Description

 
This video is about the neurocranium Anatomy
Bones of the skull:
Neurocranium: forms the protective case around the brain
Viscerocranium: forms the facial skeleton

Neurocranium:
Skullcap (calvaria):
Frontal bone – os frontale
Parietal bones (paired) – ossa parietalia
Occipital bone – os occipitale

Cranial base (basis cranii):
Temporal bones (paired) – ossa temporalia
Sphenoid bone – os sphenoidale
Ethmoid bone – os ethmoidale

Frontal bone
Coronal suture – sutura coronalis
Supraorbital margin – margo supraorbitalis
Supraorbital notch – incisura supraorbitalis
Frontal notch – incisura frontalis
Zygomatic process – processus zygomaticus
Frontal eminence – tuber frontale
Superciliary arches – arcus superciliares
Glabella
Frontal crest – crista frontalis
Groove for superior sagittal sinus – sulcus sinus sagittalis superioris
Temporal lines – lineae temporales (also on parietal)
Lacrimal fossa – fossa glandulae lacrimalis
Trochlear fovea/spine – fovea trochlearis / spina trochlearis
Nasal spine
Ethmoidal grooves (anterior/posterior) – sulci ethmoidales anterior et posterior
Frontal sinus – sinus frontalis

Parietal bones
Sagittal, coronal, lambdoid, squamous sutures
Angles: frontal, occipital, sphenoidal, mastoid – anguli frontalis, occipitalis, sphenoidalis, mastoideus
Parietal eminence – tuber parietale
Parietal foramen – foramen parietale
Grooves: superior sagittal sinus, sigmoid sinus, middle meningeal artery – sulci sinus sagittalis superioris, sigmoidei, arteriae meningeae mediae
Temporal lines (also on frontal)

Occipital bone
Foramen magnum
Occipital condyles
Hypoglossal canal – canalis nervi hypoglossi
External/internal occipital protuberance – protuberantia occipitalis externa/interna
External occipital crest – crista occipitalis externa
Nuchal lines – lineae nuchales suprema, superior et inferior
Cruciform eminence – eminentia cruciformis
Cerebral/cerebellar fossae – fossae cerebrales et cerebellares
Clivus
Pharyngeal tubercle – tuberculum pharyngeum
Sinus grooves: transverse, occipital, sigmoid, superior sagittal – sulci sinuum
Inferior petrosal sinus groove – sulcus sinus petrosi inferioris
Jugular notch – incisura jugularis, intrajugular process – processus intrajugularis
Sutures: lambdoid, occipitomastoid; spheno-occipital synchondrosis

Temporal bone
Squamous part:
Zygomatic process – processus zygomaticus
Mandibular fossa – fossa mandibularis, articular tubercle – tuberculum articulare
Supramastoid crest – crista supramastoidea

Tympanic part:
External acoustic meatus – meatus acusticus externus
Tympanic ring – anulus tympanicus
Petrotympanic fissure

Petrous part:
Apex – apex partis petrosae
Arcuate eminence – eminentia arcuata, tegmen tympani
Trigeminal impression – impressio trigeminalis
Grooves: greater/lesser petrosal nerves, superior/inferior petrosal sinuses
Internal acoustic meatus – meatus acusticus internus
Subarcuate fossa – fossa subarcuata, jugular notch – incisura jugularis

Mastoid part:
Mastoid process – processus mastoideus, mastoid notch – incisura mastoidea
Groove for occipital artery – sulcus arteriae occipitalis
Stylomastoid foramen – foramen stylomastoideum
Styloid process – processus styloideus
Facial canal – canalis facialis

Sphenoid bone
Body – corpus ossis sphenoidalis, sella turcica with hypophyseal fossa, dorsum sellae, clinoid processes, tuberculum sellae
Prechiasmatic sulcus – sulcus chiasmatis, carotid sulcus – sulcus caroticus

Wings:
Greater wings – alae majores: foramina rotundum, ovale, spinosum
Lesser wings – alae minores: optic canal – canalis opticus
Superior/inferior orbital fissures – fissurae orbitales

Pterygoid processes – processus pterygoidei
Medial/lateral plates – laminae medialis et lateralis
Pterygoid hamulus – hamulus pterygoideus, pterygoid/scaphoid fossae
Sphenoidal crest – crista sphenoidalis, conchae – conchae sphenoidales, sinuses – sinus sphenoidales, rostrum

Ethmoid bone
Cribriform plate & foramina – lamina / foramina cribrosa, crista galli
Perpendicular plate
Ethmoidal labyrinths – labyrinthus ethmoidalis (ethmoidal cells: anterior, middle, posterior)
Superior/middle nasal conchae – conchae nasales
Uncinate process
Orbital plate – lamina orbitalis
Ethmoidal foramina: anterior/posterior – foramina ethmoidalia

Transcript

Introduction
0:00
The human skull consists of 22 bones, which, in adults, are mostly connected together through
0:06
strong joints, known as sutures. At first glance, the skull can appear as a single unit,
0:12
but as complex as we are, we actually divided the skull into two regions, called the neurocranium,
0:18
which surrounds the brain, and the viscerocranium, which forms the face.
0:23
In this video, we’ll go through all the bones of the skull that makes up the neurocranium,
0:28
and talk about their landmarks, surfaces, and their function. Then, go through all of these
0:33
tiny openings, called foramina, which serve as passageways for nerves and blood vessels. And then
0:39
in the next two video, we’ll go through the bones of the viscerocranium and the joints of the skull.
0:44
Intro: Hey everyone, my name is Taim.
0:46
I’m a medical doctor, and I make animated medical lectures to make different topics in medicine
0:50
visually easier to understand. If you’d like a PDF version of this presentation, you can find it on
0:55
my website, along with organized video lectures to help with your studies. Alright, let’s get started
Bones of the Skull
1:00
As we said earlier, the bones of the skull are divided into two systems, the neurocranium and
1:05
the viscerocranium. Viscerocranium is a collection of bones that make up the face skeleton, and it’s
1:12
all of those bones you see here, the maxilla, zygomatic bone, palatine, lacrimal, nasal bones
1:18
and so on. We’re not going to talk about those in this video, because in this video we will
1:22
focus on the other part of the skull, which is the neurocranium. Now the neurocranium form the shape
1:29
of the head and it protect the brain. To make this easier, we generally
1:34
subdivide it into the bones of the skullcap, which consists of the parietal bone,
1:38
frontal bone and the occipital bone, and we have the bones of the cranial base, the floor of the
1:43
skull basically. And these are the temporal bone, sphenoid bone and the ethmoidal bone.
1:49
Just a side note, notice that some bones have the number 2 after them,
1:53
that means we have two of those bones in our head. So if you go ahead and count
1:57
all of those bones, you’ll get 22 bones. Alright? Awesome, now we’re going very detailed here. My
Bones of the Skull Cap
2:04
goal is to make you an expert in bone anatomy. So let’s start with the bones of the skull cap.
2:09
And again they consist of one frontal bone, in the front, two parietal bones on either side of
2:14
the head, and one occipital bone on the backside. So let’s do the parietal bone first. The parietal
Parietal Bone
2:21
bones are those bilateral skull bones that form the superior and lateral walls of the
2:26
cranium. So here we have a right and a left one, with the left highlighted.
2:31
Alright my goal is to give you everything you need to know regarding each bone,
2:31
so this video is going to very detailed, with the sole purpose of teaching you everything
2:31
you need to know regarding each bone. The parietal bone has a frontal border
2:33
which connects to the frontal bone, forming the coronal suture.
2:37
We got a sagittal border, which connects to the contralateral
2:40
parietal bone, forming the sagittal suture. We got the occipital border, which connects
2:46
to the occipital bone, forming the lambdoid suture And we got the Squamous border, which connects to
2:51
the temporal bone, and forms the squamous suture. The parietal bones also has some angels,
2:58
the angle towards the frontal bone is called the frontal angle, back there is the occipital angle,
3:03
towards the sphenoid bone is the sphenoid angle, and then we got the mastoid angle,
3:08
Alright, let’s go a little bit more detailed. These bones are really cooler than they look like.
3:12
So the parietal bone has an internal surface, facing the meninges and the
3:16
brain, and an external surface. Now, focus on the internal surface
3:21
for a moment. We can find the groove for the superior sagittal sinus. This groove is just,
3:26
it contains the superior sagittal sinus, which is one of the major dural venous sinuses we have
3:32
in the brain, basically large veins that drain the brain from blood. I’ve got a video on those
3:37
veins if you’re not familiar with it. But we can also find the groove for the sigmoid sinus,
3:42
which is another large vein in the brain, part of the dural venous sinuses.
3:46
Apart from that we can also find some impressions, meaning grooves along the
3:50
inner surface of the parietal bone, that contain the middle meningeal artery and its branches,
3:55
Alright let’s look at the external surface. This one is a bit special,
4:00
you see those two lines over on the lateral surface? The upper one is called the Superior
4:05
temporal line, which provides an attachment site for the temporal fascia. Just below it
4:10
is the inferior temporal line, which provides an origin site for the temporalis muscle and forms
4:15
the posterosuperior boundary of the temporal fossa. Then we got the Parietal Eminence. This
4:21
is the area of the parietal bone where its convexity is at its maximum, meaning this is
4:26
the highest curved part of the parietal bone. In some individuals, the distance between the
4:32
parietal eminences of the right and left parietal bones represents the maximum width of the cranium.
4:38
Then we can see a tiny little hole up here, called the parietal foramen. The parietal
4:44
foramen allows for the passage of the parietal emissary vein. Emissary veins are the veins that
4:49
connect the extracranial venous system with the intracranial venous sinuses, so it just
4:55
connects the veins on the outside of the skull, with the veins of the inner side of the skull,
4:59
through this opening. And in some individuals, the parietal foramen may only be present on
5:04
one side or may be absent bilaterally. Ok, so – that’s it for the parietal bone.
Frontal Bone
5:10
Hope it made sense. Let’s do the frontal bone now. The frontal bone is an unpaired, flat bone that
5:17
forms the forehead. Back here we have the parietal margin, which connects the frontal bone with the
5:22
parietal bone, to form the coronal suture. And then we have a Supraorbital margin, which is the
5:28
superior border of the orbit. And if we remove the left parietal bone and look at the frontal bone
5:33
from the inside, we can see the sphenoidal margin, this is where the frontal bone meets the greater
5:39
wing of the sphenoid bone. Makes much more sense for me to study the bones once I have a general
5:43
idea about the margins. Alright. Let’s hold the frontal bone, and pull it out. We’ll see this.
5:49
Now, because the frontal bone forms the forehead, parts of the orbit and parts of the nose,
5:55
we therefore divide the frontal bone into three parts. A squamous part,
5:59
a nasal part and two paired orbital parts. Let’s highlight some structures on the frontal
6:04
bone. The frontal bone has something called the Frontal Eminence. These are the two prominent,
6:10
round, areas on the external surface of the squamous part of frontal bone. They are areas
6:15
of the frontal bone where its convexity is at its maximum, and they also contain the ossification
6:24
centers, so the first area of a bone to start ossifying. Alright, on the sides we can see
6:29
the temporal lines. The temporal lines are two curved elevations on the frontal bone’s outer
6:33
surface. They extend from the zygomatic process, curve toward the parietal bone, and split into
6:40
superior and inferior parts, which continue as the parietal temporal lines we saw earlier, providing
6:46
attachment for the temporal fascia and marking the upper front boundary of the temporal fossa,
6:51
The temporal fossa is one of the largest landmarks of the skull,
6:55
it’s a shallow depression that is formed by four skull bones, the parietal, temporal, frontal and
7:01
sphenoid bones. Kinda makes sense once we rush through the bones of the neurocranium, but it’s
7:05
mainly occupied by the temporalis muscle which has a wide attachment spread across the fossa. And it
7:11
also has some important neurovascular structures such as the deep temporal vessels and nerves.
7:17
Then we got the superciliary arch which are paired arches located above the orbit. Between
7:23
them is the glabella, which is a flattened area above the nasal root. And then all the
7:28
way on the lateral surface is the zygomatic process, which connects to the zygomatic bone.
7:33
Now, focus on the supraorbital margin for a moment, we can see the supraorbital notch,
7:39
which is a notch or foramen above the orbit that contains the supra-orbital vessels and the lateral
7:44
branch of the supra-orbital nerve. Medial to the supraorbital notch is the Frontal notch,
7:50
which is a small ridge, or sometimes a hole or foramen, which transmits
7:55
the medial branch of the supra-orbital nerve. Let’s take a look at the inner surface of the
8:00
squamous part now, we can see a ridge on the midline of the frontal bone. The upper one is
8:05
called the groove for the superior sagittal sinus, containing the superior sagittal sinus, which
8:11
again is one of the dural venous sinuses in our brain. And below it is the frontal crest, which
8:16
is the site of attachment of the falx cerebri. Within the orbit, we can see the fossa for the
8:22
lacrimal gland, which contains the lacrimal gland responsible for the production of tears. We can
8:27
see the nasal spine of the frontal bone. The nasal spine helps form the bony nasal septum and the
8:33
frontoethmoidal suture. On the medial surface of the orbit, we can see the trochlear fovea,
8:40
which are small depressions where the trochlea of the superior oblique muscle attaches. In some
8:45
people, instead of a shallow depression, a small bony projection called the trochlear
8:50
spine is present in the same location. Then if we look at the bottom surface of the frontal bone,
8:55
we can see the anterior ethmoidal groove, which is a small depression on the medial
8:59
orbital part of the frontal bone that forms the anterior ethmoidal foramen with the ethmoid bone,
9:06
allowing passage of the anterior ethmoidal nerve and vessels. And behind it, similarly
9:11
is the posterior ethmoidal groove, which is also a depression that forms the posterior ethmoidal
9:16
foramen with the ethmoid bone, transmitting the posterior ethmoidal nerve and vessels.
9:21
Ok, now the frontal bone is quite interesting. Look at the skull from an anterior perspective.
9:27
Cut it in half, look at it from this side, and we can see a hole within the frontal bone,
9:32
and this is famously known as the frontal sinus. The frontal sinus is the most superior of the four
9:39
paranasal sinuses we have, and it develops after the first year of life, reaching full
9:44
size by adulthood. So when you breathe in, air enters the frontal sinus, where it gets warmed
9:50
and humidified. This happens because the sinus is lined with respiratory mucosa that helps
9:56
condition the air before it reaches your lungs. The frontal sinus also makes the skull lighter
10:02
and may help resonate your voice, make it sound clearer. It drains into the middle nasal meatus
10:07
through a small passage called the frontonasal duct, and it has a thin septum separating the
10:13
frontal sinus into a left and right side. In some cases, the frontal sinus can become
10:18
inflamed due to infections, leading to frontal sinusitis, which may cause headaches, facial pain,
10:23
and pressure above the eyes. Usually because the draining pathway is clogged.
10:28
Alright. So that is the frontal bone. Let’s do the occipital bone.
Occipital Bone
10:33
The occipital bone is an unpaired bone which covers the back of the head. It makes
10:38
up a large portion of the basilar part of the neurocranium and entirely houses the cerebellum.
10:44
The occipital bone is composed of four main parts, there’s the squamous part, the basilar
10:50
part and the two lateral parts. And a large hole in the middle known as the foramen magnum,
10:56
which contains the medulla oblongata as it changes into the spinal cord. And it also contains the
11:01
vertebral arteries, the anterior spinal artery, the paired posterior spinal arteries, the spinal
11:07
root of the accessory nerve and the spinal vein. Let’s look at the occipital bone from the inside
11:12
as well, and then take a mental picture of this. Let’s now isolate the occipital bone. So here we
11:19
see the three parts, and the foramen magnum. And now, let’s highlight the most important
11:25
landmarks on this bone, and focus on the external surface first. Here we can see the external
11:31
occipital protuberance, which is a palpable tubercle on the posterior surface of the skull,
11:36
it is typically more palpable in males, and serves as an attachment point for the nuchal ligament
11:41
and the trapezius muscle. Extending inferiorly is the external occipital crest, which is a vertical
11:48
crest for attachment of the nuchal ligament. Then we got the Highest nuchal line
11:56
for the attachment of the nuchal fascia, The superior nuchal line,
11:59
serving as the attachment of the trapezius and sternocleidomastoid, and the Inferior nuchal line,
12:00
serving as the attachment of the rectus capitis posterior major and minor. Next we have the
12:05
condylar fossae, which are two depressions on the underside of the occipital bone. They
12:10
accommodate the atlas’s superior articular facets during head extension, and in some individuals,
12:16
a condylar canal can be seen in its floor. When this canal is present, it allows for the passage
12:21
of an emissary vein, which connects the sigmoid sinus inside the skull to veins in the neck.
12:27
Then we can see the occipital condyles, which are two oval projections on the underside of
12:32
the occipital bone, that provide attachment for the alar ligaments and form the atlantooccipital
12:38
joints by articulating with the atlas, allowing head movement. Then we got the
12:42
pharyngeal tubercle, which is a small midline bump on the underside of the basilar part of
12:48
the occipital bone. It serves as the attachment point for the pharyngeal raphe, which supports
12:53
the muscles of the pharynx during swallowing. Now, to make it easier to navigate, we typically
12:59
landmark the external surface of the occipital bone by dividing it into two main areas:
13:05
the occipital plane and the nuchal plane. The occipital plane is the smooth, upper part,
13:10
providing attachment for the epicranial aponeurosis. In contrast, the nuchal
13:15
plane is the rough, lower part, where many neck muscles insert and the nuchal ligament attaches,
13:20
helping with head movements. For the borders we can see the Lambdoid border which forms the
13:25
lambdoid suture with the parietal bone, we can see the Mastoid border, which connects to the
13:30
temporal bone to form the occipitomastoid suture. And we can see the spheno-occipital synchondrosis,
13:35
which is a cartilaginous connection between the sphenoid and occipital bone. Alright,
13:41
let’s now quickly do the inner surface. On the inner surface of the basilar part
13:45
we can see the clivus, which is a slope on the internal surface located beneath the brain stem,
13:51
containing the basilar artery and basilar venous plexus. Then we got the groove for the inferior
13:57
petrosal sinus. There’s the jugular notch, which forms the jugular foramen, together with the
14:02
jugular notch of the temporal bone. And sometimes we can see the Intrajugular process, which is
14:08
located inside the jugular notch and separates the jugular foramen into two compartments.
14:13
What else can we see here. We can see the groove for the sigmoid sinus, which contains the sigmoid
14:18
sinus. We can see the internal occipital protuberance, which contains the confluence
14:24
of sinuses, which is the connection point of the transverse, straight, superior sagittal
14:29
and occipital sinuses. We can see the cruciform eminence, which is a cross-shaped prominence
14:35
formed by the grooves for the occipital, superior sagittal and transverse sinuses,
14:40
and it divides the occipital bone into two cerebral fossae and two cerebellar fossae.
14:45
We can see the groove for the transverse sinus, which contains the transverse sinus as well as
14:50
the attachment of the tentorium cerebelli, the groove for superior sagittal sinus,
14:55
which contains the superior sagittal sinus and the attachment of the falx cerebri,
15:00
and the groove for occipital sinus, which contains the occipital sinus and the attachment of the falx
15:06
cerebelli. And here you see how those dural venous sinuses occupy each groove. So those
Bones of the Cranial Base
15:12
are all the bones I wanted to talk about in this segment, those are all the bones of the
15:17
skull cap. Next let’s quickly run through the bones of the cranial base, which are
15:21
the temporal bone, sphenoid, and the ethmoid bone. Now let’s take this skull, and look at the inside,
15:28
and gray out the bones we talked about earlier, so we now have the temporal bone,
15:32
sphenoid bone and the ethmoidal bone. Let’s now start with the temporal
Temporal Bone
15:36
bone. The temporal bone is a paired bone that consists of three main parts. The squamous part,
15:42
the petrous part, and the tympanic part, which is the area underneath here where your
15:46
ear canal opens up at. Now, orientation is the key in understanding this bone.
15:52
Keeping the same view, let’s isolate the lateral bone, and the superior view of this bone. So
15:58
here again we see the three parts it’s made out of. And now, let’s highlight the most important
16:03
landmarks of this bone. Because it has so many functions. If we start with the squamous part,
16:09
the most noticeable structure is the Zygomatic process, The zygomatic process is a long,
16:15
thin projection of the temporal bone that extends forward to form the posterior part
16:20
of the zygomatic arch, connecting with the zygomatic bone at the temporozygomatic suture.
16:25
It has an articular tubercle, which provides attachment for the temporal fascia,
16:29
masseter muscle, and lateral ligament of the temporomandibular joint. We can see
16:34
the Supramastoid crest, which is the dorsal continuation of the zygomatic process. And we
16:40
can see the mandibular fossa, which is the articular fossa for the temporomandibular
16:45
joint, allowing free jaw movement. Alright, now let’s do the tympanic part.
16:50
The tympanic part is located here, this whole part here. Now you’ve probably
16:56
seen this picture somewhere. This is an image illustrating how the external ear,
17:01
middle ear, and internal ear look like. All of your ear components are located
17:06
within the tympanic part of the temporal bone. Now let’s expand on this. We can see
17:12
the eustachian tube here as well leading to the pharynx. The entrance into the external ear is
17:18
called the external acoustic opening, which leads way into the external acoustic meatus,
17:23
or the ear canal. Which goes all the way to the tympanic membrane. The tympanic
17:28
membrane is a thin, cone-shaped structure that separates the external ear from the
17:33
middle ear, vibrating in response to sound waves. Surrounding the tympanic membrane is the tympanic
17:39
ring, a bony ridge within the tympanic part of the temporal bone. It provides structural support
17:46
for the membrane and helps anchor it in place. So, the external acoustic opening is here. Now,
17:53
looking at the external acoustic opening from the temporal bone, we can see the petrotympanic
17:59
fissure just anterior to it. This narrow slit connects the tympanic cavity to the
18:05
infratemporal fossa and allows passage for the chorda tympani nerve and anterior tympanic artery.
18:12
Ok, so, we covered the squamous part, we covered the temporal part,
18:17
and then we have the petrous part, so let’s go ahead and cover that one. The petrous part of
18:21
the temporal bone has an anterior surface, and a posterior surface. There is a superior border,
18:28
which attaches to the tentorium cerebelli, and contains the groove for the superior petrosal
18:34
sinus. Then the pointy end there is called the Apex of the petrous part. Posteriorly
18:40
we got the posterior border, which connects to the occipital bone. And then, if we look
18:45
at an inferior view, we will find the inferior surface containing some structures as well. So,
18:52
let’s go ahead and cover all the structures here. On the anterior surface we can see the tegmen
18:57
tympani. The tegmen tympani is considered a weakened part of the skull because it is a
19:03
thin bony plate that separates the middle ear from the middle cranial fossa. Since it’s very thin,
19:10
it is prone to fractures or erosion, especially in cases of chronic ear infections or increased
19:15
intracranial pressure. If compromised, infections can spread from the middle ear to the brain,
19:20
leading to serious conditions like meningitis or brain abscesses.
19:24
Alright next is the arcuate eminence, which is a bulge formed by the anterior semicircular canals.
19:31
There’s the groove for the superior petrosal sinus, then we got the groove for the lesser
19:32
petrosal nerve which transmits the lesser petrosal nerve, groove for the greater petrosal nerve,
19:38
and the trigeminal impression, which is a shallow fossa for the trigeminal ganglion.
19:43
If we change the angle here we can see the groove for the inferior petrosal sinus, there are many
19:49
grooves on these bones for the dural venous sinuses. We can see the subarcuate fossa,
19:54
which is a small depression on the posterior surface, we can see the jugular notch,
19:59
which remember forms the jugular foramen together with the occipital bone. Other
20:03
things we can see is the mastoid process. The mastoid process is a large bony projection that
20:10
contains mastoid air cells, which help regulate ear pressure, and serves as an attachment site
20:15
for muscles like the sternocleidomastoid, splenius capitis and longissimus capitis
20:20
Next to it is the mastoid notch, serving as the origin for the posterior belly of digasticus.
20:27
We have the groove for the occipital artery. And then we can see the styloid process,
20:31
which is a thin pointed projection that serves as an attachment site for the stylopharyngeus,
20:36
styloglossus, and stylohyoid muscles, along with the stylomandibular and stylohyoid ligaments.
20:43
Right next to it is the stylomastoid foramen, which is the external opening of the facial canal.
20:50
Lastly, we can see the groove for the sigmoid sinus. Now. You see the internal acoustic opening
20:56
here? It makes way for the facial nerve to exit the skull, through the stylomastoid foramen. This
21:02
canal is called the facial canal, and we divide it into the labyrinth part, geniculum, tympanic part,
21:08
and the mastoid part, depending on which region it lies in. Alright, that was the temporal
21:13
bone. I told you this is going to be a very detailed video, Imma make you an expert in this.
Sphenoid Bone
21:19
Next, the sphenoid bone, is a beautiful bone. This is a butterfly-shaped bone located at
21:25
the base of the skull, forming part of the cranium, orbit, and nasal cavity. In a way,
21:30
it’s literally the centre of our skull, connecting the neurocranium with the viscerocranium.
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The sphenoid bone consists of an unpaired body and three paired projections, the greater wing,
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lesser wing and pterygoid processes. Now, the sphenoid bone has holes leading structures
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through it. One of which is the superior orbital fissure, leading certain cranial
21:51
nerves from the brain to the orbit. We have the optic canal leading the
21:55
Ophthalmic artery, Ophthalmic plexus and the Optic nerve to the eye.
21:59
We got the foramen rotundum, which contains the maxillary nerve. We got the foramen ovale,
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for the mandibular nerve, then if we tilt it a little bit we can see the foramen spinosum, which
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contains the middle meningeal artery and vein and the meningeal branch of the mandibular nerve. Then
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if we look at the anterior skull, there’s the superior orbital fissure, and then down here,
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between the greater wing and the maxilla is the inferior orbital fissure, which contain things
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liek the zygomatic nerve, infraorbital nerve and artery and the inferior ophthalmic vein.
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Now, let’s run through the landmarks on this bone. Here is a very very imporatant structure called
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the sella turcica. Which is latin for the ‘Turkish saddle’. It consists of the Hypophysial fossa,
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that contain the hypofysis. Posterior wall is called the Dorsum sellae, that has the Posterior
22:49
clinoid processes on either side, which function as the attachment of the sellar diaphragm and the
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tentorium cerebelli. In the front we have the tuberculum sellae, then we have the chiasmatic
23:00
sulcus or the Prechiasmatic sulcus it’s also called, which is a shallow groove located anterior
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to the optic chiasma. Then we got the anterior clinoid process which provides another attachment
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point of the tentorium cerebelli. And posteriorly we see the clivus, and on the sides, the carotid
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sulcus for the internal carotid artery. Let’s now turn it to the front, we can see the sphenoidal
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crest, and the sphenoidal rostrum. Then we got the sphenoidal concha, each located lateral to the
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sphenoidal crest and contributes to the formation of the anterior wall of a sphenoidal sinus. For
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the pterygoid processes we got the medial plate for the attachment of the superior constrictors
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of the pharynx, and the lateral plate, which serves as an origin of the inferior head of
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the lateral pterygoid muscle. At the bottom of the medial plate we have the pterygoid hamulus, which
23:52
serves as a pulley for the tensor veli palatini tendon during swallowing. Posteriorly we can see
23:58
the Pterygoid fossa, which serves as the origin for the medial pterygoid muscle, and the scaphoid
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fossa, origin for the tensor veli palatini. Alright, finally, let’s run through the last
Ethmoidal Bone
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bone, the ethmoidal bone. The ethmoidal bone is quite interesting, it serves as the medial wall
24:16
of the orbits and also forms parts of the nasal cavities. And if we now, remove the skull bones,
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you’ll see that it looks like this. It has three major parts. We have the cribriform
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plate at the top, perpendicular plate, and then the ethmoidal labyrinths at either side. So,
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let’s look at it from an anterior perspective and a superior perspective.
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At the top we can see the cribriform foramina, small holes that transmit the olfactory nerves,
24:43
there’s the crista galli, which is a bony plate that form part of the attachment of the
24:48
falx cerebri. Facing the orbits are are orbital plates, we can see the posterior ethmoidal cells,
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which open into the posterior nasal meatuses. Within the ethmoidal bone, we can find air
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bubbly bony rooms called ethoidal cells, and they’re generally divided into the anterior,
25:07
middle and posterior ethmoidal cells. So anterior and middle air cells open into the middle nasal
25:14
meatus, and posterior eithmoidal cells open into the superior nasal meatus. Then we got the
25:21
nasal conchae, which divide the nasal cavity into nasal meati. So we have the superior nasal concha
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hidden in there, middle nasal concha, which has an arched projection called the uncincate process.
25:35
There we go, finally done with all the detailed anatomy of all the bones of the neurocranium.
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Lastly, just very quickly, I wanna run you through the main foramina of the skull,
Foramina of the Skull
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so you have them all in one place. We first have the foramen magnum for the brainstem and spinal
25:51
cord. In there we have the hypoglossal canal, for mainly the Hypoglossal nerve. We got the
25:56
jugular foramen, which contain things like the Internal jugular vein, Glossopharyngeal nerve,
26:01
Vagus nerve, Accessory nerve and Posterior meningeal artery. We got the internal acoustic
26:07
meatus which contain the facial nerve (CN VII), vestibulocochlear nerve (CN VIII),
26:14
labyrinthine artery and veins, vestibular ganglion. We got the foramen Lacerum for
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things like the internal carotid artery, Internal carotid plexus, Internal carotid venous plexus,
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Deep petrosal nerve, Greater petrosal nerve, Lesser petrosal nerve and the Recurrent branch
26:31
of the foramen lacerum. We got the foramen spinosum which contains the middle meningeal
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artery and vein and the meningeal branch of the mandibular nerve. Foramen ovale,
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for the mandibular nerve, adn foramen rotundum, which contains the maxillary nerve.
26:46
Alright, we finally managed to go through the detailed anatomy of all the bones of
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the neurocranium. In the next video we’ll go through the bones of the viscerocranium,
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all the bones you see here on the right. If you want a handmade PDF version of
26:59
this lecture or an organized list of all my videos, you can find everything on my website.
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Thank you so much for watching another one of my videos! If you enjoyed it or learned
27:07
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