Ethmoid Bone Overview

Good evening, and welcome to a new anatomy video from Easy Anatomy by Juan Jose Sanchez. Today we will continue with videos about the bones of the skull. We will specifically talk about the ethmoid bone. These bones of the skull, which make up the cranial vault, are eight bones. We are going to divide them into two groups. We are going to talk about two paired bones, that is, there will be four bones in total. I am referring to the two lateral bones. the two parietal bones, and the two temporal bones. These two bones, which are double, will make up the first four bones of the skull. The other four bones are odd-numbered bones. We will talk from anterior to posterior, about the frontal bone, which you can watch in my video on the channel, the sphenoid bone, which you can also watch in the video, and I will soon upload the video about the occipital bone. We make this mid-sagittal section of the skull to be able to see again the frontal bone. the sphenoid bone, the occipital bone, and the ethmoid bone, which is the king of our video today. So this ethmoid bone is going to be made up of three large portions. A really short bone. The first portion is the vertical plate portion. The second portion that crosses this vertical plate is the horizontal plate, forming a kind of cross. And finally, we're going to talk about two lateral masses that hang from the arms, that cross. It's like having a cross and two bags hanging from the arms or, well, it also looks like a scale. This is a diagram of what the ethmoid bone is. So, this is a single bone. It's a central bone that is located posterior to the frontal bone. It's a bone that's important for the central articulation of the skull. It gives it stability and it's quite irregular with respect to its structures. However, it's considered a symmetrical bone because its right half is the same as its left half. Hey, Cormie, and don't forget to like the video. So, we're going to convert this image to a real image now. Elmoid derives from the Greek word ethimoid, in the form of a sieve. because it has the shape of a sieve. Now we're going to see why the Greeks gave it this curious name. So, this is a frontal section of the skull. Here we're basically going to see the vertical plate that I just drew for you in the diagram. This would be the horizontal plate, which is very short. The diagram came out a little longer, but this is it. This is the very short horizontal plate. And these would then be the lateral masses. We're going to start with the vertical plate, which is the shortest and easiest part of the bone. This vertical plate is going to be divided into two parts, an upper portion above the horizontal plate and a lower portion below the horizontal plate. The portion that is found above the vertical plate is a little wider and is what we're going to call the crista galli process. It hasn't been translated yet, but it's more or less like the rooster's comb process, because it really does look like a rooster's comb. This Christogali process serves to articulate or continue with what is the frontal crest and what is the OS of the brain is going to be inserted into it. That is above this horizontal plate of the ethmoid. Below the horizontal plate of the ethmoid we would then have the perpendicular plate of the ethmoid which is like a central septum. What is important about this perpendicular plate? That it is a medial structure. It is in the entire midline of the body and divides both nasal cavities, because see that what is below the hemoid is the nasal cavity into a right and a left. It, this perpendicular plate, articulates with the boomer, and then this boomer with the maxillary bone, and also with the palatine, as we will see later, and it forms what is the central bony septum of the nose. And this central septum then divides the left nasal cavity from the right nasal cavity. and prevents them from having any type of communication. So, these structures are what make up the vertical plate of the smoid. Let's see it in this lateral view. See here the Christian process, how it articulates with what is the frontal crest. And see that between them is the frontal foramen cecum. It is important that you master the frontal bone so that you can understand how the ethmoid articulates. The order of study is always frontal, ethmoid, sphenoid and occipital. That is why I am uploading the videos in that order. So, the one that is above this structure cut here, which is supposed to be the horizontal plate, would be the Christian. and the one that is below, then the perpendicular plate, see how it articulates with the bomber, which is this bone that you see here, it is a reddish color, to form what is the nasal septum, or. Now, in this superior view we zoom in a little bit closer, we see the crista gai, the blind hole that I told you about and this which would be the frontal crest. We are going to talk now about the horizontal plate. which is a plate that is more elongated in the anterior-posterior direction than in the transverse direction. This horizontal plate will have two faces, an upper face which is this one that looks towards the cranial cavity, that is to say, it is part of the floor of the entire anterior cranial fossa together with the orbital plate of the frontal bone. In fact, the orbital plate of the frontal bone articulates with what is this horizontal plate of the ethmoid. So this upper face, which are these 12 stops by the crista galli, will conform or will be formed by a groove, a hollow, a depression, a concavity. The thing is that here you can't see that concavity well. It's called the olfactory canal. The olfactory vulva is located in that concavity. It's a structure of the first cranial nerve, which is the olfactory nerve. Then it's perforated by many holes, which are the olfactory foramina. through which the nasal nerves that come from the nasal cavity to the olfactory bulla enter, carrying the olfactory information from the nasal cavity. So these little olfactory holes, which some books, like the text in the Datarget, say are arranged in three rows in an anterior or posterior direction. Well, these holes are what give this hemoid its squinty appearance. And that's why many authors call this horizontal plate the cribriform plate of the hemorrhoid. As I said, it articulates with the frontal bone and towards the back it articulates with this bone here, which is the sphenoid bone. This is the upper surface of that horizontal plate. But if we look at this view from below, we can see the lower surface of that horizontal plate again. Notice that there are the same gaps through which the olfactory nerves penetrate. This in the center would be the perpendicular plate that is cut. And this would then be, seen from below, the roof, the vault of the nasal cavity, of both nasal cavities. That is the relationship of the lower surface of the horizontal plate. So, well, what you see here would be the part of the vault of the nasal cavities. This that you see here, and this that you see above would be the cribriform plate seen from above. Let's move on to the lateral masses. which are more or less cuboid structures. They have the shape of a dice, a square and therefore they will have six faces. Let's study each of these faces separately. Remember that this is a frontal section. These are the orbital cavities. These are the nasal cavity and what you see here is the oral cavity. This large gap that you see here is the sinuses of the upper jaw. They are called maxillary sinuses. Now, these lateral masses, excuse me for going back a bit, These lateral masses are going to be made up of six surfaces. As I told you, we are going to start first with the external surface or lateral surface. That lateral surface, notice that it is going to be part of the border of the rim, no, of the medial surface of the orbital cavity. So, remember that the external or lateral surface of the lateral mass forms the limit or the medial wall of the orbital cavity. That is why it is also called the orbital plate. Now, in this lateral view we are seeing what is the left ocular cavity and we are seeing it from the lateral to the medial. We can see the orbital plate there, how it articulates with the frontal. With this bone that is the lacrimal or tear duct. It is written correctly in both ways, with a koji. It articulates with the maxilla. With this one that you see here, which is the palatine, and with this one here, which is the sphenoid bone. That would be the external or lateral face. Now we are going to talk about the internal face, which would be the medial face. This internal face forms the lateral wall or most of the lateral wall of each cavity or nasal fossa. It will be formed by two extensions that are the turbinates, the superior turbinate and the middle turbinate. This one that we are seeing here specifically is the middle turbinate. The superior turbinate is not seen in this section. but it is assumed that it is above it. We will see it in another section. You will also find these turbinates in the atlases under the name of nasal concha. So, look at this section, we are seeing a view from the lateral to the medial. This would then be the perpendicular plate of the vertical. We remove it and we find the lateral mass. Remember that we are talking about the internal face of the lateral mass. We are specifically looking at the nasal cavity on the right side, but we are looking at it from the left side, that is, from lateral to medial. This structure that we see above would be the superior turbinate below the cribriform plate and this would be the middle turbinate. There are three turbinates, superior, middle, and inferior. The only ones that are part of the ethmoid are the superior and middle, because the inferior one here is an isolated bone that has nothing to do with the ethmoid. So, between both turbinates we will find the meat uses. This would be the superior nasal meatus. The one that we find between the middle and inferior turbinates is the middle nasal meatus. And the one that we find between the inferior turbinate and what is the roof of the bony palate would be called the inferior nasal meatus. The one that I want you to learn about right now, which is on the inner surface, is the superior nasal meatus. What are these meat uses for? Or why is it important to study them? Because that is where the sinuses, the sinuses of those huos, empty. Remember that these bones of the skull are aerated bones. They are pneumatic bones that have hollow cavities inside. So, specifically in the superior nasal meatus, the posterior hemoid cells empty through this orifice that you see here, which I will explain to you later about what these posterior hemoid cells are. What I want you to notice right now is that this is where the posterior cells empty, only in the superior nasal meatus. So, we continue cutting and in this image we continue here with the superior turbinate. Now we cut here, you can see the cut edge of the middle turbinate and we see this structure that I will explain to you now, which is the unsaform process. We will see it later. What I wanted was for you to see clearly here what the superior meatus and specifically the posterior hemoid cells look like in the mouth. Let's move on to the upper surface now. This is a superior view, don't be scared because the image is strange. Let me explain, this is anterior, this is the crista pituitary gland. This is the cribriform plate seen from above. This would be posterior. This is medial. So, these would be the superior turbinates. This is lateral. This would be the orbital plate. And this would then be superior. This is the superior surface of the hemoid that is perforated by many holes. It is what is known collectively as the ethmoid labyrinth, because it looks like a labyrinth with that little hole. So, this is anterior. These are called anterior hemoidal cells and these posterior ones together are called posterior hemoidal cells. They articulate with what is the ethmoid notch of the frontal bone. You have to go back to the frontal bone so that you understand what this ethmoid notch is. What is important about all this, guys? I want you to notice this circular structure that specifically has the anterior hemoidal cells. That hole is called the infundibulum. Why is this infundibulum important? Well, let me explain. This is an inferior view of the frontal bones. Here the superior surface of these lateral masses of the delmoid would fit perfectly. But specifically this hole that you see here is the hole through which the frontal sinuses empty. This one on the left and this one on the right. They fit. They fit perfectly with this infundibulum. So for the frontal sinus to empty into one of the meat uses that specifically empties into the middle, I'll tell you in advance, it absolutely has to perforate the infundibulum of the ethmoid and through the ethmoid it can reach the monotis medius. So that's why this image is so important. Look at the frontal sinus, we inserted a wire, it then passes through the infundibulum of the delmoid and it reaches the middle meatus. which I remind you was the middle medus that was between the middle turbinate and the inferior turbinate. Now, the lower surface, which would be the one you see here, is going to be formed by the lower edge of the middle turbinate, which is this one, by the middle nasal medus, which is this space that is found between the middle turbinate and the inferior turbinate, and by the apophysis, a seform, which we are going to remember right now. Now, where does this immediate middle part empty. Well... the anterior hemoidal cells empty into this immediate middle part, which you can see how they are emptying here. Here you can see very well how one of them empties into it. The maxillary sinuses empty into it, as you can see here, and in addition to that, the frontal sinus empties into it through the infundibulum. So many structures of these paranasal sinuses empty into it. Now we are going to see this section. This would be the superior turbinate. I remind you, this is the middle turbinate. We cut the middle turbinate and we find the uniform process, a structure that is then found on the inferior surface of each lateral mass, specifically on the interlateral surface of each lateral mass of the ethmoid. The posterior surface is the surface that it uses to articulate with the sphenoid. With the body of the sphenoid, which is this one that you see here in green, it is like a light turquoise. and it also uses it to articulate with the palatine bone, which is this light blue one that you see here. The last surface that we are going to see is the anterior surface. This is a superior view of the orbit. This would be the maxilla. This would be the longest sigmoid bone. This would be the sphenoid bone and this yellow one, of course, the ethmoid. Note that the anterior edge would be this one that it uses to articulate with the lacrimal bone or lacrimal bone as you want to call it. The sutures that will join the hemorrhoid. The hemoid joins with many bones because you see that it is a central bone. The central bones usually join with many bones. Notice that there is a suture that joins it to the frontal bone. It would be the frontoethmoid suture. One that joins it to the upper maxillary sole, which would then be the smoidomaxillary. One that joins it to the palate, which you can see here how it is joining them, which would be the ethmopalatine. And one that joins it to the palate, which would be the ethmobamarian. Here you can see the ethmobamarian very well. We see here the sphenoethmoid, which is the sphenoid with the ethmoid. Here you can see the frontoethmoid. Finally, towards the front, as I told you, it joins to the lacrimal bone. So, that suture here would be the ethmoidolacrimal suture. So, that has been the entire moid video, friends. I hope you liked it. Here I will leave a little circle for you to like, subscribe to the channel and be able to access all the content of it. I will also leave you the links so you can watch the videos on the frontal bone, the orbital cavity, which is also in my video on my channel, the nasal cavity, the parietal bones, and other bones of the skull. Thank you very much for watching the video. Until next time. Yeah!

We are going to divide them into two groups. We are going to talk about two paired bones, that is, there will be four bones in total. I am referring to the two lateral bones.

the two parietal bones, and the two temporal bones. These two bones, which are double, will make up the first four bones of the skull. The other four bones are odd-numbered bones. We will talk from anterior to posterior, about the frontal bone, which you can watch in my video on the channel, the sphenoid bone, which you can also watch in the video, and I will soon upload the video about the occipital bone. We make this mid-sagittal section of the skull to be able to see again the frontal bone.

the sphenoid bone, the occipital bone, and the ethmoid bone, which is the king of our video today. So this ethmoid bone is going to be made up of three large portions. A really short bone. The first portion is the vertical plate portion. The second portion that crosses this vertical plate is the horizontal plate, forming a kind of cross.

And finally, we're going to talk about two lateral masses that hang from the arms, that cross. It's like having a cross and two bags hanging from the arms or, well, it also looks like a scale. This is a diagram of what the ethmoid bone is. So, this is a single bone. It's a central bone that is located posterior to the frontal bone.

It's a bone that's important for the central articulation of the skull. It gives it stability and it's quite irregular with respect to its structures. However, it's considered a symmetrical bone because its right half is the same as its left half. Hey, Cormie, and don't forget to like the video. So, we're going to convert this image to a real image now.

Elmoid derives from the Greek word ethimoid, in the form of a sieve. because it has the shape of a sieve. Now we're going to see why the Greeks gave it this curious name.

So, this is a frontal section of the skull. Here we're basically going to see the vertical plate that I just drew for you in the diagram. This would be the horizontal plate, which is very short.

The diagram came out a little longer, but this is it. This is the very short horizontal plate. And these would then be the lateral masses. We're going to start with the vertical plate, which is the shortest and easiest part of the bone. This vertical plate is going to be divided into two parts, an upper portion above the horizontal plate and a lower portion below the horizontal plate.

The portion that is found above the vertical plate is a little wider and is what we're going to call the crista galli process. It hasn't been translated yet, but it's more or less like the rooster's comb process, because it really does look like a rooster's comb. This Christogali process serves to articulate or continue with what is the frontal crest and what is the OS of the brain is going to be inserted into it. That is above this horizontal plate of the ethmoid. Below the horizontal plate of the ethmoid we would then have the perpendicular plate of the ethmoid which is like a central septum.

What is important about this perpendicular plate? That it is a medial structure. It is in the entire midline of the body and divides both nasal cavities, because see that what is below the hemoid is the nasal cavity into a right and a left. It, this perpendicular plate, articulates with the boomer, and then this boomer with the maxillary bone, and also with the palatine, as we will see later, and it forms what is the central bony septum of the nose. And this central septum then divides the left nasal cavity from the right nasal cavity.

and prevents them from having any type of communication. So, these structures are what make up the vertical plate of the smoid. Let's see it in this lateral view. See here the Christian process, how it articulates with what is the frontal crest. And see that between them is the frontal foramen cecum.

It is important that you master the frontal bone so that you can understand how the ethmoid articulates. The order of study is always frontal, ethmoid, sphenoid and occipital. That is why I am uploading the videos in that order.

So, the one that is above this structure cut here, which is supposed to be the horizontal plate, would be the Christian. and the one that is below, then the perpendicular plate, see how it articulates with the bomber, which is this bone that you see here, it is a reddish color, to form what is the nasal septum, or. Now, in this superior view we zoom in a little bit closer, we see the crista gai, the blind hole that I told you about and this which would be the frontal crest. We are going to talk now about the horizontal plate.

which is a plate that is more elongated in the anterior-posterior direction than in the transverse direction. This horizontal plate will have two faces, an upper face which is this one that looks towards the cranial cavity, that is to say, it is part of the floor of the entire anterior cranial fossa together with the orbital plate of the frontal bone. In fact, the orbital plate of the frontal bone articulates with what is this horizontal plate of the ethmoid. So this upper face, which are these 12 stops by the crista galli, will conform or will be formed by a groove, a hollow, a depression, a concavity. The thing is that here you can't see that concavity well.

It's called the olfactory canal. The olfactory vulva is located in that concavity. It's a structure of the first cranial nerve, which is the olfactory nerve.

Then it's perforated by many holes, which are the olfactory foramina. through which the nasal nerves that come from the nasal cavity to the olfactory bulla enter, carrying the olfactory information from the nasal cavity. So these little olfactory holes, which some books, like the text in the Datarget, say are arranged in three rows in an anterior or posterior direction. Well, these holes are what give this hemoid its squinty appearance.

And that's why many authors call this horizontal plate the cribriform plate of the hemorrhoid. As I said, it articulates with the frontal bone and towards the back it articulates with this bone here, which is the sphenoid bone. This is the upper surface of that horizontal plate. But if we look at this view from below, we can see the lower surface of that horizontal plate again. Notice that there are the same gaps through which the olfactory nerves penetrate.

This in the center would be the perpendicular plate that is cut. And this would then be, seen from below, the roof, the vault of the nasal cavity, of both nasal cavities. That is the relationship of the lower surface of the horizontal plate.

So, well, what you see here would be the part of the vault of the nasal cavities. This that you see here, and this that you see above would be the cribriform plate seen from above. Let's move on to the lateral masses.

which are more or less cuboid structures. They have the shape of a dice, a square and therefore they will have six faces. Let's study each of these faces separately. Remember that this is a frontal section. These are the orbital cavities.

These are the nasal cavity and what you see here is the oral cavity. This large gap that you see here is the sinuses of the upper jaw. They are called maxillary sinuses. Now, these lateral masses, excuse me for going back a bit, These lateral masses are going to be made up of six surfaces.

As I told you, we are going to start first with the external surface or lateral surface. That lateral surface, notice that it is going to be part of the border of the rim, no, of the medial surface of the orbital cavity. So, remember that the external or lateral surface of the lateral mass forms the limit or the medial wall of the orbital cavity. That is why it is also called the orbital plate. Now, in this lateral view we are seeing what is the left ocular cavity and we are seeing it from the lateral to the medial.

We can see the orbital plate there, how it articulates with the frontal. With this bone that is the lacrimal or tear duct. It is written correctly in both ways, with a koji.

It articulates with the maxilla. With this one that you see here, which is the palatine, and with this one here, which is the sphenoid bone. That would be the external or lateral face.

Now we are going to talk about the internal face, which would be the medial face. This internal face forms the lateral wall or most of the lateral wall of each cavity or nasal fossa. It will be formed by two extensions that are the turbinates, the superior turbinate and the middle turbinate.

This one that we are seeing here specifically is the middle turbinate. The superior turbinate is not seen in this section. but it is assumed that it is above it. We will see it in another section. You will also find these turbinates in the atlases under the name of nasal concha.

So, look at this section, we are seeing a view from the lateral to the medial. This would then be the perpendicular plate of the vertical. We remove it and we find the lateral mass. Remember that we are talking about the internal face of the lateral mass. We are specifically looking at the nasal cavity on the right side, but we are looking at it from the left side, that is, from lateral to medial.

This structure that we see above would be the superior turbinate below the cribriform plate and this would be the middle turbinate. There are three turbinates, superior, middle, and inferior. The only ones that are part of the ethmoid are the superior and middle, because the inferior one here is an isolated bone that has nothing to do with the ethmoid.

So, between both turbinates we will find the meat uses. This would be the superior nasal meatus. The one that we find between the middle and inferior turbinates is the middle nasal meatus. And the one that we find between the inferior turbinate and what is the roof of the bony palate would be called the inferior nasal meatus. The one that I want you to learn about right now, which is on the inner surface, is the superior nasal meatus.

What are these meat uses for? Or why is it important to study them? Because that is where the sinuses, the sinuses of those huos, empty.

Remember that these bones of the skull are aerated bones. They are pneumatic bones that have hollow cavities inside. So, specifically in the superior nasal meatus, the posterior hemoid cells empty through this orifice that you see here, which I will explain to you later about what these posterior hemoid cells are. What I want you to notice right now is that this is where the posterior cells empty, only in the superior nasal meatus.

So, we continue cutting and in this image we continue here with the superior turbinate. Now we cut here, you can see the cut edge of the middle turbinate and we see this structure that I will explain to you now, which is the unsaform process. We will see it later. What I wanted was for you to see clearly here what the superior meatus and specifically the posterior hemoid cells look like in the mouth. Let's move on to the upper surface now.

This is a superior view, don't be scared because the image is strange. Let me explain, this is anterior, this is the crista pituitary gland. This is the cribriform plate seen from above. This would be posterior.

This is medial. So, these would be the superior turbinates. This is lateral.

This would be the orbital plate. And this would then be superior. This is the superior surface of the hemoid that is perforated by many holes.

It is what is known collectively as the ethmoid labyrinth, because it looks like a labyrinth with that little hole. So, this is anterior. These are called anterior hemoidal cells and these posterior ones together are called posterior hemoidal cells.

They articulate with what is the ethmoid notch of the frontal bone. You have to go back to the frontal bone so that you understand what this ethmoid notch is. What is important about all this, guys? I want you to notice this circular structure that specifically has the anterior hemoidal cells. That hole is called the infundibulum.

Why is this infundibulum important? Well, let me explain. This is an inferior view of the frontal bones. Here the superior surface of these lateral masses of the delmoid would fit perfectly.

But specifically this hole that you see here is the hole through which the frontal sinuses empty. This one on the left and this one on the right. They fit. They fit perfectly with this infundibulum. So for the frontal sinus to empty into one of the meat uses that specifically empties into the middle, I'll tell you in advance, it absolutely has to perforate the infundibulum of the ethmoid and through the ethmoid it can reach the monotis medius.

So that's why this image is so important. Look at the frontal sinus, we inserted a wire, it then passes through the infundibulum of the delmoid and it reaches the middle meatus. which I remind you was the middle medus that was between the middle turbinate and the inferior turbinate. Now, the lower surface, which would be the one you see here, is going to be formed by the lower edge of the middle turbinate, which is this one, by the middle nasal medus, which is this space that is found between the middle turbinate and the inferior turbinate, and by the apophysis, a seform, which we are going to remember right now.

Now, where does this immediate middle part empty. Well... the anterior hemoidal cells empty into this immediate middle part, which you can see how they are emptying here.

Here you can see very well how one of them empties into it. The maxillary sinuses empty into it, as you can see here, and in addition to that, the frontal sinus empties into it through the infundibulum. So many structures of these paranasal sinuses empty into it. Now we are going to see this section.

This would be the superior turbinate. I remind you, this is the middle turbinate. We cut the middle turbinate and we find the uniform process, a structure that is then found on the inferior surface of each lateral mass, specifically on the interlateral surface of each lateral mass of the ethmoid. The posterior surface is the surface that it uses to articulate with the sphenoid. With the body of the sphenoid, which is this one that you see here in green, it is like a light turquoise.

and it also uses it to articulate with the palatine bone, which is this light blue one that you see here. The last surface that we are going to see is the anterior surface. This is a superior view of the orbit.

This would be the maxilla. This would be the longest sigmoid bone. This would be the sphenoid bone and this yellow one, of course, the ethmoid. Note that the anterior edge would be this one that it uses to articulate with the lacrimal bone or lacrimal bone as you want to call it. The sutures that will join the hemorrhoid.

The hemoid joins with many bones because you see that it is a central bone. The central bones usually join with many bones. Notice that there is a suture that joins it to the frontal bone. It would be the frontoethmoid suture.

One that joins it to the upper maxillary sole, which would then be the smoidomaxillary. One that joins it to the palate, which you can see here how it is joining them, which would be the ethmopalatine. And one that joins it to the palate, which would be the ethmobamarian. Here you can see the ethmobamarian very well.

We see here the sphenoethmoid, which is the sphenoid with the ethmoid. Here you can see the frontoethmoid. Finally, towards the front, as I told you, it joins to the lacrimal bone.

So, that suture here would be the ethmoidolacrimal suture. So, that has been the entire moid video, friends. I hope you liked it.

Here I will leave a little circle for you to like, subscribe to the channel and be able to access all the content of it. I will also leave you the links so you can watch the videos on the frontal bone, the orbital cavity, which is also in my video on my channel, the nasal cavity, the parietal bones, and other bones of the skull. Thank you very much for watching the video.

Until next time. Yeah!

Transcript for:Ethmoid Bone Overview

Transcript for:
Ethmoid Bone Overview