[Music] welcome to the easy med channel where medical topics are made easy today we're going to talk about the cranial bones we'll discuss the anatomy and location of each bone as well as important features that you should know for each one the skull is made up of a total of 22 bones eight of those are cranial bones and the other 14 are facial bones that make up the face we're gonna focus on the eight cranial bones in this video these cranial bones make up the cranium which surrounds and protects the brain so as mentioned before there are a total of eight cranial bones i came up with a simple mnemonic that will help you remember the names of each of these bones the mnemonic is eight osseous parts form the skull this mnemonic is good because it will help you remember that there's eight bones that form the skull the names of these bones include ethmoid bone occipital bone parietal bone which there's two of frontal bone temporal bone which there's two of as well and sphenoid bone we're going to walk through the anatomy and location of each of these bones we're going to go in the order of the mnemonic starting with the ethmoid bone the ethmoid bone is colored in red on the diagram you can see that it sits at the roof of the nose in between the orbits or eye sockets let's take a look at a sagittal view of the skull so we can get a better image of what the ethmoid bone looks like so you can see in the central diagram it's highlighted in green and in the bottom image it's highlighted in yellow you can appreciate how the ethmoid bone sits at the roof of the nose in between the two orbits it actually makes up part of the medial aspect of the orbits there are a couple main features to know about the ethmoid bone and we're going to walk through those now first it separates the nasal cavity from the brain it also articulates with the frontal bone and sphenoid bone which we're going to be talking about shortly the skull is made up of different sinuses one of those sinuses is called the ethmoid sinus and it's located in the ethmoid bone rightfully so a couple other features to know about the ethmoid bone include the cribriform plate and the crista galli starting with the cribriform plate this is where the olfactory nerves travel through so it's an important structure to know another key component is the crista galli this is how the brain attaches to the skull without moving around so there's a membrane that surrounds the brain and this membrane attaches to a cell-like structure called the crista galli on the ethmoid bone let's take a look at a picture of what that crysta galli looks like so again we have a sagittal view of the ethmoid bone and there's a little sail structure that comes up at the top of the ethmoid bone and this is known as the crista galli where the membrane around the brain attaches to inferior to the crista galli is where the crimper formed plate lies and again that's where the olfactory nerves travel through the olfactory nerves are involved in the sense of smell so it makes sense they're going to travel through the ethmoid bone since the ethmoid bone sits at the roof of the nose moving on to the occipital bone this is the bone that sits in the back of the skull as shown in green on the image let's take a look at a couple more pictures of the occipital bone the top image shows the posterior aspect of the back of the skull and the bottom image shows the side view of the occipital bone starting with the top image we can see that there's two parietal bones on either side which we're going to talk about next so don't worry about those right now and the bone in the back of the skull is the occipital bone this is a good image because it shows the suture lines around the occipital bone the sutures are what connect the cranial bones of the skull together so the main suture line of the occipital bone is called the lambdoid suture and this primarily connects the occipital bone with the two parietal bones as you can see on both the image on the left as well as the right the lambdoid suture is easy to remember because it's shaped like the symbol lambda the next main feature to know about the occipital bone is the external occipital protuberance this is the bump that you can feel in the back of your skull and it's the location where neck muscles attach to the next important feature to know about the occipital bone is the occipital condyles these are small protuberances at the base of the occipital bone that articulate with the first cervical vertebra or c1 also known as the atlas the final feature we're going to talk about with the occipital bone is called the foramen magnum and to get a better view of this we're going to look down at the occipital bone the foramen magnum is the big hole at the base of the occipital bone where the brain stem travels through moving through the pneumonia we're now going to talk about the parietal bones there are two parietal bones and they sit on either side of the skull they're shown in blue on the image the parietal bones are surrounded by a number of sutures that connect them to other cranial bones starting with the most anterior suture we have the coronal suture and this connects the parietal bones to the frontal bone that we're going to be talking about next the coronal suture is easy to remember because it travels through the coronal plane then we move on to the squamous suture which connects the parietal bones to the temporal bones which we'll be talking about shortly then we move on to the suture in the posterior aspect of the parietal bones and this is that lambdoid suture that we talked about earlier there's one more suture to know with the parietal bones and this is the suture that connects the two parietal bones together to get a better image of this we need to look down at the skull so first we have the two parietal bones then we have the occipital bone which sits in the back of the skull that we just talked about lastly we have the frontal bone which sits in the anterior aspect of the skull which we'll be talking about next so you can see there's a suture that connects the two parietal bones together this is known as the sagittal suture and this is easy to remember because it runs through the sagittal plane and then just for summary we can see that we have the coronal suture and the anterior aspect and this connects the parietal bones to the frontal bone and then we have the lambdoid suture in the posterior aspect this connects the parietal bones to the occipital bone continuing through the mnemonic we're now going to talk about the frontal bone the frontal bone is shown in yellow on the image this makes up the forehead there aren't too many features to talk about with the frontal bone but you can see that it makes up the bulk of the superior aspect of the orbits there's also a foramen which is a hole in the skull located in the frontal bone this is known as the supraorbital foramen because it's above the orbits and this is where the supraorbital nerve travels through lastly we talked about that coronal suture involving the frontal bone which connects it to the parietal bones next we're going to talk about the temporal bones there are two temporal bones and they're shown in orange on the image there's a number of features to know about the temporal bone so we're going to zoom in on the bone first we know from before that the squamous is the suture that connects the temporal bones to the parietal bones the next feature we're going to talk about is known as the zygomatic process this is a projection that comes off of the temporal bone and joins with the zygomatic bone specifically the temporal process of the zygomatic bone this is known as the zygomatic arch or the cheekbone that you can feel the zygomatic bone is one of the facial bones and we'll be talking about that in a different video when we discuss the facial bones the next feature we're going to talk about is the auditory meatus this is a canal within the temporal bone that connects to the inner ear another feature is the mastoid process and this is the location where some of the neck muscles attach to next we have the styloid process which is located at the inferior aspect of the temporal bone this is the location where some of the muscles of the tongue and larynx attach to lastly we have the mandibular fossa and as the name suggests this is where the mandible articulates the final cranial bone is the sphenoid bone and is shown in pink on the image it's actually the only cranial bone that articulates with all the other cranial bones you can't really appreciate it on the side view but it's almost shaped like a butterfly as you can see on the bottom right hand corner of your screen i've got a few other images of the skull that highlight the sphenoid bone in yellow so you can appreciate the shape here are a couple more images of the sphenoid bone the main component to know about the sphenoid bone is known as the cela turcica this is a depression in the body of the sphenoid bone where the pituitary gland sits as you can see highlighted in yellow in that final image there are a few anatomical features to know with the sphenoid bone and they include the greater wing the lesser wing the pterygoid processes and the body the rest of the bones that we didn't label on the image make up the facial bones and they'll be discussed in a different video hopefully this mnemonic and overview helped you with the cranial bone anatomy if you found the video useful make sure to hit the like button and comment down below before you go if you're new to the channel make sure to subscribe so you don't miss out on future videos that make medical topics easy you can find the notes for this video in the easy med blog which will be linked down below in the description thanks for watching and i hope you check out future videos