Special Senses 2 Flashcards
What are the three main layers of the eye?
Outermost (Corneoscleral coat), Middle (Uveal tract) and Innermost (Retina)
What is the cornea?
A transparent anterior extension of sclera
What does the uveal tract consist of?
Iris and ciliary body anterior and vascularised choroid coat posteriorly
What does the Retina consist of?
Layers of nerve cells, their processes support cells and a layer of pigmented epithelium
What is a biconvex lens?
Is elastic to allow it to change shape in order to permit accommodation for near vision
What are the chambers in front of the lens filled with?
Aqueous humor
Posterior to the lens, is a larger virtual cavity filled with?
Vitrous humor
Where does the cornea sit?
On the bowman membrane
What is the storma of the cornea?
Many layers of hydrated collagen
What is on the inner layer of the cornea?
A layer of endothelium sitting on a layer of collagen called Duscemet’s membrane
What is the sclera?
A tough coat of collagen and elastic fibres defining the globe
What attaches to the sclera?
Tendons of the extraocular muscles
What is the ciliary body?
Contains smooth muscle that during near visions, relates tension on the zonuar fibres allowing the lens to round-up due to its natural elasticity
What is the iris?
Mostly loose connective tissue with a layer of pigmented epithelium on its posterior surface
What does the iris contain?
Melanocytes
What happens to the eyes if there is a lot of melanocytes?
Brown eyes
What happens to the eyes if there is not a lot of melanocytes?
Blue eyes
What changes the diameter in the iris?
Smooth muscle
Where are the sphincter papillae fibres found?
Near the tip of the iris
Where is the excess fluid from the anterior chamber drained?
Canal of Schlemm into blood vessles
What results when drainage from the anterior chamber is not adequate?
Glaucoma
What is a transparent spherical structure that is made up of lens fibres?
Lens
What is the lens packed with?
Crystallins
What is the lens covered with anteriorly?
Outer connective tissue capsule and a layer of simple cuboidal epithelium
What way do the lens fibres run?
Anterior to posterior
What is the retina?
Thin layers of nervous tissue lining the inner eye
What do the rods do in the retina?
Predominate away from the fovea but are absent in the fovea
What is found in rods?
Pigment
Where does the fovea lie in the retina?
At the centre of the optical axis on the retina
What is at the centre of the fovea?
Foveola
What is only found in the foveola?
Cones
What is known as the blind spot?
Optic disc
What does the optic disc lack?
Photoreceptors
What is infront of the lens?
Anterior and posterior chambers
What lies posterior to the lens?
The virtual cavity
What is the conjuctiva?
A thin, transparent mucous membrane
What lines the conjuctiva?
Stratified squamous epithelium with goblet cells
What is between the layers of the cornea?
Corneal fibroblasts
Function of the sphincter papillae muscles?
Under parasympathetic innervation - constrict the pupil
Function of dilator papillae muscles?
Under sympathetic innervation - open the pupil
What does the ciliary body attach to and how?
To the lens by a series of zonular fibres
What do rods contain?
Rhodopsin
What happens to the retina at the foveola?
It thins and becomes avascular
What covers the cones at the foveola?
The outer plexiform layer
What are the openings in the sclera that the axons pass through known as?
Lamina cribrosa
