Special Senses 2 Flashcards
The Eye - Layers
Corneoscleral coat
Outermost later. Cornea is transparent anterior extension of sclera
The Eye - Layers
Uveal tract
Middle layer. Consists of iris and ciliary body anteriorly and vascularized choroid coat posteriorly
The Eye - Layers
Retina
Inner layer consisting of layers of nerve cells, their processes, support cells and, on the outside, a layer of pigmented epithelium
The Eye - Layers
Biconvex Lens
Present along with layers. Elastic, allowing it to change shape to permit accomodaton for near vision
The Eye - Layers
Anterior and Posterior chambers
Sit in front of the lens and are filled with aqueous humor. Posterior to the lens is the bigger vitreal cavity full of vitrious humor which is avascular and gelatinous
The Cornea
Outer layer
Thin stratified squamous epithelium on thin layer of collagen called Bowman’s membrane.
The Cornea
Stroma
Makes up most of the thickness of the cornea. Made of many laters of precisely oriented, hydrated collagen
The Cornea
Duscemet’s membrane
Inside of the layers. Endothelium sitting on a layer of collagen.
Anterior of the Eye
Sclera
Tough coat of collagen and elastic fibres defining the globe. Tendons of the extraocular muscles attach to sclera
Anterior of the Eye
Ciliary body
Contains smooth muscle that, during nearvision, releases tension on the zonular fibres allowing the lens to round-up due to its natural elasticity
Anterior of the Eye
Excess fluid from anterior chamber
Drained via the canal of schlemm into blood vessels. Glaucoma results when this drainage is not adequate
Anterior of the Eye
Iris
Mostly loose connective tissue with a layer of pigmented epithelium on its posterior surface. Contains melanocytes.
Anterior of the Eye
Iris muscle
Contains smooth muscle that changes it’s diameter
Anterior of the Eye
Dilator pupillae
Muscles are radially oriented and, under sympathetic stimulation, they open the pupil
Anterior of the Eye
Sphincter pupillae
Fibres located near the tip and are circumferentially oriented. Constrict pupil under parasympathetic stimulation
Lens
What is it?
Transparent spherical structure made up of lens fibres.
Lens
Lens Fibres
Lens fibres are long cells that lose their nuclei as they mature, and most organelles are packed with proteins called crystallins.
Lens
Anterior covering
Anteriorly, the lens is covered by an outer connective tissue capsule and a layer of simply cuboidal epithelium.
Retina
What is it?
Complex, thin layer of nervous tissue lining the inner eye. Within the retina is a characteristic layered structure
Retina
Rods and cones
Distribution of these is not uniform. Rods predominate away from the fovea but are absent at the fovea.
Fovea of Retina
Foveola
Fovea is at the centre of the optical axis on the retina. At the centre of the fovea is the foveola. The retina thins and is avascular at the foveola, and there are only cones found here covered by the outer plexiform layer
Retina
Optic disc
Lacks photoreceptors. Otherwise known as the “blind spot”.
