three c3 diving forward into the cavernous sinus this is our cavernous c4 segment we can see that this if i go back this is our cellulosica it's got our pituitary sitting in there so we're coming right past that coming up past the anterior clinic c5 our clinic backwards giving off our ophthalmic arteries sea sick ophthalmic and then rising up into the circular bullets here our communicating segment giving our anterior and middle cerebral arteries coming off so it's a fairly complicated artery it goes a lot of places it sends off a lot of branches but these are all critically important clinically especially when you are assessing for atherosclerosis in the ica or any signs of acute thrombus or stroke and again you can follow the caliber of these arteries and actually see if you can see any aneurysms forming so i hope that helped again if you like learning like this please consider subscribing to the channel let me know what other anatomical structures you want me to discuss next and until next time goodbye everybody