Ethmoid Bone

by Darren Salmi, MD, MS

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    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.

    About the Lecture

    The lecture Ethmoid Bone by Darren Salmi, MD, MS is from the course Skull.

    Included Quiz Questions

    1. Crista galli
    2. Cribriform plate
    3. Perpendicular plate
    4. Median plate
    5. Ethmoidal labyrinths
    1. Olfactory nerve
    2. Trigeminal nerve
    3. Oculomotor nerve
    4. Abducens nerve
    5. Hypoglossal nerve

    Author of lecture Ethmoid Bone

     Darren Salmi, MD, MS

    Darren Salmi, MD, MS

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