Intro to the Eye Flashcards
What are the layers of the eye?
Outer Fibrous Coat
- Cornea Anteriorly
- Sclera Posteriorly & Laterally
Vascular Coat:
- Iris & Pupil
- Ciliary Body
- Choroid
Sensory Coat:
- Retina
What are the histological layers of the Cornea?
- Stratified Squamous non-keratinized Epithelium
- Bowman’s Membrane (basement membrane)
- Stroma (regular connective tissue - collagen)
- Descemet’s Layer (basement membrane)
- Endothelium (single layer)
What would be the reason for examining Bowman’s membrane in an ocular injury?
It the injury only affects the epithelium it will heal to normal.
If it breaks the bowmans membrane then it will heal with collagen and form a scar, affecting corneal transparancy and therfore sight
How do we maintain corneal transparency?
- No blood vessels in the stroma
- Regular arrangement of the stroma
- Pumps in the endothelium keep out the aqueous humor
How does nutrition reach the cornea?
From the:
- Tear Film
- Blood vessels in the sclera
- Aqueous Humor
How is the avascular nature of the cornea relevant to surgery?
Because its avascular theres a low chance of foreign antigens being noticed, this means theres a lower chance of corneal graft rejection than any other type of transplant.
This has led to the cornea being dubbed an “immune-privileged” site
How do we divide up the eye (segments/chambers)
Anterior Segment and Posterior Segment divided by the lens.
The anterior segment is split into the ant/post chambers divided by the iris.
Where is aqueous humor produced/
The ciliary body in the posterior chamber of the anterior segment
Explain the passage of aqueous humor
- Produced in the ciliary body
- Passes between lens and iris into anterior chamber
- Then drains through the trabecular meshwork and out schlemm’s canal
What is the choroid?
A part of the vascular coat.
Its a layer of fenestrated blood vessels of varying diameter below the retina
Explain the layers of the retina?
Split into 10 layers, these are not all separate cell layers, the organisation of the cells make them appear like 10 layers.
The important layers are:
10) Pigment Epithelial layer
9) Rods and cones layer (dendrites of the lowest neuron layer)
2) Nerve Fibre layer (Axons of the highest neuron layer)
Explain the blood supply of the retina?
- Outer layers are supplied by the choroid by diffusion
- Inner Layers are supplied by branches of the central retinal artery
What do you see with an opthalmoscope
The retina and its blood vessels (branches of the central retinal artery)
What is special about the central part of the retina?
Fovea Centralis!
It has the densest packing of cones/rods anywhere in the retina so its where the image is sharpest.
The outer layers of the retina are also pushed aside at the fovea centralis to expose the rods/cones.
What suspends the lens?
Suspensory Ligaments (Zonules)
