Lecture 32 DA Flashcards
Where is the supraorbital margin?
The frontal bone directly under the eyebrow, forming a ridge.
What is the dint above the supraorbital margin called, and what passes here?
Supraorbital notch. Neurovascular vessels to the forehead pass here.
Where is the infraorbital margin? What forms it.
Directly inferior to the eyeball. Formed by zygomatic bone laterally and maxilla medially.
What is the superior roof of the orbit?
Orbital plate of the frontal bone.
What forms the posterior wall of the orbit?
Lesser wing of sphenoid laterally, and ethmoid bone medially.
What can be found on the medial wall of the orbit?
Ethmoid bone and lacrimal bone.
What is the structure of the ethmoid bone like?
Very thin, called papyrus region for this reason.
What forms the floor of the orbit?
Maxilla medially, zygoma laterally, and palatine superior to the two.
What can be found on the lateral wall of the orbit?
Zygomatic bone.
Why do some bones in the orbit break so easily?
They break to protect the eye so pressure doesn’t damage it.
What passes through the optic canal?
Optic nerve with the ophthalmic artery.
What nerves pass through the superior orbital fissure?
Ophthalmic division of the trigeminal nerve and extraocular muscle nerves.
What forms the superior orbital fissure?
Gap between lesser and greater wing of sphenoid.
Where is the inferior orbital fissure?
Inferior to the superior orbital fissure.
What are the three layers of the eye?
Outer coat
Cornea/sclera
Middle layer
Uvea
Inner coat
Retina
What is the purpose of the sclera?
Strength, is very tough and durable. Maintains shape, attachment for muscles and resists forces.
What is the purpose of the uvea?
Mostly supplies nutrition to the eye.
What is the purpose of the retina?
Vision.
How much of the eye is the sclera?
Posterior 5/6ths, and is white.
What is the cornea and sclera made of?
Collagen.
Is the cornea vascular?
No.
How much of the eye is the cornea?
Anterior 1/6th.
What are the layers of the cornea?
Epithelial layer
Stroma - collagen
Endothelium
Whats so special about the endothelium?
Its unique, and are born with a certain number. Maintains water balance and cornea thickness. Doesn’t regenerate.
Why is the cornea transparent if it and the sclera both have collagen?
Collagen in the cornea is parallel, ordered and stacked at a different angle over one another with all the same size.
The sclera has a whorly arrangement with different sizes, unordered and random.
What is the anterior chamber angle, and what does it do?
Juntcion between cornea and iris. Aqueous humour drains out of the eye here.
What is the trabecular meshwork? Where does it drain to?
A sieve-like structure that drains the eye, and drains into Schlemm’s canal inferiorly.
Where is the aqueous humour formed?
In the ciliary body of the uvea.
What tether’s the lens?
Ciliary processes (ciliary epithelium) of the uvea, via zonules (ligaments).
What do ciliary muscles allow the eye to do?
Accomodation.
What other fluid is aqueous humour like?
Cerebrospinal fluid.
Does aqueous humour have protein?
Very little.
What does the aqueous humour do?
Provides nutrition and intraocular pressure.
What is accomodation?
Ability to focus on something close up.
What is involved in accomodation?
Ciliary muscles and their ligaments called zonules attaching to the lens.
Is ciliary muscle contraction voluntary?
No, it is smooth muscle.
What happens to the lens when ciliary muscles contract?
The zonules aren’t under tension, and the lens becomes fat and wider, focusing closer.
What happens to the lens when ciliary muscles relax?
Zonules are under tension, and the lens becomes thin and narrow.
What is the iris?
Coloured aperture of the eye.
What two muscles forms the iris, which is anterior and posterior?
Sphincter pupillae - Anterior
Dilator pupillae - Posterior
What is the function and innervation of the two iris muscles?
Sphincter pupillae - constricts the eye, parasympathetic innervation.
Dilator pupillae - dilates the eye, sympathetic innervation.
