Bones of the orbit
Summary
TLDRThis educational video script delves into the anatomy of the bony orbit, discussing the bones that comprise it, including the frontal, maxilla, zygomatic, sphenoid, ethmoid, and lacrimal bones. It highlights the concept of blowout fractures, common injuries in the orbit caused by increased pressure from impacts, most frequently affecting the floor of the orbit. The script also touches on the importance of CT radiography in diagnosing these fractures, providing a detailed yet accessible explanation suitable for students and enthusiasts of anatomy.
Takeaways
- 😀 The video discusses the bones that make up the orbit, following a previous session on paranasal sinuses.
- 🦴 The bones of the skull, specifically the orbit, are examined in detail, including the bones' roles and connections.
- 👁️ Blow fractures are highlighted as an interesting type of fracture that can occur in the orbit due to a forceful impact.
- 🔍 The script explains how thin some bones are around the orbit, which can lead to fractures, particularly in the maxillary and ethmoid bones.
- 🧱 The individual bones forming the orbit are identified, including the frontal bone, maxilla, zygoma, sphenoid bone, nasal bones, lacrimal bone, and ethmoid bone.
- 🌈 The script uses color coding on a skull model to differentiate and explain the function of each bone in the orbit.
- 🚫 The zygomatic arch is clarified as a complex structure composed of multiple bones, not just the zygomatic bone.
- 👃 The ethmoid bone's role in the nasal cavity and its connection to the olfactory system via the cribriform plate is discussed.
- 💧 The lacrimal bone's association with tear production and drainage through the nasolacrimal duct is explained.
- 🧊 The video emphasizes the packed nature of the orbit with muscles, nerves, blood vessels, and fat, which can affect the outcome of a blow to the eye.
- 🔬 CT radiography is mentioned as the preferred method for assessing blowout fractures over traditional X-rays due to its enhanced detail.
Q & A
What are the paranasal sinuses?
-The paranasal sinuses are air-filled cavities within the bones of the skull that are connected to the nasal passages. They include the maxillary, frontal, sphenoid, and ethmoid sinuses.
What is a blowout fracture?
-A blowout fracture is a type of fracture that occurs in the bones surrounding the eye, typically caused by a forceful impact such as a sporting accident. It can cause the thin bone to fracture into the adjacent sinuses.
Which bones are involved in the formation of the orbit?
-The bones involved in the formation of the orbit include the frontal bone, maxilla, zygomatic bone, sphenoid bone, ethmoid bone, lacrimal bone, and palatine bone.
Why are the bones around the orbit prone to fractures?
-The bones around the orbit are prone to fractures due to their thinness and the pressure increase within the orbit caused by a blow, which can lead to the weakest part of the bone, such as the thin bone of the maxilla, fracturing into the maxillary sinus.
What is the function of the infraorbital foramen?
-The infraorbital foramen is a canal through which the infraorbital nerve, artery, and vein pass, providing sensory information and blood supply to the face.
What is the significance of the optic canal?
-The optic canal is a tubular canal that houses the optic nerve (cranial nerve II) and the ophthalmic artery, which supplies blood to the retina of the eye.
What is the role of the superior orbital fissure?
-The superior orbital fissure connects the middle cranial fossa with the bony orbit, allowing cranial nerves that innervate the extraocular muscles to enter the orbit.
What is the purpose of the periorbital fat mentioned in the script?
-The periorbital fat serves to fill the space within the bony orbit, providing cushioning and support to the eye and surrounding structures.
How can a blowout fracture be assessed?
-A blowout fracture is commonly assessed using CT radiography, which provides more detailed information than an X-ray and is the preferred method for diagnosis.
What is the nasolacrimal duct and its function?
-The nasolacrimal duct is a passageway that drains tears from the lacrimal sac into the nasal cavity, allowing tears to be cleared from the eye.
Why might a blow to the eye cause the eye to appear sunken?
-A blow to the eye can cause a blowout fracture, which may result in the eye being pulled back slightly into the orbit due to the increase in pressure within the orbit and subsequent bone displacement.
Outlines
🦴 Anatomy of the Orbital Bones and Blowout Fractures
This paragraph delves into the intricate structure of the bones that make up the orbit, including the frontal bone, maxilla, zygoma, sphenoid, nasal, lacrimal, ethmoid, and palatine bones. It discusses the concept of blowout fractures, which are fractures that occur due to a forceful impact to the orbit, often resulting from sporting accidents. The speaker explains how the bones in the orbit are not as thick as one might expect, especially the maxillary sinus and ethmoid air cells, making them susceptible to such fractures. The video also mentions the use of a pipe cleaner to demonstrate the pathways through the fissures and foramina of the skull.
👁️🗨️ The Ethmoid Bone and its Role in the Orbit
The focus of this paragraph is on the ethmoid bone, which forms the medial wall of the orbit and contributes to the superior part of the nasal cavity. It highlights the cribriform plate, a part of the ethmoid bone, which is crucial for the passage of the olfactory nerve responsible for the sense of smell. The speaker also describes the presence of the lacrimal bone, its relation to tear production, and the path of tears through the nasolacrimal duct into the nasal cavity. Additionally, the paragraph touches on the extraocular muscles, nerves, blood vessels, and fat within the orbit, emphasizing the packed nature of this space.
👁️🗨️ Fissures and Foramina of the Orbital Bones
This section of the script explores the various fissures and foramina present in the orbital bones, which are essential for the passage of nerves, arteries, and veins. The optic canal, superior orbital fissure, and inferior orbital fissure are specifically mentioned, with the speaker explaining their functions and the structures that pass through them. The optic canal houses the optic nerve and artery, while the superior and inferior orbital fissures allow for the passage of cranial nerves and blood vessels that serve the orbit and facial regions. The speaker also demonstrates the pathway of the nasolacrimal duct using a pipe cleaner, emphasizing the quality of the model used for demonstration.
🔍 Diagnosis and Types of Blowout Fractures
The final paragraph discusses the diagnosis of blowout fractures, emphasizing the use of CT radiography over traditional x-rays for better clarity and detail. It explains how a blow to the eye can lead to an increase in pressure within the orbit, causing the thinnest bone to fracture, most commonly the floor of the orbit formed by the maxilla. The speaker describes the potential for the eye to appear sunken due to the fracture and the possibility of different types of blowout fractures affecting various walls of the orbit. The paragraph concludes with a summary of the key points regarding the bones of the orbit, the sinuses, and the nature of blowout fractures.
Mindmap
Keywords
💡Orbit
💡Paranasal Sinuses
💡Blowout Fracture
💡Maxilla
💡Zygomatic Bone
💡Ethmoid Bone
💡Sphenoid Bone
💡Palatine Bone
💡Lacrimal Bone
💡Fissures and Foramina
💡CT Radiography
Highlights
Review of bones comprising the orbit and paranasal sinuses from the previous week's discussion.
Introduction to blow fractures, an interesting type of fracture occurring in the orbit due to a blow.
Explanation of how the bones around the orbit are thin and can lead to blowout fractures.
Discussion on the bones involved in the formation of the orbit, including the frontal, maxilla, zygoma, sphenoid, nasal, lacrimal, and ethmoid bones.
Clarification that the zygomatic arch is a complex of bones, not a single bone.
Description of the maxilla's role in forming much of the floor of the orbit.
Identification of the ethmoid bone's complex structure and its contribution to the medial wall of the orbit and the nasal cavity.
Explanation of the cribriform plate's role in housing the olfactory bulbs and its connection to the sense of smell.
Highlighting the sphenoid bone's presence in the back of the orbit and its importance.
Mention of the lacrimal bone's role in tear drainage through the nasolacrimal duct.
Overview of the bones forming the bony orbit and their functions.
Discussion on the extraocular muscles, nerves, blood vessels, and fat within the orbit.
Identification of the foramina and fissures around the orbit, such as the supraorbital and infraorbital foramina and the superior and inferior orbital fissures.
Explanation of the trigeminal nerve branches passing through the foramina and their sensory roles.
Description of the optic canal's function in housing the optic nerve and artery.
Discussion on the assessment of blowout fractures using CT radiography as opposed to X-rays.
Conclusion summarizing the bones of the orbit, their functions, and the concept of blowout fractures.
Transcripts
[Music]
[Applause]
so I thought we'd have a look at the
bones comprising the orbit we were
talking about the paranasal sinuses last
week and there are the videos about the
bones of the skull and the parameter of
the skull and that sort of thing but
always well worth looking at the all
pretty itself in a little bit of detail
we can talk about blowing fractures so
interesting type of fracture that occurs
here with a blow to the orbit usually
caused by some saw you know a sporting
accident like a ball or back to the to
the orbit which doesn't fracture in the
way that you might expect if you watch
the paranasal sinuses video and we
looked to see how thin some of the bones
are around this area then maybe you
would expect these strange blowout
fractures to fracture other bones than
the bones at the front and look at those
so we'll look at each bone in turn will
poke a pipe cleaner through the fissures
and foramina and see where they go and
talk about blowout fractures all right
so on our plastic scale here if we look
carefully we can see the individual
bones here's the frontal bone this is
the maxilla here and then we have the
zygoma out here so they're forming part
of their zygomatic arch with the
zygomatic bone here we've got the
sphenoid bone back in there we've got
the nasal bones here the lacrimal bone
and the ether mode bone and you can
maybe see a palatine bone on the back
there see all that no of course you
don't because it's all white if we have
a look at our colorful skull then we can
see a little bit more I mean as I've
said before why are these bones the same
color so close to each other so watch
out for that but this big mustard bone
here is the frontal bone the nice
purpley bone here is the maxilla
interestingly we start off with left and
right and mags ILI's are two separate
bones and then this this fissure that
you see here in you
this is probably this is more than
likely this is fused right if you only
ever talk about a single maxilla the the
two halves because we're segmented
animals and we form into halves and
stuff the two halves meet and fuse here
giving us a single maxilla anyway you
can see how the maxilla is forming much
of the floor of the orbit if this bony
cavity here is the orbit there's the
maxilla and that the frontal bone is
forming much of the roof laterally then
this is also yellow the brighter yellow
right now this is the zygomatic bone or
the zygoma and a zygomatic arch is
actually a complex of bone so here we've
got the temporal bone right and this is
contributing to the zygomatic arch and
this is the maxilla this is also
contributing to the Maya zygomatic
complex but there's a coma and the site
this is also known as the zygomatic bone
this is a separate thing
so there's a grammatic arch is complex
of bones the zygomatic bone is a bone
make sense good
so the zygomatic bone is forming part of
the lateral wall of the orbit and then
if we're talking about yellow bones if
we look inside if we look in there at
the medial wall of the orbit you can see
another yellow bone and that's the
ethmoid bone then Eve moy bone is a
really difficult bone to figure out
conceptually where it is in your head
it's difficult to work out in your head
where it is in your head but it's it's
it's it's it's it's it's it's um so it's
the ethmoid bone is a cuboidal color if
you think of a rectangular cuboid shaped
bone forming the medial wall of the
orbit and also contributing to the
superior part of the nasal cavity as you
can see in there and also
the ethmoid bone is also here so this is
the frontal bone now this is the the
anterior fossa within the cranial cavity
and this holy space here we call the
cribriform plate that's where we find
the olfactory bulbs that the bulbs of
cranial nerve one the nerve responsible
for all the fashion smell detection
sending through nerve fibers through
those little holes to get into the nasal
cavity does that help so that's the
ethmoid bone right see my bone is there
let's on nasal cavity right middle II me
you might need to spend some time
looking at that one and then we have the
back again right so at the back here
within the orbit we've got the sphenoid
bone in red sphenoid bone we can also
see laterally here in red and if we look
in the back of you orbit there's the
sphenoid bone in red now there's another
bone there also in your head which is
see this here this is the hard palate
you can see the purple of the magaziner
they're kind of just about I turn it
over get some light on it it's very dark
so the purple of the maxilla and then
you've got the red of the palatine bones
and those palatine bones also extend up
into the orbit just posterior Magaziner
so we've got the red palatine bone next
to the red sphenoid bone there are more
colors in the rainbow
that could have been used and then have
you noticed there's one more bone we
haven't talked about if the orange bone
here this is the lacrimal bone so the
lacrimal bone lacrimation these tears is
forming tears so the lacrimal gland is
up here and then tears wipe across they
run across your eye to drain here so
down here we've got the nasolacrimal
duct and there's a little lacrimal sac
as well here collecting those two
and the tears drain through the
nasolacrimal duct into the nasal cavity
it actually opens in the inferior meatus
right in there anyway so those are the
bones of the orbit harder to see on the
white skeleton but we've got maxilla
lacrimal bone this boy bone frontal bone
up here like a massive bone sphenoid
bone in the back and then if you really
clever the tip of the Palatine bone so
those bones are forming the bony orbit
and inside that bony orbit then we've
got the eye obviously but we've also got
all of these extra ocular muscles extra
ocular meaning they these the muscles
outside of the eye that are moving the
eye around then we have nerves of blood
vessels and that sort of thing but the
other thing that's in here is a whole
load of fat periorbital faster than a
load of fat here packing this space it's
all nicely filling the orbit here
feeling that bony orbit space there's
not a lot of space we see here oh look
there's that lacrimal sac there that I
was talking about
there's the lacrimal duct and getting
the nasal cavity in there so then on the
skull we can see some parameter right
some extra bits and bobs so see this
hole here and then we've got what on
this skull is a hole oh look and
sometimes it's just a notch so you can
see why sometimes there isn't that
little bit about there it's just a notch
so this is the supraorbital notch or in
this case maybe supraorbital foramen and
this would be the infraorbital foramen
now look see where that pipe cleaner
comes out now you see so this is the
infraorbital foramen it's a bit of a
canal and again this starts off as a
groove and it gets covered over by the
bone so through here
passes the infraorbital nerve and artery
and vein and through here passes the
supraorbital nerve artery and vein going
up here so these are branches of the
trigeminal nerve which are going to give
you carrying sensory information from up
here and down here right mmm we should
remember this nerve you should love how
we yeah we should certainly remember
this nerve later and then we can also
see a perennial favorite but this is
always nice
this is the optic canal so that that's
passing through there so that's the
optic canal it's a nice round tubular
canal guess what goes through there the
optic nerve cranial nerve - and the
artery within it supplying blood to the
retina but we can see next to it we can
see these fissures currently so there is
the optic canal and then next to it
we've got this fissure haven't we
so this is the the fissure then that's
the superior orbital fissure and that
look that's connecting the middle
cranial fossa with the bony orbit so
this this is the way in which the the
cranial nerves innervating the muscles
of the orbit the extraocular muscles
that's how they get in there so
basically that's how everything gets
from the cranial cavity to the orbit
that doesn't go through the optic canal
everything else goes through the
superior orbital fissure and if there's
a superior orbital fissure and there
must be an inferior orbital fissure and
that it can you see that if that's the
superior orbital fissure then let's see
that one down there that that is the
inferior orbital fissure then these is
another fissure but it's in the inferior
part of the orbit now if we stick a pipe
cleaner through there where does that go
that's appearing in the deep face in
there so the the inferior orbital
fissure is linking the orbit with the
deep face and we see veins draining
through there from the orbit into the
facial vein
somebody drilling over there and
somebody lobbing stuff in a skip over
there
it's a big hole he's drilling still
throwing things in this Kip okay so the
aim today is not to talk about
everything in the orbit and all the
nerves and the arteries and the veins
and everything like that
the aim today is to talk about the bones
of the orbit so we've talked about the
bones of the orbits and the fishes and
the major parameter I think I missed
boom oh yeah
okay what was it like so how good is
this skull do you think if I pass me
pipe-cleaner
dying through that nasolacrimal duct
reckon it's just going to end because
it's plastic or did you reckon it's
actually model this is going to come out
through the inferior nasal mucus how
would you reckon would you reckon it
doesn't go anywhere all right how about
this one oh that one goes through let's
try an orange pipe cleaner yeah oh you
can see that in there that's what I mean
about the nasolacrimal duct opening in
that underneath that inferior nasal
Nieto's in there right in there there
you go so that's a high-quality skill
the nasolacrimal duct er there
otherwise that's it that's the bones of
the skull now what happened with a blow
to the face and there are a number of
interesting things that happen to the
bones of the face in a number of
different practice like different types
of LeFort fracture the balance if we
talk about blowout fractures now a blow
to the eye neither the bone around here
is actually pretty tough and of course
we've got as I said this stuff inside
the orbit is is all packed together with
all the interesting things like the
muscles and the nerves and the blood
vessels and the eye itself and all that
but we've also got a little of fat in
there so this is a really really packed
space which means that a blow
so the orbit here to the I can increase
the pressure within the orbit and that
means that when we were looking at the
paranasal sinuses we saw that that
maxillary sinus is in here and it fills
most of the maxilla so the bone here
becomes very very thin and we saw the
ethmoidal air cells medially which means
that the bone there is also very very
thin and then we see the frontal sinuses
up here which means there is a thinness
up here as well so these bones are not
as thick and tough as you think they are
so a blow to the eye increases the
pressure within the orbit and then the
thing that's going to be fair gonna fail
is the thing that's gonna be weakest so
I think most commonly that you get a
fracture in the inferior wall so in the
floor of the orbit so that's your
blowout fracture the the impact happens
the pressure inside the orbit increases
and the thin bone of the maxilla down
here fractures into the maxillary sinus
now you're looking at in patients had
this you're looking at your patient
who's had this blow and it might not be
immediately obvious that a blowout
fracture has occurred because the bones
around here are likely to remain intact
there's gonna be a loss wedding a lot of
bleeding in the eyes gonna be looking a
bit weird anyway but what you might see
is that the eye might be pulled back a
little bit into the orbit so maybe a
little bit sunken or it might take a day
or two to notice that as the swelling
goes down so that's a blowout fracture
one example of a blowout fracture
obviously if we're considering all of
the surfaces of the the bony orbit then
you could get a blowout fracture in the
roof in the floor in the lateral wall or
in the medial wall so a superior blowout
fracture my occurrence the frontal sinus
that's less common now the lateral wall
is actually very very thick we've got as
I go the zygomatic bone here so the
lateral wall is less likely to to get a
blowout fracture because it's thicker
than the others so immediately a
fracture will blow out into the ether
mode bone in here into those ethmoidal
air cells so mean so that a blowout
fracture to the floor I think is most
common and then
easily is somewhat common and then a
blowout fracture and laterally or to the
Rufus is much less common and nowadays
to the preferred method of assessing a
blowout fractures with is with CT
radiography it tells you a lot more than
an x-ray I don't think people really use
x-rays so much anymore so there you go
the bones of the bony orbit and hark
back to the sinuses and what a blowout
fracture is how it's caused and where
you should look alright hopefully that's
a nice short one this week possibly not
though all right see you next week
[Music]
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