Bones of the orbit

Summary

This 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

00:00

🦴 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.

05:03

👁️‍🗨️ 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.

10:07

👁️‍🗨️ 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.

15:10

🔍 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.

Keywords

💡Orbit

The orbit refers to the bony socket in the skull that houses the eye and its associated structures. In the video, the orbit is the central theme, with a focus on the bones that comprise it and the potential for fractures, particularly 'blowout fractures,' which occur due to increased pressure within the orbit from a blow to the eye.

💡Paranasal Sinuses

Paranasal sinuses are air-filled cavities within the bones of the face and skull. The video script mentions these sinuses in relation to the bones around the orbit, particularly the thinness of the bones in these areas, which can contribute to the occurrence of fractures.

💡Blowout Fracture

A blowout fracture is a specific type of fracture that occurs in the bones surrounding the eye, often as a result of a forceful impact. The script explains that such fractures commonly affect the floor of the orbit, causing the eye to appear sunken due to the displacement of the bone into the maxillary sinus.

💡Maxilla

The maxilla is one of the bones forming the orbit, contributing significantly to the floor of the eye socket. The script describes how the maxilla is susceptible to blowout fractures due to the thinness of the bone in the area of the sinuses.

💡Zygomatic Bone

The zygomatic bone, also known as the cheek bone, forms part of the lateral wall of the orbit. The script mentions the zygomatic bone as part of the zygomatic complex, which includes the zygomatic arch and contributes to the structure of the face.

💡Ethmoid Bone

The ethmoid bone is a complex bone that forms the medial wall of the orbit and is part of the nasal cavity's superior portion. The script describes the ethmoid bone's role in the formation of the cribriform plate, which is where the olfactory nerves pass through to the nasal cavity.

💡Sphenoid Bone

The sphenoid bone is a complex bone located deep within the skull, contributing to the back of the orbit. The script discusses the sphenoid bone's position and its importance in the structure of the orbit and the cranial cavity.

💡Palatine Bone

The palatine bones form part of the hard palate and extend into the orbit. The script mentions the palatine bone's color coding in the model and its anatomical position adjacent to the sphenoid bone within the orbit.

💡Lacrimal Bone

The lacrimal bone is a small bone in the face that forms part of the medial wall of the orbit. The script explains its role in relation to tear drainage, with the lacrimal sac and nasolacrimal duct being associated structures.

💡Fissures and Foramina

Fissures and foramina are openings in the bones that allow for the passage of nerves, blood vessels, and other structures. The script discusses several of these, including the superior and inferior orbital fissures and the supraorbital and infraorbital foramina, which are essential for the function of the extraocular muscles and sensory nerves.

💡CT Radiography

CT radiography, or computed tomography, is a medical imaging technique that provides detailed cross-sectional images of the body. The script mentions CT as the preferred method for assessing blowout fractures, offering more detailed information than traditional X-ray imaging.

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]