Ethmoid Bone

00:01 Next we'll look at the ethmoid bone.

00:04 Which is also another complicated bone that lies deep within the skull.

00:08 So if we take off some of those bones and look from a posterior point of view.

00:13 We can see some of its more salient parts.

00:17 In the midline is a median plate.

00:20 That leads to something called the cribriform plate.

00:24 Which has many holes in it and that's essentially what cribriform means.

00:28 There's a vertically oriented projection called the crista galli that serves as an attachment for dura.

00:34 Then there's a perpendicular plate.

00:40 Here again we see the cribriform plate.

00:43 The crista galli.

00:44 The perpendicular plate going opposite direction as the crista galli.

00:49 And in the midline the median plate.

00:52 Then we have the ethmoidal labyrinths.

00:55 Which are the spaces for ethmoidal air cells.

00:58 Which are basically like sinuses.

01:02 Let's take a look at that cribriform plate of the ethmoid bone.

01:06 It's cribriform meaning it has a bunch of tiny openings or foramina.

01:09 And all of those foramina are for the olfactory nerve, and they're coming from the olfactory mucosa of the superior nasal cavity.

01:18 They're going through the cribriform plate to reach the cranial cavity and form something called the olfactory bulb which will then project backwards towards the brain.

01:30 Here we can see the axons of the olfactory nerves going up through the cribriform plate to form the olfactory bulb.

01:39 From a lateral view, we can see how the crystal galley projects upward from the cribriform plate.

01:46 And here we can see it how it sits in the skull.

01:49 And this crista galli again serves as a nice attachment for part of the dura.

01:55 Here we see the perpendicular plate of the ethmoid bone, which is running inferiorly to the crista galli.

02:03 And that's coming down and forming part of the nasal septum.

02:07 It's forming part of the bony septum.

02:12 Here we see the nasal spine of the frontal bone coming down to that same area of the perpendicular plate.

02:18 And that's where the crest of the nasal bones also joined.

02:23 Posterior is where we have the sphenoidal rostrum.

02:26 And inferior to that is the last bone of the bony septum.

02:30 The vomer.

02:32 Anteriorly is where we have the nasal septal cartilage.

02:36 Which gives the outer nose its flexibility.

02:40 Here we see the ethmoidal labyrinth or else air cells.

02:44 And those air cells again serve a similar function as the other pair of nasal sinuses.

02:50 We have them in the anterior, middle and posterior portions.

02:58 Here's a view of the intact skull showing the orbit and we can see that there's a lateral orbital plate also contributing.

03:06 So here we see the lateral nasal wall with its concha or turbinates.

03:11 It's and actually most of these are going to come from the ethmoid bone.

03:14 We have the middle, superior invariably the supreme nasal concha or turbinates.

03:22 The inferior nasal concha or turbinates on the other hand is not part of the ethmoid bone.