H&N 6.1 the orbit Flashcards Preview

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Flashcards in H&N 6.1 the orbit Deck (59)
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What bones make up the orbit?



What bones make up the lateral orbit?

spenoid, zygomatic


What bones make up the roof of the orbit?



What bones make up the medial border of the orbit?



What bones make up the floor of the orbit?



Which wall of the orbit is the weakest?

The floor of the orbit.


What openings are there into the orbit?

-optic canal
-superior orbital fissure
-inferior orbital fissure


What runs through the optic canal?

-optic nerve (CN II)
-central retinal artery,
-central retinal vein.


What structures run through the superior orbital fissure?

-occulomotor nerve (CN III) (sup and inf. branches)
-trochlea nerve (CN IV)
-abducens nerve (CN VI)
-opthalmic branches of the trigeminal nerve (lacrimal, frontal, nasocilliary)
-superior opthalmic vein.


What structures run through the inferior orbital fissure?

-inferior opthalmic vein.


What main structures make up the eyeball?

-cilliary bodies


What is the function of the lens?

-it focus' light into the eye and onto the retina.


How is the lens held in place?

By suspensory ligaments, the cilliary bodies.


What is the coloured part of the eye known as?



Why is the pupil black?

Because it is emitting no light, and absorbing lots of light, hense we see it as black.


What is the function of the cilliary bodies?

They alter the thickness of the lens, allowing us to focus our eyes, eg on close or distant objects.


What is the function of the retina?

It's there the cone cells are found, which allow us to see.
You get conversion of light energy into chemical impulses which travel to the brain via the optic nerve, allowing us to build a picture.


What is the blind spot?

Where the optic nerve enters the orbit there are no cone cells, so you cannot see.
its found where the optic disc is.
Everyone has one on each eye.


What are the 3 layers of the coverrings of the eyeball?

-outer fibrous= sclera/cornea
-middle vascular= choroid.
-inner layer- retina.


Why is the outer fibrous layer split into sclera and cornea?

Theyre the same except the cornea is transparent, allowing light to pass into the lens.
If it wasnt transparent, and what the same colour as the fibrous sclera we wouldnt be able to see.


What is the function of the outer fibrous layer of the eyeball?

It maintains the shape of the eye.


How do we examine the eye?

-fundoscope (allows visual)
-eye movements
-visual acuity
-visual fields


What structures do you see using a fundoscope?

-optic disc (always medial)
-macula + fovea (area of highest visual acuity)
-arteries and veins of the eye


What is retinal detachment and what is the cause?

Commonly caused by trauma, there is detachment of the retina from the underlying layers of the orbit (the choroid).

If you used a fundoscope, the image would be occluded because of the detached retina.

There will be interrupted supply od blood and nutrients to the retina, as this is supplied by the vascular layer so this needs correcting quickly, otherwise partial blindness can occur,


What are the coverrings of the optic nerve, and how is this clinically relevant?

-dura mater
-arachnoid mater
-pia mater.

continuation of the brain so coverred in meninges, can become inflamed in meningitis, which is what causes the associated photobia.


How can the eye be compartmentalised?

-into anterior and posterior segment.

Anterior can be further divided into anterior and posterior chambers.


Where is the anterior chamber of the eye found and what does it contain?

-found between the cornea and the lens,
contains aqueous humour.


What is the function of aqueous humour?

To supply nutrients to the cornea and lens, which are both avascular (allowing them to be transparent).


Where does the anterior chamber of the eye drain?

Aqueous humour drains via the trabecular meshwork.


What happens when there is blockage of the trabecular meshwork of the eye?
What is this more commonly known as?

You get a build up of aqueous humour which can lead to oedema of the eye and also begin to compress the posteiror segment, causing compression of the blood supply and optic nerve, which can lead to vision loss.

Open angle glaucoma.

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