Eye Flashcards
What are the three layers of the eye
Corneoscleral coat, uveal tract and retina
What is the cornea
A transparent anterior extension of the sclera
What does the uveal tract consist of
Anteriorly - iris and ciliary body
Posteriorly - vascularised choroid coat
What does the retina consist of
Layers of nerve cells, their processes, support cells and on the outside, a layer of pigmented epithelium
What allows the lens to change shape
Its elasticity
What does the change in shape of the lens allow
Accommodation for near vision
What is in front of the lens
Anterior and posterior chambers
What fills the anterior and posterior chambers
Aqueous humor
What lies posterior to the lens
The vitreal cavity
What fills the vitreal cavity
Vitrius humor
Structure of vitrous cavity
Avascular and gelatinous due to collagen fibres and hyaluronic acid
What is the conjuctiva
A thin, transparent mucous membrane
What lines the conjunctiva
Stratified columnar epithelium with goblet cells, and has a lamina propria of loose connective tissue
Where does the conjunctiva run from/to
The corneosclearal margin and reflects over the inner surface of the eyelids
Composition of the cornea
Outer layer of thin non-keratinised stratified squamous epithelium sitting on a thin layer of collagen (Bowman’s membrane) composed of randomly orientated, condensed thin collagen fibrils
What is the stroma
Many layers of precisely orientated hydrated collagen
What is between the layers of the cornea
Corneal fibroblasts
What is on the inside of the cornea
Layer of endothelium sitting on a layer of meshwork collagen called Duscemet’s membrane
What causes a Kaiser-Fleischer ring
An accumulation of copper in Duscemet’s membrane
What is the sclera
A tough coat of collagen and elastic fibres defining the globe
What attaches to the sclera
The tendons of the extraocular muscles
What does the ciliary body contain
Smooth muscle
What is the function of the smooth muscle in the ciliary body
It releases tension on the zonular fibres, during near vision, allowing the lens to round-up
How is excess fluid drained from the anterior chamber
Via the canal of Schlemm
What causes glaucoma
Drainage of the anterior chamber of the eye is not adequate
What is the iris composed of
Loose connective tissue with a layer of pigmented epithelium on its posterior surface
What cell is found within the iris
Melanocytes
What is the function of the smooth muscle within the iris
Changes the iris diameter
Where are the sphincter pupillae muscles found
Near the tip of the iris
Function of sphincter pupillae muscles
Under parasympathetic innervation - constrict the pupil
Function of dilator pupillae 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
How does aqueous humor flow
From the anterior chamber to the posterior chamber
What is the lens
A transparent, biconvex structure made up of lens fibres
What are contained within the lens fibres
Proteins called crystalins
What covers the lens anteriorly
Outer connective tissue capsule and a layer of simple cuboidal epithelium
What is the retina
A complex, thin layer of nervous tissue lining the inner eye
What structures are within the retina
Rods and cones
What do rods conatin
Rhodopsin - a light sensitive pigment
What is contained within cones
One of three epsin pigments - sensitive to either red, green or blue light
What structure predominates away from the fovea
Rods
What lies at the centre of the retina
The fovea
What is at the centre of the fovea
The foveola
What happens to the retina at the foveola
It thins and becomes avascular
What structure is found at the foveola
Cones
What covers the cones at the foveola
The outer plexiform layer
What is the optic disc
The site where the axons of the retinal ganglion cells exit the eye to form the optic nerve
What must the nerves pass through to create the optic nerve
The sclera
What does the optic disc lack
Photoreceptors
What are the openings in the sclera that the axons pass through known as
Lamina cribrosa
What is the optic disc also known as
The blind spot
