The Skull - Online Tutor, Practice Problems & Exam Prep

The skull consists of cranial and facial bones, with the cranium protecting the brain and the facial bones forming the structure of the face. Key cranial bones include the frontal, parietal, occipital, temporal, sphenoid, and ethmoid bones. The facial bones include the maxilla, mandible, zygomatic, nasal, lacrimal, inferior nasal conchae, vomer, and palatine bones. Additionally, paranasal sinuses, such as the frontal, ethmoid, maxillary, and sphenoid sinuses, lighten the skull, warm and humidify air, and enhance vocal resonance.

Introduction to the Skull

Start learning the bones of the body. We're going to start with the skull, and the skull is this complex bony structure. It's not a single bone; it is many bones. And to illustrate that, we have this skull over here. We have a side view and a frontal view of the skull, and you can see all the different bones there color coded. Now, pretty soon, you're going to be able to label and name every bone in that picture, and we're going to get you there. Alright. We're going to start off by talking about the cranial bones. The cranial bones are the bones that make up the bony house for the brain. Now I have a big old round head, and that significant roundness of my head is from my cranial bones. So that's because the cranial bones make up this hollow structure. Hopefully, it's not hollow. There's a big old brain in there, but the cranial bones are surrounding that brain, and they're protecting the brain inside.

Next, we're going to go through the facial bones, and the facial bones make up the structure of the face. Alright? Your face is this really complex three-dimensional structure that makes you look like you. Now, I'll be honest, when I was learning the bones of the body, I found the facial bones particularly challenging. That's because the facial bones create this kind of weird three-dimensional structure, and they fit together in this very puzzle-like way that's kind of hard to imagine in your mind's eye. But don't worry. We'll get you there. Alright. We're also going to learn some associated bones. The associated bones are going to be bones that are used for hearing and swallowing. The bones for hearing, these are three tiny bones in your inner ear that connect the eardrum to the inner ear. Now we're not going to learn them while learning about the skull. We're going to learn those when we talk about the special senses. Now for swallowing, we're talking about the hyoid bone. The hyoid bone is this bone in your neck that's the base of the tongue and involved in swallowing. And, even though it's not directly connected to the skull, its function is related to the functions of the skull, so we learn it with the skull.

As we learn about the skull, we're going to learn about the different cavities and sinuses of the skull. These are the spaces in the skull. You have your orbital cavity for your eyes, your nasal cavity inside your nose. You have your sinuses. These are spaces inside some bones of your skull. Those sinuses, if you've ever had a sinus headache or a sinus infection, you probably know where they are.

When talking about the skull, let's talk about what the skull does for you. It has several functions, and here we're breaking it down into five functions. Now, like always, putting an exact number on this is a little difficult because it depends on how you count, but we're going with five. First, we're going to say it protects the brain. To illustrate that, we have a brain here wearing a helmet, and the cranium is really the helmet for your brain. It's there to protect what's inside. If you're doing something extraordinarily dangerous, you might put a helmet on top of that cranium to give it extra protection. But for the most part, your cranium does a pretty good job of protecting the brain. Next, we say it is there to produce facial structures. You look like you do because of the bone structure of your face. To illustrate that, we have a person here, a little cartoon of a person making different faces. Now obviously, it's not just your bone structure that makes you look like you do. You also have skin and muscles on it and lots of your different facial expressions. That's obviously because of moving those muscles. But the underlying structure, the underlying basis of what you look like, that's the shape of those bones. We're going to have some openings in the skull, and those openings will allow you to obtain air and food. You breathe through your nose or through your mouth, and then you have your big old pie hole there that we can see in our illustration, a big old mouth that looks ready to chomp down on a cheeseburger. Well, when you chomp down on the cheeseburger, you're going to chomp down with your teeth. And one thing that your skull does is anchor your teeth. We'll learn about the teeth in the digestive system, but that's a major job of the jaws. Your upper and lower jaw is going to hold those teeth in place. Finally, we're going to say that the skull is there to house your sense organs. Your eyes, your nose, your ears, all these things are in your head, and that's how you experience the world. It's largely through your skull because that's where those really sensitive sense organs are. Alright. With that, now we know what the skull does. Let's go learn the bones.

True or False; if false, select the answer that best corrects the statement.

Associated bones provide a house for the brain.

• A. True, the associated bones make up the cranium. 
• B. False, the associated bones provide the structure of the ear and nose.
• C. False, the associated bones are involved in hearing and swallowing.
• D. False, the associated bones create facial features.

Overview of Cranial Bones

We're going to start learning the bones of the body by learning about the skull. We're going to start with the cranial bones. Now your cranium, that's the round part of your skull that houses your brain, the bones that protect the brain. So we're going to start off just by saying that the cranium is made up of 8 bones, and those bones are going to be connected by sutures. Now, we haven't gone over types of joints yet, but a suture just means that the bones have grown together in a way that they're still separate bone, but they're kind of interlocked, so it's not a movable joint. They're quite firmly together. Now before we go on, I just want to note, we say here 8 bones. They're numbered, however, 1 through 6. That's because there are going to be 2 parietal bones and 2 temporal bones and one of all the other bones. Now finally, let's just orient ourselves to the picture here. We have a side view of the skull with all the bones color-coded. We're going to be focusing on the cranium, these bones in the back. There. Alright. Our first bone that we are going to talk about then is going to be the frontal bone. The frontal bone, well, in blue here, it's here making up the brow ridge, your forehead, up to the top middle of your head. One of those, it's the frontal bone. It's the front of the head. I'm just going to say here it is the forehead bone. Alright. Frontal bone, front of the head, pretty straightforward. Next, we have the parietal bone, and the parietal bone you can see in green here. There are 2 of these and they make up the upper side walls and the top of your head. So I'm going to write here the upper side of your head or upper sides of your head. And parietal, the word comes from Latin meaning wall, and so, it makes up the walls of your head. But the way I remember it is if you make bad decisions in college, then your parents might grab their parietals. Parents grab the parietals. Those are the bones on the

If a patient has a tumor on the pituitary gland, a surgeon will often make an incision in the nose before cutting into which bone to reach the pituitary?

• A. Frontal
• B. Sphenoid
• C. Occipital
• D. Temporal

Damage to which bone is most likely to cause problems with hearing?

• A. Frontal.
• B. Sphenoid.
• C. Occipital.
• D. Temporal.

The Skull Example 2

Our example tells us that in a cleft palate, the roof of the mouth or palate does not fuse properly during development. It says that without surgical correction, a cleft palate can lead to complications surrounding feeding, ear infections, and speech. And we see here a picture of a baby or a young child with a cleft palate, and then ask the question, what bones would you expect may be surgically repaired in the case of a cleft palate? So you may have heard of a cleft palate before or maybe a cleft lip. If that fusion only fails in the front lip part, it's called a cleft lip. If fusion fails going back further into the bones of the roof of the mouth, it's called a cleft palate. So this question really just comes down to what bones make up the roof of the mouth. So what bones are those? Well, there are 2 bones that make up the roof of the mouth or the palate. The first one is that major bone of the front of the face. It holds all your teeth. It makes up the sidewalls of some of your nasal cavity. It makes up the lower border of your eye sockets or your orbital cavities there. What bone is that? That is the maxilla, and it also makes up a major portion of the front part of that hard palate. Now, the second bone that's smaller and makes up the back part of the palate is the palatine bone. The palatine bone is a more complex bone than just that little part in the back of the roof of the mouth, but that's the part you're more likely to get asked about that you know that it's part of the palate and makes up that hard roof of the mouth. So the maxilla and the palatine bone make up the palate. Those are the bones that may need surgical correction in the case of a cleft palate. Alright. With that, practice problems at all. Give them a try.

During a baseball game, the batter hit's a line drive that strikes the pitcher directly in the face breaking a bone. Among the four bones listed, which bone would you expect to be the least likely to be the bone that is broken in this situation?

• A. Zygomatic.
• B. Mandible.
• C. Maxilla.
• D. Lacrimal Bone.

If you are moving the only freely moving bone in the skull, what activity are you doing and what bone are you moving?

• A. Humming; the palatine bone.
• B. Chewing; the mandible.
• C. Crying, the lacrimal bone.
• D. Sneezing, the ethmoid bone.

The Skull Example 3

Our example tells us that the following lists each have at least one bone that does not belong. We need to cross out any bones that don't belong to each list. And we have an image of a frontal image of a skull here with all the bones color-coded if we need help for reference. Alright. So our first list is going to be the bones that contribute to the nasal cavity. So take a look at those four bones. Do any of those not contribute to the nasal cavity? Well, remember we had a little memory device. We said, "my nose smells very interesting perfume extracts." And so as I look at that and I compare it to the letters, well, right away, that "z," there is no "z" there. So the zygomatic, I feel good about crossing out that; not the zygomatic. Alright. So let's check out our bones here. The zygomatic is this cheekbone that has nothing to do with the nasal cavity way off to the side. The ethmoid, the ethmoid, that is this bone that makes up the top part of the internal structure of the nasal cavity. It's also part of your cranium, as well. So that's definitely there. The vomer, the vomer is the bottom part of the nasal septum right there, so that's definitely part of your nasal cavity. And then the maxilla, the maxilla is your upper jaw, these purple bones here that make up the border of your nasal cavity. So feel very good about the rest of them. Let's check out our next list. We have bones that contribute to the orbital cavity. Alright. Take a look at that list. Do any of those bones not contribute to the orbital cavity? Well, we also had a mnemonic device, a little memory tool for this one. We said, "my little I spies pretty fast zebras." Alright. So as I look here, all those letters are in my memory tool, but there is an issue here. This "m" is supposed to be for maxilla, and here we have "d" as the mandible. Remember, the mandible is your lower jaw. It has nothing to do with your orbital cavity. So feel pretty confident that it's not the mandible. Let's just check out our other options. Here, we have the lacrimal. Lacrimal, right, that makes up the inner border of your eye there, that little small pink bone right in here. The sphenoid. Sphenoid was that cranial bone that looks like a bat, but it makes up the back of the orbital cavity there. We can see it in yellow. It also sort of sticks out in your temples right there. And then finally, we had the zygomatic. Well, the zygomatic, we just said was your cheekbones. Your cheekbones make up that lateral border of your orbital cavity. So the rest, definitely part of the orbital cavity. Alright. Our last list here is going to be bones that anchor the teeth. So which of those don't anchor any teeth? Well, the bones that anchor the teeth, we said they both start with "M." They're the maxilla and the mandible, and you could say maxilla and the mandible are for mastication. They're there for chewing. Yeah. So those are the bones that do, but the ethmoid, therefore, definitely does not. Remember the ethmoid, that's this bone of the cranium and also making up the internal structure of the nasal cavity. It doesn't hold any teeth. And then we have the palatine. Well, the palatine does make up the back of your mouth, makes up the roof of your mouth there, but all of the teeth are in the maxilla, not in the palatine bone, so it's not that. Alright. With that, I feel like we found the bones that don't belong in each list. Like always, practice problems to follow. We'll see you there.

One of the occupational hazards of boxing is a deviated septum, where the cartilage of the septum is damaged shifted to one side. What two bones may also be involved in a deviated septum?

• A. The vomer, sphenoid, and ethmoid bones.
• B. The sphenoid and ethmoid bones.
• C. The vomer and sphenoid bone.
• D. The vomer and ethmoid bone.

Which bone creates the lateral wall of the orbital cavity?

• A. Zygomatic.
• B. Lacrimal.
• C. Sphenoid.
• D. Maxilla.

Overview of Sinuses

As we learn the bones of the skull, some structures that you're very likely going to need to know about are the sinuses. Now, sinuses are just air-filled cavities that are lined with mucosa, and mucosa is just a tissue that produces mucus. So, these air-filled cavities are going to be really moist inside. They are going to be found inside of bones, but they're also going to be connected to the nasal cavity. So sometimes, these are called the paranasal sinuses. Now, these are doing a few things for you. First off, they are going to lighten the skull. And by that, I just mean bone is a heavy tissue and air is lighter than bone. So if you have a cavity in the bone that's not filled with bone tissue, but instead it's filled with air, your head is just going to be lighter. And so, to signify that, we have a little image here of some hot air balloons, showing how that makes your skull lighter. Next, we are going to say that they work to warm and humidify the air, and to show that, we have a little stove here with a fire showing it's warming, and then a little humidifier next to it. Now, when you breathe in, you're breathing air down into your lungs, which is really sensitive tissue. So the more surface area that you can get along the way that is warm and moist, well, the more evaporation into that air is going to happen, and just the warmer and more conditioned that air will be when it makes it down into your lungs. And the sinuses are doing some of that for you, as well as the rest of your nasal cavity. Finally, it is going to enhance vocal resonance. And by this, I mean, if you've ever seen like an acoustic guitar, it has this box on the back with a hole in it. That gives an acoustic guitar that nice, loud, rich sound. That box is a resonator box. If you compare that to an electric guitar that's not plugged in when you play it, it really doesn't sound very good. Now that's pretty similar to your voice. And to illustrate this, we have a guy singing here. But, if you've ever tried to talk with a really bad cold where your nasal cavity is all blocked up, you can't use those resonance chambers of the sinuses. And so when you talk like this and you say you have a really nasally voice, it's because you're not getting the resonance of the nasal cavity and of the sinuses. Okay. So let's name our paranasal sinuses here. They're going to be found in these four bones. First off, we have some in the frontal bone, and those are aptly named the frontal sinuses. And we can see here we have a picture of a woman showing the different sinuses that are color-coded. And here we have the frontal sinuses in the frontal bone, that bone of the forehead sort of in your brow ridge right up here. Next, we have the ethmoid bone has the ethmoid air cells, and that's these little marks here in green. Remember, the ethmoid bone, technically a cranial bone, but it makes up a lot of that internal architecture of the nasal cavity. Now, these are called the air cells because you see over here; there are a few of them. They're not just one cavity. The ethmoid air cells are a bunch of smaller little sinuses within this bone. After that, we have the maxillary sinus in the maxilla, and you see over here in purple, filling up a lot of the front of the cheek here, all in here, the maxilla, those bones are hollow. They have these big sinuses in them. Lastly, we have the sphenoid bone has the sphenoid sinus, and you see in yellow here well, remember the sphenoid bone is a cranial bone. It's that bat-shaped bone at the front of the cranium, so all the way in the back of the facial bone. So this is going to be at the back of the nasal cavity. Now to remember these, we have just a real quick little word here. You can say fems. Where are my sinuses? Fems. They are in the frontal bone, the ethmoid bone, the maxilla, and the sphenoid bone. Alright. With that, those are the sinuses. We'll see you in the next video.

The Skull Example 4

Our example tells us that Dimitri is traveling on a plane while suffering from a cold. As the plane takes off, he begins to feel pressure and develops an intense pain just above the medial side of his right eye. Now, he wants to know what might be the source of this pain. So, what do you think? Well, we're in the section on the sinuses, and we have a picture of a skull here showing the sinuses color-coded, so I'm pretty sure the answer is going to have to do with the sinuses. But let's be a little bit more specific than that. What sinus is going to cause pain just above the medial side of the right eye? Well, if you don't remember, we had an acronym to remember the sinuses. We had FEMs. And FEM stands for the frontal sinus, the ethmoid air cells, the maxillary sinus, and the sphenoidal sinus. So which one of those is just above the eye? Well, here, the right side of the skull is right here. We have this sinus right here in blue. That is the frontal sinus. So what might be the source of Dimitri's pain? I'm going to say the frontal paranasal sinus, and you could just say the frontal sinus as well. Just for completeness, let's just label our other sinuses so that we know them. So I'm just going to outline each one here. The ethmoid air cells, those are here in green. Remember those; there're a few smaller ones rather than just one big cavity in the bone. Next, we have the m is for the maxillary sinus. That's these in purple. I'll outline those right in your cheeks there. And then finally, we have the sphenoidal sinuses. Those are here in yellow, and remember the sphenoid bone is that bone of the cranium shaped like a bat in the back of the nasal cavity. And this pain comes from the fact that these are cavities connected to the nasal cavity. And if they're clogged, if the connection is clogged, when you go up in a plane, you have a pressure change, and that can cause a lot of pressure in the sinus if it can't exchange air with the rest of the nasal cavity, and it can hurt like heck. If you've ever had it happen, you know what I'm talking about. Alright. Problems to follow. We'll see you there.

Which of the following bones is both classified as a facial bone and also contains a sinus?

• A. Palatine bone.
• B. Nasal bone.
• C. Frontal.
• D. Maxilla.

Here’s what students ask on this topic:

What are the main functions of the skull?

The skull has several key functions: it protects the brain, forms the structure of the face, provides openings for air and food intake, anchors the teeth, and houses the sense organs. The cranium acts as a helmet for the brain, while the facial bones shape the face. Openings in the skull allow for breathing and eating, and the jaws anchor the teeth. Additionally, the skull houses the eyes, nose, and ears, which are essential for sensory perception.

How many bones make up the cranium, and what are their names?

The cranium is made up of 8 bones: the frontal bone, 2 parietal bones, the occipital bone, 2 temporal bones, the sphenoid bone, and the ethmoid bone. These bones are connected by sutures, which are immovable joints that interlock the bones firmly together, providing a protective casing for the brain.

What are the paranasal sinuses, and what functions do they serve?

Paranasal sinuses are air-filled cavities within the bones of the skull, lined with mucosa. They are found in the frontal, ethmoid, maxillary, and sphenoid bones. These sinuses lighten the skull, warm and humidify the air we breathe, and enhance vocal resonance. By reducing the weight of the skull, they make it easier to hold up the head. The mucosa lining helps to condition the air before it reaches the lungs, and the cavities act as resonance chambers to enrich the quality of the voice.

What bones form the nasal cavity?

The nasal cavity is formed by several bones: the maxilla, nasal bones, sphenoid bone, vomer, inferior nasal conchae, palatine bone, and ethmoid bone. The maxilla forms the sidewalls and the floor of the nasal cavity, while the nasal bones form the bridge. The sphenoid and ethmoid bones contribute to the back and upper parts of the cavity, respectively. The vomer forms part of the nasal septum, and the inferior nasal conchae create folds within the cavity to increase surface area.

What are the differences between the cranial and facial bones?

Cranial bones form the protective casing around the brain and include the frontal, parietal, occipital, temporal, sphenoid, and ethmoid bones. Facial bones shape the face and include the maxilla, mandible, zygomatic, nasal, lacrimal, inferior nasal conchae, vomer, and palatine bones. Cranial bones are primarily involved in protecting the brain, while facial bones are involved in forming the structure of the face, housing the sense organs, and providing attachment points for teeth and muscles.