Skull: Introduction

by Darren Salmi, MD, MS

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    00:01 Let's start a discussion of head anatomy by focusing on the bones of the skull.

    00:08 So here we have a lateral view and a superior view.

    00:13 And together, the bones of the skull can be divided into a neurocranium, because they're the bones that essentially house the brain and then a visceral cranium, which are more like the bones of the face.

    00:29 In terms of individual bones, the first bone we see here anteriorly is the frontal bone.

    00:36 Then we see a bone in the area of the nose called the nasal bone that will be attaching to cartilage, more anteriorly.

    00:43 We can see a little bit of the lacrimal bone here and lacrimal refers to tears.

    00:48 So this is a bone that's going to have a duct for the passageway of tear fluid.

    00:53 We can see the outer portion of the sphenoid bone which has a very complicated shape internally.

    01:00 We see the maxilla and the zygomatic bone in the area of the cheeks.

    01:07 Then we have the jaw bone, which we call the mandible.

    01:11 Very complicated looking bone called the temporal bone.

    01:15 And then most posterior in inferiorly, we have the occipital bone and forming a large part of either side of the skull, or the parietal bones.

    01:28 Now, there are some features that we're going to point out such as the zygomatic arch, which isn't actually a distinct bone.

    01:36 It's actually an arch formed from parts of two different bones, both the zygomatic bone and the temporal bone.

    01:44 We also see this pointy projection here coming off of the temporal bone that we call the styloid process, a more rounded projection off the temporal bone that we call the mastoid process.

    01:57 And then also an opening in the temporal bone called the external acoustic meatus.

    02:02 And as the name implies, this is going to be the passageway for sound to travel.

    02:08 There's also a bump or projection on the occipital bone.

    02:13 That's a landmark known as the Inion.

    02:17 If we swing around to an anterior view, we see the frontal bone most prominently.

    02:23 We also see the nasal bones pretty well where they would attach to the nasal cartilage, a little bit of the lacrimal bone, and pretty much all of the maxilla here.

    02:34 We also see a large portion of the mandible or the jaw, a little bit of the zygomatic bone, a little bit of the sphenoid bone, and only a tiny amount of the palatine bone which can be very deep inside the skull.

    02:48 We also see another very deep bone called the ethmoid bone through the opening of the nasal cavity.

    02:55 We don't see much of the temporal bone because it's off to the side.

    02:59 Nor do we see much of the primal bone because it's also very laterally oriented.

    03:06 The bones of the skull are largely formed by non movable joints that we call sutures.

    03:13 The first suture here between the frontal and parietal bones lies in the coronal plane, hence we call it the coronal suture.

    03:22 We also have the suture between the temporal bone in the parietal bones called the squamous suture.

    03:28 And we call it that because the flat part of the temporal bone is called the squamous portion.

    03:35 We also have a suture between the occipital bone and parietal bones that vaguely resembles the Greek lambda character.

    03:43 So it's called the lambdoid suture.

    03:46 And then in the midline, running in the sagittal plane between the left and right parietal bones is the sagittal suture.

    03:54 We also have landmarks such as the bregma, between the coronal and sagittal sutures, and the lambda between the lambdoid and sagittal sutures.

    04:05 And these landmarks during development, were actually fairly soft areas and they were the soft spots on an infant skull known as the anterior and posterior fontanelles.

    04:16 Speaking of development, there was also a suture between the left and right parts of the frontal bone called the frontal or metopic suture.

    04:23 It's usually the first one to fuse and often disappears, but sometimes remnants of that metopic suture can be seen in the frontal bone.

    04:34 There are some smaller sutures that are more descriptive in their names, such as the suture between the frontal and sphenoid bone called the sphenofrontal.

    04:43 We also have a small one between sphenoid and parietal called sphenoparietal.

    04:48 And then a small one between the squeamish portion of the temporal bone and the sphenoid called the sphenosquamous.

    04:55 Further back in the area of the mastoid, we have the parietal mastoid and occipitomastoid.

    05:03 Where all of these small sutures meet in the sphenoid area is also a landmark called the pterion and a similar one in the mastoid area is called the asterion.

    About the Lecture

    The lecture Skull: Introduction by Darren Salmi, MD, MS is from the course Skull.

    Included Quiz Questions

    1. Maxilla
    2. Temporal
    3. Occipital
    4. Sphenoid
    5. Parietal
    1. Coronal
    2. Squamous
    3. Lamboid
    4. Lambda
    5. Transverse
    1. Mandible
    2. Frontal
    3. Sphenoid
    4. Nasal
    5. Lacrimal

    Author of lecture Skull: Introduction

     Darren Salmi, MD, MS

    Darren Salmi, MD, MS

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