Ch. 7.7 Special Senses Key Terms
aqueous humor
A clear, watery fluid that fills the space between the cornea and iris. It helps maintain the forward curvature of the eyeball and refracts light rays.
conjunctiva
A mucous membrane that lines the eyelids and covers the front of the eye to provide additional protection and lubrication.
lens
A circular structure located behind the pupil and suspended in position by ligaments. It refracts (bends) light rays so the rays focus on the retina.
refracts
Means to bend light rays, a function performed by the lens, cornea, aqueous humor, and vitreous humor so that the light rays focus on the retina.
vestibule
The first section of the inner ear, which acts as the entrance to the two other parts of the inner ear
auditory canal
A canal, or tube, in the outer ear that leads from the pinna to the tympanic membrane. Special glands in this canal produce cerumen, a wax that protects the ear.
cornea
A circular, transparent part of the front of the sclera. It allows light rays to enter the eye.
organ of Corti
A receptor of sound waves composed of delicate, hairlike mechanoreceptor cells located within the cochlea of the inner ear. It transmits the impulses from sound waves to the auditory nerve.
retina
The innermost layer of the eye, made of many layers of nerve cells, which transmit the light impulses to the optic nerve. It contains cones and rods
vitreous humor
The jellylike substance that fills the area behind the lens. It helps maintain the shape of the eyeball and also refracts light rays.
auricle
The visible part of the outer ear, also called the pinna. It is elastic cartilage covered by skin.
eustachian tube
A tube that connects the middle ear to the pharynx, or throat. This tube allows air to enter the middle ear and helps equalize air pressure on both sides of the tympanic membrane.
ossicles
The three small bones (malleus, incus, and stapes) in the middle ear. They are connected and transmit sound waves from the tympanic membrane to the inner ear.
sclera
The outermost layer of the eye, made of tough connective tissue, frequently referred to as the "white" of the eye. It maintains the shape of the eye.
choroid coat
The middle layer of the eye, which is interlaced with many blood vessels that nourish the eyes.
iris
The colored portion of the eye. It is located behind the cornea on the front of the choroid coat. It contains two muscles, which control the size of the pupil and regulate the amount of light entering the eye.
pinna
The visible part of the outer ear, also called the auricle. It is elastic cartilage covered by skin.
semicircular canals
Structures located in the inner ear that contain a liquid and delicate, hairlike cells that bend when the liquid moves with head and body movements.
cochlea
A snail's shell-shaped structure in the inner ear that contains delicate, hairlike mechanoreceptor cells, which compose the organ of Corti, a receptor of sound waves.
lacrimal glands
Glands in the eye that produce tears, which constantly moisten and cleanse the eye.
pupil
The opening in the center of the iris. Its size is controlled by the muscles of the iris, which regulate the amount of light entering the eye.
tympanic membrane
The eardrum, which separates the outer ear from the middle ear. It vibrates when sound waves hit it and transmits the sound waves to the middle ear.