BIO 176: Human Anatomy Lab Bone Practical: Lecture

Bone-Axial Skeleton

Speaker: Heidi Peterson

What you will see in the following presentation are all of the bones and features and markings you will need to know for your upcoming practical. We are going to start with the skull. On the skull you will see an anterior view, which is like looking at somebody face to face. On the anterior view the use of your regional terms is going to be necessary. You learned them for a reason and they are going to help you with bones.

The first bone you are going to see is your forehead, but it is actually called the frontal bone. The next bone you see is the nasal bone. It also forms the bridge of your nose. You might know it as the cheek bone, but anatomically correct it is called the zygomatic. If you feel in between your two nostrils it might seem strange, but you are going to find a bony protuberance that is called the vomer. The vomer is the bone that gives shape to your lip. That little frenulum comes from the vomer.

Also in the skull you will find two big jaw bones. The top jaw bone is the Maxillae. And the bottom jaw bone is the Mandible. There will be features on each of these bones but we will talk about those in just a bit. Starting with the markings or features you will see a circle around something above the orbit of your eye. Anything that is above something anatomically is called superior or supra. So what you are looking at is a hole or foramen so put it all together and it is the superior orbital foramen. What you see next is the glabella. The glabella is right between your eyes. It is often used for identification purposes to age a skull. The more closed it is the older a person is. Right below the glabella and right below the orbit, and again using our regional terms is another hole. Holes are foramens, so it is the infraorbital foramen. If you put it all together, the last little thing we are going to see at the bottom there on the mandible you will find another hole, the mental foramen. Your chin is your mental area, so again you can see how your regional terms will help you. An overview of this again, look for the frontal bone or your forehead. The nasal bone or the bridge of your nose, your cheek bone or your zygomatic, the vomer just like you are picking your nose, the maxillae; the top jaw, the mandible; the bottom jaw, the mental foramen, the infraorbital foramen, the superior orbital foramen, and the glabella.

If we look at the next view of the skull, the lateral view, we are going to see a lot of the same bones. So I would be ready to be able to label all of the bones that you see on every view of the skull. The first bone you are going to see on the lateral view of the skull is the parietal bone. The parietal bone makes up the Sagittal suture when it comes together at the top of your skull. The next bone on the side is the temporal bone. Right where your temple is and having lots of processes and foramens on this bone. From the side you can also see a good view of the cheek bone, zygomatic. If you look at that closely the zygomatic is like the apple of your cheek, and we are going to learn about the zygomatic process which is the arch of your cheek. Looking at the features we are going to run first suture. Sutures are where two bones come together. It is a fibrous connective joint and it is called a suture, cuz it looks like where the bone has been sewn. The first suture we see is between the temporal and parietal bones and has the name squamosal or squamous suture. Back to the temporal bone and the features or markings you would find on it includes the zygomatic process, the arch of your cheek. The hole that you see is the

Page 1 of 4 BIO 176: Human Anatomy Lab Bone Practical: Lecture same hole you can stick your finger or q-tip in. It is the most interior part, and it is called the external acoustic meatus. One of the reasons you don’t want to put a q-tip too far into your ear is because you will hit brain, brain is right on the other side of that. In the lateral view, you will also see on the temporal bone, the mastoid process. If you take your thumbs and go right behind the lobe of your ear you will see/feel a big bump, that big bump is the mastoid process. If you push your thumb in a little farther, it might start to hurt, that’s because the next process you felt is the styloid process. We will run into a lot of styloid processes as styloid just means sharp pointy piece of bone, at least in layman’s terms. So the last feature you are going to see on the skull is part of the mandible called the ramus. So again we have bones and markings on that lateral view, ramus, zygomatic process, squamosal suture, styloid process, mastoid process, external acoustic meatus. And bones that include, the zygomatic, parietal, and temporal.

We are now going to take the skull and turn it over. When we turn it over it is an inferior view. The inferior view of the skull includes the mandible being removed so you just see the underpart of the maxillae. You know it is the maxillae because you can see teeth. The big hole that you see is also a landmark to show that you are inferior on the skull. So what we can see is the maxillae where all the teeth are and right behind is circled is the palatine bone. I always remember it because it looks like the McDonald’s arches. The little point is where the uvula hangs off of that, that is the soft tissue uvula so that is also a landmark and you know where it is in your body.

In the skull from the bottom we can also see a really good view of the occipital bone. This is the bone that rests on your atlas and axis and helps you to nod your head yes and no. The little foramen that you see right behind the two front teeth is called the incisive foramen. It is called the incisive foramen because it sits right behind the incisors. So on this skull, we have the incisive foramen, the palatine bone, the occipital bone, and the big hole you see is the foramen magnum. And foramen magnum is actually Greek for big hole.

One of the last views of the skull we will look at is the superior view. The superior is really easy to see some of the bones of the top of the skull. What you see first is the frontal bone. And if you look at the picture you can see where the nose would be because you can see the ridge of the nasal bone, so the anterior part of the skull is at the top of the picture. The posterior part is in the back of the picture. We can also see a really good view of the parietal bone. And two really nice sutures, again where two bones come together. We have the coronal suture where the frontal and parietal bones come together, and lastly the sagittal suture where the parietals come together.

The next view of the skull we are going to look at is the posterior view. On the posterior view we see the back part of the parietal bone. If you haven’t noticed by now, the parietal bone is one of the largest bones in the skull being able to be seen on a superior, lateral, and posterior view. This posterior view also gives us, another nice view of the occipital bone. You see the kind of triangular shape? That occipital bone leads us to the sagittal suture where the two parietals meet and the sagittal suture leads us right into the last suture you need to know which is the lamdoidal suture. I always remember it because it looks like a triangle and just like “Revenge of the Nerds,” Netflix or google it if you haven’t seen it, look up Lambda, Lambda, Lambda, that was the name of the fraternity.

Page 2 of 4 BIO 176: Human Anatomy Lab Bone Practical: Lecture

The last view of the skull we have an internal view. The internal view means that we have removed the top of the skull which is called the calvaria. When the calvaria is removed we see the cranial floor or base. And internally we are going to find some very unique looking bones. The first bone or the most anterior bone you will see actually makes up the top portion of your nasal cavity. It is called the ethmoid bone. Right behind it is a bone called the sphenoid bone. There are two features you will find internally one is the crista galli, it looks a little bit like a shark’s fin and sticks up right off the ethmoid. The other feature you will find is the sella turcica. The sella turcica is actually where your pituitary gland sits, and since the pituitary gland is such an important part of your glandular system it is very well protected. Right in the middle of your brain in a little tiny Turkish saddle, or sella turcica. So crista galli, sella turcica, the ethmoid, and the sphenoid, and one can’t fail to see, the big hole or the foramen magnum. This is where you spinal cord comes out and on either side of the hole is where you would find the condyles that sit on your atlas.

Your skull should not move, but we do have one movable part, and that’s the mandible. If any other part of your skull is moving you should probably go to the hospital. On the mandible you will see the feature called the body. You will also see the ramus. The difference between the two is that the body contains all of the teeth and the ramus is the angle of your jaw. So lastly we have another hole. Holes are foramens and again we see another view of the mental foramen.

Moving down to see the skull and the axial skeleton as a whole we see lots of parts. You see ribs. You actually see parts of the arms. You see the cervical spine extending up into the skull, and right under the mandible is a bone that is freely moveable. It is the only freely moveable bone in your body. It is called the hyoid bone. And it sits right above your larynx. It is also one of the bones that is most easily broken. So if someone were to come in with a broken hyoid it is usually due to one of two causes; strangulation or clothes-lining. It is actually one of the most common injuries here in southern Iowa due to ATV accidents. So the hyoid bone. Right under the hyoid bone you would see what you might know as your breast bone. The breast bone’s correct term is sternum. And right off the sternum a little xyphoid process. And we are going to see that in the very last slide.

Right before on either side of the sternum you will find the rib cage. The ribs are actually divided up by how they attach to the sternum itself. True ribs are ribs one through seven have an individual cartilaginous attachment to the sternum. And if you look closely at the slide you can see individual cartilage attaching ribs one through seven. Ribs eight, nine, and ten, are called False ribs for a reason. They sneak up with the cartilage of rib number seven not having an individual attachment or direct attachment to the sternum. Lastly you will see two ribs called the Floating ribs. Ribs eleven and twelve. And just a little fun fact, if you were born in the late 1800s or the Victorian era, lots of times those two ribs were removed so the corset would fit even tighter. It is how some women and men got fourteen to sixteen inch waists. Last but not least on the axial skeleton you will see a feature hanging off the sternum. It is cartilaginous when we are young but as we age it gets more ossified. Ossified is the process of making cartilage into bone. It is called the xyphoid process and it is a common landmark for a lot of health occ students learning CPR.

Page 3 of 4 BIO 176: Human Anatomy Lab Bone Practical: Lecture

The next slide you will see is the hyoid bone on its own. And if you look really closely it resembles a little tiny mandible. You can kinda see the body and the ramus, but we are lucky it doesn’t have teeth.

Moving on in the axial skeleton you will find types of vertebrae. We have cervical vertebrae, thoracic vertebrae, and lumbar vertebrae. They all have the same basic parts, I will only show you on a test the individual parts on the middle vertebrae in the picture, called a thoracic vertebrae. But let’s talk about that cervical vertebrae, if you look at it you will see some distinct features against the other two. You see that in the two features that come off of the vertebral body holes in them. Those holes are actually for the carotid arteries as they come up into your brain. You also see that the spinous process is or the very back part the part that points to the down of the pictures is bifurcated. Bifurcated means that it has two ends. It looks different than the next vertebrae we’ll see. That is the thoracic vertebrae and to me it has always looked a little like a giraffe. If you look at where the body is or the most superior portion of that bone, you can see the two little horns that stick out and its long neck. Last but not least is the biggest vertebrae, it is called the lumbar. And if you actually were to turn it around it looks a little bit like a moose. So we have cervical, thoracic, and lumbar vertebrae. You do not have to know the specific types of vertebrae, such as thoracic 5 or lumbar 7 but I would be able to distinguish between the 3 types of vertebrae on the test and that is how the test question will be asked, name the type of vertebrae.

There are two special vertebrae you need to know for the test. They are the first two cervical vertebrae. They are commonly called C1 and C2. But you might know them by their other names the Atlas and the Axis. If we look at the atlas and the axis, they are telling you exactly what they do. Atlas was the Greek god that held the world on his shoulders, and your atlas holds your head onto your body. The axis has a little piece that sticks out called the dens and it is because of this dens that the axis can turn on the axis. So if you want to say yes, it is because of your atlas, and if you want to say no it is because of the axis.

Last but not least, we will see the parts of the vertebrae. And the parts of the vertebrae include again, a hole, that hole is for your spinal cord called the vertebral foramen. Right anterior to that is the vertebral body. On either side of the foramen, you will find the transverse processes. And last but not least is the spinous process. Those are the little bumps you can feel when you run you hand down someone’s back. At the bottom of the spine you will find a whole bunch of vertebrae that looked squished together. Those squished together vertebrae are you sacrum. And hanging off the sacrum which you will not see a picture of are three to four little bones called the coccyx. You might call the coccyx your tailbone, and you never know what might be a bonus question or extra credit. Hint, Hint.

© Heidi Peterson and Indian Hills Community College

Page 4 of 4