Chabner's Language of medicine, 9th edition. Keywords for Chapter 18- sense organs.
accomodation
normal adjustment of the eye to focus on objects from far to near. The ciliary body adjusts the lens (rounding it) and the pupil constricts. When the eye focuses from near to far, the ciliary body flattens the lens and the pupil dilates.
biconvex
consisting of two surfaces that are rounded, elevated, and curved evenly, like part of a sphere.
choroid
middle vascular layer of the eye, between the retina and sclera; a dark brown membrane that contains many blood vessels
ciliary body
Structure surrounding the lens that connects the choroid and iris. It contains ciliary muscles, which control the shape of the lens, and it secretes aqueous humor.
cone
Photoreceptor cell in the retina that transforms light energy into a nerve impulse. These are responsible for color and central vision.
cornea
Fibrous transparent layer of clear tissue that extends over the anterior portion of the eyeball.
iris
Pigmented (colored) layer that opens and closes to allow more or less light in the eye. The central opening of this is the pupil.
lens
transparent bioconvex structure behind the pupil of the eye. It bends light rays to bring them into focus on the retina
macula
yellowish region on the retina lateral to and slightly below the optic disc; contains the fovea centralis, which is the area of clearest vision.
optic disc
Region at the back of the eye where the optic nerve meets the retina. It is the blind spot of eye because it contains only nerve fibers, no rods or cones, and is thus insenseitive to light.
pupil
central opening of the eye, surrounded by the iris, through which light rays pass. It appears dark.
refraction
Bending of light rays by the cornea, lens, and fluids of the eye to bring the rays into focus on the retina.
thalamus
Relay center of the brain. Optic nerve fibers pass through this on their way to the cerebral cortex .
vitreous humor
soft, jelly-like material behind the lens in the vitreous chamber; helps maintain the shape of the eyeball
Auditory nerve fibers
Carry impulses from the inner ear to the brain (cerebral cortex). These compose the vestibulocochlear nerve (cranial nerve VIII).
labyrinth
maze-like series of canals of the inner ear.This includes the cochlea, vestibule, and semicircular canals
vestibule
central cavity of the labyrinth, connecting the semicircular canals and the cochlea. Contains two structures; the saccule and utricle, that help maintain equilibrium.
conjunctiva
A membrane lining the inner surfaces of the eyelids and anterior portion of the eyeball over the white of the eye.