Special Senses 2 Flashcards
Name the 3 layers of the eye
- Outermost is the corneoscleral coat
- Middle is the uveal tract (vascular coat)
- Inner layer is the retina (nerve cells)
Describe the shape of the lens
It is biconvex and elastic
What exists in front of the lens
Two chambers filled with aqueous humor:
- Anterior chamber
- Posterior chamber
What exists behind the lens
Large vitreal cavity filled with vitreous humor
What is the conjunctiva
A thin, transparent mucous membrane
Describe the layers of the conjunctiva
- Stratified columnar epithelium with goblet cells
2. Lamina propria with loose connective tissue
Name the 5 layers of the cornea
- Epithelium
- Bowman’s membrane (collagen)
- Cornea stroma (collagen)
- Descemet’s membrane (collagen)
- Endothelium
Describe the epithelium of the cornea
Non-keratinised stratified squamous
What is the cornea stroma consisted of
Many layers of precisely orientated, hydrated collagen with each layer at roughly right angles to each other
What is the sclera
Tough coat of collagen and elastic fibres
What does the ciliary body contain
Smooth muscle that allows the lens to change shape
How is excess fluid drained from the anterior chamber
It is drained via the canal of Schlemm into blood vessels
What is the iris composed of
Mostly loose connective tissue with a layer of pigmented epithelium on its posterior surface (contains melanocytes)
Name the muscles of the iris
- Sphincter pupillae
2. Dilator pupillae
Describe lens fibres
Long, thin cells that, as they mature, lose their nuclei and most organelles
What is the subcapsular epithelium
Layer of simple cuboidal epithelium that covers the lens anteriorly
What is the retina
A complex, thin layer of nervous tissue lining the inner eye
What does each retina contain
- 130 million rods
2. 6.5 million cones
What does each rod contain
Rhodopsin, a light-sensitive pigment
What does each cone contain
One of three opsin pigments, sensitive to either: red, green, or blue light
Are rods and cones evenly distributed
No
Describe the distribution of rods
They predominate away from the fovea but are absent in the fovea
Where does the fovea lie
At the centre of the optical axis, on the retina, at the centre of the macula lutea
What is at the centre of the fovea
The foveola, where the retina thins and is avascular
What is the optic disc
The site where the axons of the retinal ganglion cells exit the eye to form the optic nerve
What do the retinal ganglion cells have to pass through to form the optic nerve
Through the sclera; specifically the lamina cribrosa
Why is the optic disc also known as the blind spot
It lacks photoreceptors
