chap 9

macula

area of large concentration of cones in the retina where the visual image arrives after passing through the cornea and lens

fovea

area of the highest concentration of cones found near the center of the macula - the center of color vision and the site of sharpest vision

suspensory ligaments

attach to the lens and the ciliary body - holds the lens so that light passing through the pupil passes through the center of the lens along the visual axis

nasolacrimal duct

carries tears from the lacrimal sac to the nasal cavity

pupil

central opening of the iris which light passes through before striking the lens

medial/lateral canthus

connection points of upper and lower eyelids

vascular layer

contains numerous blood vessels, lymphatic vessels, and the intrinsic eye muscles - functions include providing a route for blood vessels and lymphatic vessels that supply the tissue of the eye, regulating the amount of light entering the eye, secreting and reabsorbing the aqueous humor that circulates within chambers of the eye, and controlling the shape of the lens

inferior rectus

contraction causes the eye to look down towards the feet

lateral rectus

contraction causes the eye to look laterally or away from the nose

medial rectus

contraction causes the eye to look medially towards the nose

superior oblique

contraction causes the eye to roll, looking down and laterally away from the nose

inferior oblique

contraction causes the eye to roll, looking up and up and laterally away from the nose

optic disc

converging point of axons of ganglion cells and the origin of the optic nerve - has no photoreceptors or other retinal structures and results in light going unnoticed when it strikes the structure

palpebrae

eyelids - act like windshield wipers to keep the surface of the eye lubricated and free from debris and dust, and protect the surface of the eye

aqueous humor

fluid that circulates within the anterior cavity and some within the posterior cavity - pressure exerted by this fluid helps maintain the pressure of the eye, particularly the cornea, and helps transport nutrients and waste

vitreous humor

gelatinous substance of the posterior cavity that helps maintain the shape of the eye and also holds the retina against the choroid

cones

group of three specific types of photoreceptor that provide us with color vision, allow us clearer, sharper images, but require brighter light-

retina

innermost layer of the eye consisting of a thin outer pigment layer called the pigmented part and a thick outer pigment layer called the neural part - functions to absorb light that passes through the neural part, preventing light from bouncing back and producing visual echoes - contains photoreceptors that respond to light, supporting cells and neurons that perform preliminary processing and integration of visual information, and blood vessels supplying tissues that line the posterior cavity

posterior cavity

large posterior cavity of the eyeball filled with a small amount of aqueous humor and a larger amount of a gelatinous substance called vitreous humor

lens

lies posterior to the cornea and is held in place by suspensory ligaments - primary function is to focus the visual image on the photoreceptors of the retina by changing shape

lacrimal pores

openings in the medial canthus which allow tears to be swept through and into the lacrimal canals

ciliary body

point of attachment for the iris - contains a ring of smooth muscle that projects into the interior of the eye - attachment point of suspensory ligaments - contains muscles that contract to alter the shape of the lens

pupil

portion of the vascular layer visible through the cornea which contains blood vessels, pigment cells, loose connective tissue, and two layers of intrinsic smooth muscle fibers - when the smooth muscle fibers contract it changes the diameter of the pupil

photoreceptors

rods and cones of the retina that detect photons, basic units of visible light

anterior cavity

smaller anterior cavity of the eyeball which is divided into two chambers and contains aqueous humor

lacrimal glands

tear gland that lies superior and lateral to the eyeball- provides key ingredients and most of the volume of tears and enzymes that attack bacteria

lacrimal canals

tears are swept across the surface of the eye to the medial canthus through which the tears travel into lacrimal pores and into the

sclera

the "white of the eye" which is a layer of dense fibrous connective tissue containing both collagen and elastic fibers - site of extrinsic eye muscle insertion

fibrous layer

the outermost layer of the eye consisting of the sclera and cornea - provides mechanical support and come degree of protection, serves as an attachment point for the extrinsic eye muscles, and assists in the focusing process

conjunctiva

transparent mucous membrane that forms the inner surface of the eyelids and the outer, white surface of the eye

cornea

transparent part of the outer fibrous layer which is continuous with the sclera - first structure which light passes through when entering the eye

rods

type of photoreceptor that does not discriminate among colors of light and allow us to see in dimly lit situations