hello everybody and welcome to this brand new Anatomy module I'm calling this module above the shoulders Anatomy we're combining head and neck anatomy and neuroanatomy into a single module I'm going to start today by looking at the neurocranium the bones that hous and protect the cerebrum and the cerebellum now we're going to be covering many different bones today and I want to show you those bones both with a 3D model and with a CT scan we'll start off by looking at the frontal bone and the frontal bone can be thought of as having two separate parts a vertical part and a horizontal part and let's start by looking at the vertical part we'll see on our axial bone windowed CT scan here we can scroll right to the very top of our stack we can see anteriorly the frontal bone at the front is separated from the parietal Bones by a suture that's known as the coronal suture coronal meaning crown or Garland that's where we get the coronal plain name from and the parietal bones are themselves separated by the sagittal suture now the sagittal suture will intersect the coronal suture at a point known as the bregma the bregma represents where the anterior fontel used to be and as we scroll down inferiorly we can see the coronal sutures Fanning out laterally anterior to that coronal suture is the vertical portion of our frontal bone now occasionally you may see an additional suture running down the midline here known as a persistent metopic suture when the frontal bone develops it develops from two separate oifc centers and ossifies by intramembranous ossification that fuses at the midline and sometimes we can have a persistent suture here known as a mopic suture now as we scroll down inferiorly you can see on our sagittal scan here is the vertical portion of our frontal bone we scroll down inferiorly and we will see on the internal surface a very shallow sulcus forming that's what's known as the sagittal sulcus it represents the starting point for that Superior sagittal sinus that drains Venus blood po posteriorly to the Confluence of the sinuses as we scroll down further inferiorly we can see that sagittal sulcus becomes a Crest here that's what's known as The frontal Crest now the frontal Crest is an attachment point for that double fold of jamata that separates the two cerebral hemispheres known as the folk cerebri it attaches to this frontal Crest anterior to the frontal Crest we can now see the frontal sinuses now the frontal sinuses are almost always a symmetrical and we can get these septations in the frontal sinuses they form part of the four paranasal sinuses which we're going to look at in the future talk now I've said they can be asymmetrical they can also be underdeveloped that's a hypoplastic frontal sinus or they can be absent an aplastic frontal sinus you can see they lie in this thicker portion of the frontal bone when you compare it to the other bones of the neurocranium here that thicker portion is what's known as The superer Arches you can see on our 3D model The superciliary Arches running where our eyebrows are and meeting at the midline at a point known as the glabella if we go into our sagittal scan here and scroll over to the midline this point anterior here is what's known as the gabella now you may have heard of the gabella tap sign where you tap a patient repeatedly on their gabella and the first couple of times they will blink that's a primitive reflex but they should be able to suppress that reflex and stop blinking now there's certain diseases where you can't suppress that reflex a disease such as Parkinson's and they will continue to Blink on each point that's tapping the gabella here and these structures are all part of the vertical portion of the frontal bone we can see that the frontal bone intersects with these small bones here known as the nasal Bones on the 3D model you can see the fronto nasal suture and as we head out laterally that suture becomes the frontal maxillary frontal lacrimal and frontal ethmoidal sutures we can see those sutures on the coronal scan here as we head out anteriorly sometimes quite difficult to see but we can see the frontal bone here coming down to the frontal nasal suture and this midline point here is what's known as the Nason and as we head out laterally we can see the frontal maxillary suture frontal lacal suture and we head out posteriorly to the frontal ethmoidal suture if we scroll out laterally we can see the horizontal portion of the frontal bone heading out here this is the super orbital plate which makes up the majority of the anterior cranial fosser if we look at our 3D model below the super superill arches we can see the super orbital margin now the super orbital margin is predominantly smooth but you may get a small notch or a small forment in the super orbital margin often there's two a lateral and a medial one the most lateral notch or forment is what's known as a super orbital framan or super orbital Notch and that has the Super orbital nerve running through it it's easy to remember medial to that you can get a notch known as a superat trar notch which has a superat trar nerve running through it that's not always there now those two nerves are branches of the frontal nerve which itself is a branch of the Epic division of the trigeminal nerve and those two nerves run through those notches or through those frament now why is that important to remember well if you're scrolling through the axial scan here and as you head down to the horizontal portion of the frontal bone we can see our super orbital margin here you may see there's a defect or what looks like a defect here in the super orbital margin it's important not to call that a fracture this is our super orbital for ramen here which contains a superorbital nerve now you may not always see these depending on your slice thickness but it's important not to call that pathology now the supr trar nerve it runs above the trar muscle both of these nerves run in the extraconal space underneath the horizontal part of the frontal bone now you can see the horizontal part of the frontal bone heading posteriorly and that's going to reach the sphenoid bone which we're going to look at later and that's the speno frontal suture so we've seen the vertical part and the horizontal part it's important to remember that the frontal bone also has an anterior projection called the zygomatic process of the frontal bone and that's going to head to the zygomatic bone we're going to look at the zygomatic bone in more detail when we look at the visceral Cranium you can see on the 3D model that's the frontozygomatic suture if we look at our coronal plane here and we head out anteriorly we might be able to see the frontal zygomatic suture here again is the fronto zygomatic suture it's important to know these sutures so that you don't call them fractures later on obviously if you see what you think is a suture look at the bilateral side to see if there's a corresponding suture so we've covered the frontal bone you may have noticed that when we were looking at the horizontal plate we were off midline and that's because the frontal bone those two superorbital plates has another bone that wedges in between the superorbital plates that's what's called the ethmoid bone and it also makes up some of that anterior cranial fossil FL when I talk about the anterior cranial fosser here you can see the anterior cranial fosser middle cranial fosser and posterior cranial fosser and as we go through each of the bones I'll tell you which bones make up these fosser so let's head to the midline and see that ethmoid bone jutting up between the frontal bone you can see that the ethmoid bone here has ethmoid air sinuses below another paranasal air sinus that we're going to look at in the future so let's go to our axial scan and scan down through the ethmoid bone there's the ethmoid sinuses and we had superiorly the first thing to note is you can see this Superior projection of bone known as the Christa gy it's best seen on our coronal plane there's the crystal glidey heading up superiorly it's also an attachment point for the fog cerebri and you can see here that it can contain some marrow when we look at the Crystal on a T1 weighted MRI it might be hyper intense and you mustn't confuse that for some form of pathology it can also contain air sometimes now on either side of the crystal G we can see these two fosser here that's what's known as the old factory fosser within the old factory fosser lie the old factory bulbs of the olfactory nerve and they send down nerve fibers through the ethmoid bone into the nasal cavity those nerve fibers pass through what's known as the CRI plate we look on our axial scan here we can see that the CRI plate has these perforations actually in Latin cror means perforated that's where those nerve fibers head down into the nasal cavity now the cfor plate forms the floor of the old factory fosser and we know that the crystal gy makes up the medial wall of the olfactory fosser laterally is the vertical lateral Lamela that's what this bone is called here and as it turns out horizontally this is known as the fobia ethmoidalis it's part of the frontal bone actually so the fobia ethmoidalis becomes the lateral vertical Lamela the CRI plate and the Crysta that makes up the old factory foser now we're not going to look at the ethmoid air sinuses within this talk that's going to be for a future talk we're just looking at the superior portion of the ethmoid bone that makes up part of the neurocranium now on our axial scan we can see the ethmoid bone here the cror plate it heads out posteriorly and also intersects with the sphenoid bone we can see very slightly here the sphenoethmoidal suture so the sphenoid bone is naturally the next bone that we're going to look at it interacts with both the frontal bone and the ethmoid bone and it actually has a suture with every bone of the neurocranium now the sphenoid bone is very difficult for people to conceptualize and that's because its 3D Anatomy is complicated now I find it best to split the sphenoid bone into its four main parts and look at each part in isolation now the sphenoid bone has a body it's got lesser Wings greater wings and teroid processes now in today's talk we're not going to look at the teroid processes cuz that's part of the viscerocranium like the ethmoid bone we're going to look at the superior surfaces that make up the neurocranium let's start by looking at the body of the sphenoid bone some of the body makes up the floor of the anterior cranial fosser and then we dip down into what's known as the cello it's best looked at on our sagittal plane where we can see we're at the midline here if you see our green lines here we're at the midline and we can see that the roof of the sphenoid sinus here is what's known as the sphenoidal Yol that's part of the body of the sphenoid then we dip down into the celotto or the Turkish saddle the anterior part here of the cell Tura is what's known as The tuberculum Cellar and laterally we've got these two clinoid processes known as the middle clinoid processes we then head into our hypophysial fosa that's where the pituitary gland sits and the posterior margin of the celosa is the dorsum cellar and again laterally we've got posterior kinoid processes let's look what that looks like on our axial slice we head down inferiorly we can see our tuberculum cell here and as we head down inferiorly we can see our middle kinoid processes the hypothal fosa and the dorsum cellar with the posterior kinoid processes laterally you can almost just see here the cored arteries that's what's known as the cored sulcus and as we head down inferiorly we're heading down towards the cus of the occipital bone so that's the body of the sphenoid bone it's got the anterior portion which is the sphenoidal yolk we head down into the celotto and then we head down towards the clus now the Lesser wings of the sphenoid lie on either side of the sphenoidal Yol they're like these two little mezzanine flaws that make up the rest of the anterior cranial fosser so we've got those superorbital plates we've got the cror plate of the ethmoid bone we've got the sphenoidal Yol and now we've got these lesser wings of the sphenoid the Lesser wings of the sphenoid make up the superior margin of the superior orbital Fisher let's have a look at what that looks like I find it best look on the sagittal plane we're in in the midline here we can see the crystal gy we head out laterally we can see now this here is what's known as the Lesser wings of the sphenoid as we head out laterally you see this fure here is the superior orbital Fisher the Lesser wing of the sphenoid makes up that Superior border of the superior orbital fure let's head medly again and we see these large outcroppings known as the anterior clinoid processes it's easier seen on our axial slice here here are the anterior clinoid processes which are part of those lesser Wings the anterior clinoid processes sit above the optic canal and they are great Landmark to look for when you're looking for the optic Canal if we scroll inferiorly we will see the optic Canal come into view you see how the Lesser Wings lie over that optic Canal now the optic nerve obviously is going to travel through the optic canal and they're going to form the kaym here the optic kaym and this recess here is what's known as a chmatic so those optic nerves wrap around here above the cellat TOA so the Lesser Wings they aren't actually that complicated they're very small they sit above the optic nerve they're separating the optic nerve from the cerebrum here from the anterior cranial fosser so those are the Lesser Wings the greater wings are much more complicated we need to head down inferiorly and we know that the greater Wings make up part of the middle cranial fosser so as I head down inferiorly it's difficult to see the greater Wings in a single plane they've got these concave shapes on the superior surface of the sphenoid bone but it's useful to think of the greater wings of the sphenoid as having three separate surfaces they've got an orbital surface which faces out towards the orbit it makes up the inferior border of the superior orbital fure and the superior border of the inferior orbital fure again it's better appreciated on that 3D model then there's a temporal surface of the greater wings of the sphenoid bone that faces out naturally it's the external surface of the sphenoid bone you'll feel that if you press here on what you think is your temples that's actually the temporal surface of the greater wings of the spinoid and then these concavities here which make up the floor of the middle cranial fosser is the cerebral surface of the greater wings of the sphenoid bone now the cerebral surface is sometimes quite difficult to get your orientation what you want to do is scroll superiorly till you find the hypophysial fosser we know that lateral to the hypothesi AL FASA are those greater wings of the sphenoid bone the cerebral surfaces now there three main foramina in the greater wing of the sphenoid bone that are very important to know and the best way to find the first one which is the fan rundum is by looking at the coronal scan on our coronal slice we can head posteriorly and head towards where our optic nerve is going to come out as we scroll posteriorly we know that the optic nerve runs runs through these lesser wings of the sphenoid bone here you can see the sphenoidal Yol the body of the sphenoid bone and the Lesser wings of the sphenoid bone as we head posteriorly we should see these two parameter coming out here this is the fan rundum you can see it's in the middle cranial fosser now the framan rundum goes anterior to posterior it's like someone looking through binoculars so it's difficult often to see initially on our axial slice it's much easier to see with this coronal slice and we can follow the frame and ranum here into the terop Palatine fosser which will also be a subject of a whole entire Talk itself so once we found the framan rundum on both sides we can go back to our axial slice and find it on the axials you can see it's actually not cut perfectly here but the fan rundum is heading forward here into the terago Palatine fosser now the nerve that goes through the fan rundum is a maxillary division of the trigeminal nerve posterior to the framan rundum as we head down down into these middle cranial fucer we can see a fan forming known as The Fan ovali there are a couple of structures that run through the Fram and oval or Fram and oval the first being the mandibular division of the trigeminal nerve so now we've seen the mandibular division running through the frame and ofal we've seen the maxillary division running through the Fram and rundum and we also have an accessory menial artery running through here as well as the Lesser protal nerve posterior and laterally to the frame and no is a small framan known as a framan spinosum and the framan spinosum has a middle menal artery running from inferior to Superior which will run on the interior surface of the neurocranium as the neurocranium heads up here part this very thin section of bone here which we're going to look at later known as a terion this is a common question that if you fracture this very thin plate here you can disrupt the middle menular artery and get a hematoma forming there so through the freman spinosum is the middle menular artery so I know in these scans on these 2D scans it's difficult to appreciate where the body is where the hypophysial foser Lesser wings and greater wings are and I'd encourage you to take your time going through scans and trying to identify each one of these points now the sphenoid bone anteriorly we've already said has the sphenoethmoidal suture the spheno frontal suture and that spheno frontal suture has an interesting course that I can show you on the 3D model it also interacts with the occipital bone posteriorly as we said when it goes down towards the clus here let me go to the midline on our sagittal scan as the sphenoid comes down towards the clus the occipital bone is here we get a speno occipital synchondrosis it's not always a suture there's a proper Fusion that happens there and then there are two more sutes one being laterally which is our sphenoparietal suture and we get a spenos sosal suture between the sphenoid bone and the squamous portion of the temporal bone which we're going to look at when we look at the temporal bone so the temporal bone at least for me is also a difficult B bone to conceptualize a 3D anatomy And if you ever have the time to sit with a 3D model I'd highly encourage you to take the time looking at the various parts of the temporal bone especially how it interacts with the speno bone I find that very difficult to conceptualize I'm also going to link a document below this video where I show you the anatomy that we've covered in this video give you some pictures of the 3D models label those pictures and you can really spend time appreciating how the bones interact with one another now we can also separate the temporal bone into four different part aamus part A petris Part mastoid part and tanic part and I'm going to leave the tanic part out of this talk we're going to cover that in depth when we look at the inner ear and when we look at high resolution CT of the temporal bone so the squamous part I like to think of the temporal bone as holding the neurocranium like this the squamous part makes up the lateral walls of that middle cranial fosser if we have a look at our coronal CT here you can see the temporal bone cut in its coronal plane and the squamous part of the temporal bone heading up like this it's making the lateral walls of this middle cranial fucer there's an anterior extension here as we come out anteriorly we can see that the temporal bone interacts with the zygomatic bone here and that's a zygomatic process of the temporal bone also coming off the squamous part of the tempal bone the squamous or thin part of the temporal bone making up those lateral walls also has the squamous suture between the parietal bone and the temporal bone and the spenos squamous suture between the sphenoid bone and the temporal bone if we look on our axial scan here we can see the petris part of the tempal bone this is the meat and potatoes of the tempal bone there's a lot going on on the petus part perhaps most prominently is this internal cored artery traveling through the Petra section of the temporal bone through the cored canal heading up superiorly before it Dives forward into that cored sulcus that we looked at earlier that cored artery runs Above This framan Here known as The Fan lerum this irregularly shaped f here which is largely filled with cartilage as we head up more superiorly we can see this Ridge here being formed by the petus part of the tempal bone and within that Ridge we've got the superior petal sinus this Ridge marks the border between the Middle cranial fosser and the posterior cranial fosser and it's known as the aru Eminence let's head down inferiorly now and we can see an opening here known as the internal acoustic meatus that's also part of the petus part of the temporal bone when we're looking at the temporal bone we can also see this indentation here which represents the sigmoid sinus that's carrying blood away from the Confluence of the sinuses away from those transverse sinuses and putting it down towards the jagular fan so if we follow that sigmoid sinus round we can see the jugular Fame in here as it exit the skull base might be easier on the other side here is the jugular foramen right behind the cored artery that's coming into the skull jugular fmen carry in blood away from the skull down there now it's easy to see the mastoid part of the temporal bone we've got these mastoid air cells it's pneumatized bone and as we scroll backwards on our coronal scan we can see the mastoid process coming down like this now the mastoid process is an attachment side for many different muscles on the medial surface here we've got the digastric muscle D meaning two gastric meaning bellies a two bellied muscle where the posterior belly attaches to the medial surface of the mid process here it heads out towards the hyoid bone then wraps down underneath the mandible here on the mastoid process itself we've got an attachment side for the stoco mastoid as well as the splenius capitus and the longism capitus muscles there so four muscles attaching to the mastoid process here and you can see the air cells of the mastoid process here and that inner Groove that we talked about earlier of the sigmoid sulcus comes right next to the mastoid part of the temporal bone and we know that that sigmoid sulcus heads down into the jugular Fen now the jugular fmen will have the jugular vein traveling through it out of the skull exiting the skull it will also have cranial nerves 9 10 and 11 and a posterior menal artery traveling through this Frame and a really important spot on skull base Anatomy so we've now looked at the various parameter within the petus part of the temporal bone we've seen the mastoid part as well as the squamous part as we head up soup superly Superior to that squamous part the squamous suture separates the temporal bone from the parietal bone now the parietal bone is a fairly standard bone there's not much going on with the parietal bone whenever we think of parial we think of parial plura parial parium paral meaning the walls so the parial bones make up the walls of the neurocranium and it's a paired bone as we saw earlier we saw that the parietal bone was separated by these sagittal sutur superiorly we said the coronal suture separates the parietal bone from the frontal bones and that point is known as the bregma that point of intersection posteriorly the parietal bones is separated from the occipital bone by the lamboid suture now there's a Greek letter Lambda and this lamboid suture has the same shape as the Greek letter now this point where the sagittal suture meets the lamboid suture is known as Lambda so we've got bregma we've got Lambda gabella Nason now as we head down we've mentioned before the sagittal sulcus here of the parietal bone where the superior sagittal sinus travels back to the Confluence of the sinuses if we head posteriorly on this coronal scan you will also see that indent there here's the sagittal sulcus for that Superior sagittal sinus now there's two more bony landmarks that I want to mention one is called the terion the terion is this H shaped conglomeration of sutures the one line of the H is made up by the squ suture and the spenos suture the connecting crossbridge of the H is the sphenoparietal suture and then the last line of the H is the coronal suture and the speno frontal suture that region is called the terion a very thin part of bone that we looked at earlier we mentioned earlier that if broken can disrupt the middle menial artery and cause a hematoma there's also something known as the asterion where the Lambda suture separating the parietal bone and the occipital bone meets the parieto mastoid suture now we're going to look at the last bone called the occipital bone it's a unique bone because it interacts directly with the cervical spine so much like some of the other neurocranial Bones the occipital bone can be separated into different parts a squamous part A basil parts and lateral Parts if we start by looking at the squamous part it's the most posterior aspect of the neurocranium it houses the cerebella hemispheres as well as the occipital loes which are separated by these eminences here known as the cruciform eminences the occipital bone the squamous part if we look on the sagittal plane also has what's known as an external occipital protuberance which is an attachment point for the ligamentum Nu the ligamentum Nu is a continuation of the super spinous ligament now as we head down along the screamous part of the occipital bone we're in the midline here we can see the crystal galy here we can see there's a big opening within the occipital bone this opening is known as the fan Magnum remember the occipital bone wraps around the frame and Magnum and this is still part of the occipital bone this is what's known as the basil part of the occipital bone it's called the cus it's where the basil artery runs up anterior to The Ponds this is where the occipital bone articulates or is connected to the sphenoid Bone that's called the speno occipital synchondrosis it's not normally a suture there it's normally fused together the lowest point here the most anterior point on the frame in Magnum is known as the bason the most posterior Point here of the frame and Magnum is the aiston so you've got Inon aiston and bason traveling through the framan Magnum is the medala ofata as well as ascending vertebral arteries paired vertebral arteries that are going to give off anterior and posterior spinal arteries that are going to descend through the Fram and Magnum we can see the Fram and Magnum on our axial slice here and then we can see how the occipital bone articulates with the C1 vertebra these are the occipital condal don't get confused thinking that these are part of the spical vertebrae you can see on Al coronal the occipital Condes almost look like vertebrae this is part of the occipital bone and you can see the occipital Condes articulating with the atlas or the C1 this joint here is what's known as the atlanto occipital joint and these are the lateral atlanto occipital joints here whilst we here we can see a fan running through through the occipital condil this is what's known as a hypoglossal canal and you guessed it the hypoglossal nerve travels through that Canal you can see it almost looks like an eagle with a beak going over the hypoglossal na this is what's known as the jugular tubercle that covers the hypoglossal canal this is what it looks like on an axial slice you can see the hypoglossal canal travels from medial to lateral from posterior to anterior and this sheet of bone overlying the hypoglossal is the jugular tual so we've seen the fan Magnum we've also seen the hypoglossal canal we also have what's known as the jugular forment now the jugular fan is quite difficult to see and at this point we have the sigmoid sinus combining with the inferior petal sinus to form the jugular framan that's going to head down into the neck become the jugular vein now going through that framan we've talked about it before is the jugular vein it's also got the cranial nerves 9 10 and 11 as well as a posterior man artery traveling through it so hopefully this has given you a good idea of how to look at the various different bones within the neurocranium the only way that you can really truly understand this is to go through many scans yourself look at the different sutures and try and name the sutures try and look at the different Fram name the Fram see what goes through the Fram again in that document that I've linked below I will have all of those details you'll be able to test yourself now in the next talk we're going to look at the viscerocranium the facial bones that sh there's some of the bones that we've looked at we'll look at the ethmoid bone again we're going to look at the sphenoid bone with the teroid processes that head out into the face hopefully after these two talks you'll have a great Foundation as to the bones that make up the neuro and viscero Cranium then we can go into more detailed looked at the specific bones don't get worried if you're not sure exactly where the bones are and how they interact with other bones we're going to go through each of these bones individually or at least the most complicated bones so until the next talk I'll see you all there goodbye everybody