Question

Anatomy Tutorial: Anatomy of the Eye

Answer 1

\({\bf{Overview:}}\)



- wall of the eye has three layers: outer layer (fibrous), intermediate layer (vascular) and inner (retina)
- inside of the eye has two cavities:
> posterior (vitreous chamber), contains vitreous body
> anterior, contains aqueous humor divided into the anterior chamber (between the cornea and iris) and the posterior chamber (between the iris and lens)

\({\bf{Fibrous~Layer:}}\)
> contains sclera and cornea
> protection and attachment for extraocular muscles, aids in focusing

> sclera: white part of the eye, dense fibrous CT w/ collagen + elastin
- thick at the back of the eye near the optic nerve
- thin on the front surface
- insertion site for extra-ocular muscles
- vascular, innervated

> cornea: transparent; layer of epithelium over many collagen layers

> cornoscleral junction: junction btwn cornea + sclera. avascular; must be nourished by your tears. just like me.

Answer 2

\({\bf{Vascular~Layer:}}\) contains iris, ciliary body, choroid
- vascular
- site for blood vessels and lymphatics
- contrl amount of light entering eye
- secretion/reabsorption of aqueous humor
- control shape of lens

> iris: pigments (on surfaces), vascular, contains smooth muscle and CT
- sphincter pupillae: decreases diameter of pupil, parasympathetic
- dilator pupillae: increases diameter of pupil, sympathetic

> cilliary body: iris attaches to cilliary body
- extends to ora serrata
- ciliary muscle: ring of muscle that projects into the eye
- ciliary processes
- ciliary zonule: ring of CT fibers that holds lens in place

> choroid: vascular layer, separates fibrous layer and ora serrata
- nourishes the retina
- contains melanocytes
- attaches to outer retinal layer

Answer 3

\({\bf{Inner~Layer~(Retina):}}\) two layers (pigmented and neural)
- pigmented: absorbs light; extends over ciliary body and iris
- neural: contains photoreceptors , supporting cells, neurons, blood vessels; extends to ora serrata

photoreceptors:
- rods (detect intensity), located around the outer parts of retina
- cones (detect color) higher clarity; located on the macula (the place where the image arrives) on fovea centralis

both synapse w/ bipolar cells
- horizontal cells: controls communication between photoreceptors + bipolar cells
- bipolar cells: synapse w/ ganglion cells
- amacrine cels: control communication between bipolar + ganglion
- ganglion cells: first-order, and action potentials travel to brain --> converge onto optic disc --> optic nerve II --> diancephalon
- central retinal artery + vein: pass thru optic nerve onto the optic disc "blind spot" with no photoreceptors

Answer 4

\({\bf{Aqueous~Humor:}}\) ISF enters posterior chamber of the eye --> becomes aqueous humor --> protection and pathway for moving nutrients/waste products --> anterior chamber --> reabsorption thru scleral venous sinus

\({\bf{Vitreous~Humor:}}\) supports the structural position/integrity of lens + retina

\({\bf{Lens:}}\)
- covered w/ dense elastic fibrous capsule
- outer fibers interact w/ ciliary zonule fibers --> lens flattens --> can focus on objects that are farther away
- ciliary muscles contract --> ciliary body moves towards lens --> reduction of tension --> lens begins to form more spherical shape --> focus on objects closeby

Answer 5

Adapted from Human Anatomy, Martini, et. al. 9th edition