Anatomy and Physiology 2 Chapter 17 - Internal Eye Anatomy

4 things about the eye (organ) anatomy

1. sophisticated visual instrument

2. each eyeball slightly irregular spheroid

3. sits in orbit with extrinsic eye muscles, lacrimal gland, and cranial nerves

4. orbital fat cushions and insulates

what are the 2 cavities of the eye

1. anterior cavity (includes the aqueous humor, posterior chamber, and anterior chamber)

2. posterior cavity (includes the vitreous humor)

anterior cavity

region with aqueous humor whose pressure maintains/stabilizes shape and acts as nutrient and waste transport

aqueous humor

maintain and stabilize shape of anterior region of the eyeball; gives pressure

posterior chamber

makes aqueous humor via ciliary processes; diffuses it through retina and moves through pupil to anterior chamber

posterior cavity

region with vitreous humor

vitreous humor

gelatinous mass with fluid portion (humor); made of collagen fibers, stabilizes shape of eye, formed during development and not replaced

3 layers of the tunica

1. fibrous layer (outer layer) - includes the sclera and cornea

2. uvea (vascular layer) - includes the iris (pupillary constrictor and dilator) , ciliary body (ciliary processes and zonule), and choroid

3. retina (neural layer)

sclera (white)

dense vascular fibrous connective tissue for protection and anchoring

cornea (transparent)

continuous with sclera, bends light; no blood vessels (diffusion of nutrients in tears), dense collagen fibers oriented to not block light, many free nerve endings

iris

pigmented, flattened ring; 2 pupillary muscle layers that change pupil diameter (outer dilators and inner sphincters), surrounds open space (pupil), and regulates amount of light entering

pupillary constrictor (sphincter)

part of the iris

touches the pupil, contract = constricter expands, showing less of the eye when there’s lots of light or looking at something close, parasympathetic division

pupillary dilator (radial)

part of the iris

runs in opposite direction on the constrictor, contract = pulls everything back, showing more of the eye when there’s low levels of light or looking at something far away, sympathetic division

ciliary body

mostly ciliary muscle; attached to ora serra (posterior) and lens (anterior)

ciliary processes

part of the ciliary body

creates the aqueous humor

suspensory ligaments (ciliary zonule)

part of the ciliary body

attach to lens and allows shape of the lens to change and comes off ciliary processes

choroid

vascular layer separates fibrous from inner layer attached to retina; provides blood to all layers and prevents light scattering due to pigmentation

retina

visual detection layer; pigmented and neural layer

macula

highest density of cones and photoreceptors

fovea

only has cones to detect colors

pigmented layer

keeps light from bouncing out of neural layer; touches the choroid, prevents light from scattering, stores vitamin A to create retinal, and phagocytizes photoreceptor fragments

what are the 4 cells in the neural layer

1. photoreceptors (detect photons)

2. bipolar cells

3. fine-tuning cells (horizontal and amacrine cells which fine tune info from photoreceptors)

4. ganglion cells/optic disc (ganglion cells converge at the optic disc, no photoreceptors, and forms blind spot)

cones

detect color

rods

detect light and dark