20/11/19 eye Flashcards
What are the three layers of the eye?
- Outer fibrous
- Vascular
- Inner retina
Components of the fibrous layer?
- Outermost layer of the fibrous layer is the sclera
- the sclera is continuous with the other layer, the cornea.
Functions of the Sclera (outermost layer of fibrous layer)?
- protection
- anchoring for extrinsic eye muscles
shape of eye
Functions of cornea (other layer of fibrous layer along with sclera)?
- cornea is the bulge at the front of the eye, this refracts light.
- no blood vessels, want to be clear so you can see.
- innervated
Interesting fact about the cornea (other layer of fibrous layer along with sclera)?
The cornea is the only tissue you can replace or transplant without fear of rejection - due to the cornea having no blood vessels and being out of reach of immune system.
Components of the vascular layer?
Choroid (back of lense)
Ciliary body
- smooth muscle
- ciliary processes
- ciliary zonules
Iris
Functions of the Choroid (part of vascular layer, along with ciliary body and iris)?
- blood vessel rich
- provides nutrients for all layers
- melanocytes produce brown pigment, absorbs light coming in.
Functions of the Ciliary body (part of vascular layer, along with choroid and iris)?
- ciliary muscle, a type of smooth muscle.
- ciliary processes, small finger-like protrusions (produce fluid that fills anterior segment of eye and connects to ciliary zonules.
- ciliary zonules, pull on lens to change shape.
Functions of the Iris (part of vascular layer, along with choroid and Ciliary body)?
Has 2 layers of smooth muscle.
- outermost is dilator pupillae (dilates pupil - hole larger) (smooth muscle fiber orientated outward). Part of sympathetic NS
- Sphincter pupillae, circularly orientated smooth muscle fibers, constrict pupil. part of parasympathetic NS.
Explain relationship between the Iris and melanocytes.
Melanocytes are within and surrounding the iris.
Melanocytes produce brown pigment. Amount of brown pigment determines eye color.
Babies often have blue eyes, as the brown pigment hasn’t developed yet.
Components of the inner retina (innermost layer of the eye)?
Has 2 layers: outer pigmented layer: - has blood vessels and pigment. - has 3 types of cells. - anterior region is called the optic disc (where optic nerve leaves eye AKA blind spot).
Neural layer of retina:
- light hits photoreceptors first after passing through other cells. Photorecptors then transfer info to bipolar cells, then ganglion cells, then ganglion (with long arse axons) carry info to brain as they leave optic nerve.
- has rods and cones
-
3 types of cells in the retina?
- Photoreceptors
- bipolar cells
- ganglion cells
- light passes through ganglion and bipolar cells before hitting photoreceptors first.
What is the optic nerve?
Collection of ganglion cell axons.
Signal output and pathway of light run in opposite directions
:)
Functions of rods (component of neural layer of retina)?
- sensitive to light change, important in dim light.
- more rods than cones in cells.
- found in periphery of retina.
Are rods or cones responsible for color and shape vision?
Cones
Functions of cones (component of neural layer of retina)?
- Used in bright line
- for color and sharp vision
Are cones distributed uniformly in the retina?
No, highest concentration of cones in fovea centralis of macula lutea (region of indentation, the pit is the fovea centralis).
Interesting fact about the retina?
All other cells are pushed aside so light can directly hit cones, this allows for sharp vision.
Anterior portion of the eye?
Is everything in front of eye and has 2 chambers.
anterior chamber:
- in front of iris
posterior chamber:
- behind iris, around lens.
- aqueous humor, from ciliary processes, secreted into posterior chamber.
fluid secreted in anterior portion/segment of eye
aqueous humor, from ciliary processes, secreted into posterior chamber of anterior segment by passing over iris and through pupil.
- gives nutrients and removes waste.
- drains into scleral venous sinus (drain fluid back into heart).
Why does glaucoma occur?
Fluid produced faster than it is being drained. Due to block of scleral venus sinuse.
Too much aqueous humor
= pressure on structures
= structural damage (to optic nerve)
Eye drops clear blockages.
Posterior portion of the eye?
Everything behind lens.
+
Vitreous humor
- shape of eye
- keeps eye clear, so light can transmit
- pushes neural layer against vascular layer (back of eye).
does aqueous humor (anterior segment) or vitreous humor (posterior segment) last longer
Vitreous humor forms in embryo and lasts a lifetime.
VS
aqueous humor which is constantly regenerated.
Functions of the lens?
- avascular, made of crystalline (onion looking protein)
- can change shape, due to cilliary zonules pulling on it.
Explain cataracts.
Excessive accumulation of crystalline protein.
The number of crystalline increase over time making lens less flexible
= worse vision.
