Flashcards in 3 Veterinary Term: Eyes and Ears (not done) Deck (126):
The eye and the ear are what type of organs?
What are sense organs?
are receptors whose sensitive cells may be activated by a particular form of energy or stimulus in the external or internal environment.
The sensitive cells in the eye and ear respond to a stimulus by?
initiating a series of nerve impulses along sensory nerve fibers that lead to the brain.
No matter what stimulus affects a particular receptor, the sensation felt is determined by what?
regions in the brain connected to that receptor.
mechanical injury that stimulates receptor cells in the eye and ear produces what?
sensations of vision (flashes of light) and sound (ringing in the ears).
If one could make a nerve connection between the sensitive receptor cells of the ear and the area in the brain associated with sight it would be possible to what?
perceive, or “see,” sounds.
What is the Pupil?
the dark opening of the eye where light rays enter
What is the iris?
the colored portion of the eye surrounding the pupil
What is the conjunctiva?
membrane lining the inner surfaces of the eyelids and anterior portion of the eyeball over the white of the eye.
The conjunctiva is clear and colorless except when blood vessels are dilated.
Dust and smoke may cause the blood vessels in the eye (conjunctiva) to do what?
dilate, giving the conjunctiva a reddish appearance—commonly known as bloodshot eyes.
What is the Cornea?
is a fibrous, transparent tissue that extends like a dome over the pupil and colored portion of the eye.
Light passes through cornea before passing through pupil when entering the eye.
What is the function of the Cornea?
is to bend, or refract the rays of light, so they are focused properly on the sensitive receptor cells in the posterior region of the eye.
What is avascular?
Having no blood vessels
A normal, healthy cornea is what?
avascular (has no blood vessels) but receives nourishment from blood vessels near its junction with the opaque white of the eye, the sclera.
What is the Sclera?
the opaque white of the eye.
is a tough, fibrous, supportive connective tissue that extends from the cornea on the anterior surface of the eyeball to the optic nerve in the back of the eye.
What is the choroid?
is a dark brown membrane inside the sclera.
It contains many blood vessels that supply nutrients to the eye.
The choroid is continuous with what other parts of the eye?
is continuous with the pigment‐containing iris and the ciliary body on the anterior surface of the eye.
Describe the Iris in relation to the Pupil
The iris is the colored portion of the eye, which has as a circular opening in the center that forms the pupil.
How is the amount of light entering the eye regulated?
Muscles of the iris constrict the pupil in bright light and dilate the pupil in dim light.
The ciliary body surrounds what?
surrounds the outside of the lens in a circular fashion for 360 degrees.
What are zonules?
are fine thread‐like attachments, which connect the ciliary body and the lens and allow the muscles in the ciliary body to adjust the shape and thickness of the lens.
The changes in the shape of the lens of the eye cause what?
refraction of light rays.
What is Refraction?
is the bending of rays as they pass through the cornea, lens and other tissues.
Muscles of the ciliary body produce?
produce flattening of the lens (for distant vision) and thickening and rounding (for close vision) (This refractory adjustment for close vision is accommodation.)
What is aqueous humor?
A fluid secreted by the ciliary body.
aqueous humor is found where?
in the anterior chamber of the eye.
Aqueous humor maintains what?
the shape of the anterior portion of the eye and nourishes the structures in that region.
The fluid is constantly produced and leaves the eye through a canal that carries it into the blood stream.
What is the vitreous chamber?
is a large region (cavity) behind the lens filled with a soft, jelly‐like material, the vitreous humor.
What is vitreous humor?
soft, jelly‐like material in the vitreous chamber
Vitreous humor maintains what?
the shape of the eyeball and is not constantly reformed.
Its escape (due to trauma or surgical damage) may result in significant damage to the eye, leading to possible retinal damage and blindness.
Both the aqueous and the vitreous humors further refract light rays.
What is the Retina?
is the thin, delicate and sensitive nerve layer of the eye.
What happens to light energy, in the form of waves, as it travels through the eye?
it is refracted (by the cornea, lens and fluids), so that it focuses on sensitive receptor cells of the retina called the rods and cones.
What are rods and cones?
sensitive receptor cells of the retina
What happens when light rays are focused on the retina?
a chemical change occurs in the rods and cones, initiating nerve impulses that then travel from the eye to the brain via the optic nerve.
What is the optic disc?
The region in the eye where the optic nerve meets the retina.
Because there are not light receptor cells in the optic disc, it is known as what?
as the blind spot of the eye.
What is the macula?
is a small, oval yellowish area to the side of the optic disc.
What is the fovea centralis?
a central depression contained within the macula.
The fovea centralis is composed of what?
composed largely of cones and is the location of the sharpest vision in the eye.
If a portion of the fovea or macula is damaged, what happens?
vision is reduced and central‐ vision blindness occurs.
What is the fundus?
is this posterior, inner part that is visualized through the ophthalmoscope.
Area behind the cornea and in front of the lens and iris.
It contains aqueous humor.
Fluid produced by the ciliary body and found in the anterior chamber. A humor (Latin humidus means moist) is any body fluid, including blood and lymph
Middle, vascular layer of the eye, between the retina and the sclera
Structure on each side of the lens that connects the choroid and iris.
It contains ciliary muscles, which control the shape of the lens, and it secretes aqueous humor
Delicate membrane lining the eyelids and covering the anterior eyeball
Fibrous transparent layer of clear tissue that extends over the anterior portion of the eyeball. Derived from the Latin corneus, meaning horny, perhaps because as it protrudes outward, it was thought to resemble a horn
Tiny pit or depression in the retina that is the region of clearest vision
Fundus of the eye
Posterior, inner part of the eye
Colored pigmented membrane surrounding the pupil of the eye.
Transparent, biconvex body behind the pupil of the eye. It bends (refracts) light rays to bring them into focus on the retina
Yellowish region on the retina lateral to and slightly below the optic disc; contains the fovea centralis, which is the area of clearest vision
Cranial nerve carrying impulses from the retina to the brain (cerebral cortex).
Dark opening of the eye, surrounded by the iris, through which light rays pass
light‐sensitive nerve cell layer of the eye containing photoreceptor cells
Tough, white outer coat of the eyeball
Soft, jelly‐like material behind the lens in the vitreous chamber; helps maintain the shape of the eyeball
Ex: Aqueous humor
Eyelid (see also palpebr/o)
Pupil (see also pupill/o)
Ex: Anisocoria (anis/o means unequal)
Cornea (see also kerat/o)
Ex: Corneal abrasion
Tears, tear duct (see also lacrim/o)
Lens of the eye
Sclera (white of the eye)
Uvea; vascular layer of the eye
Ex: Vitreous humor
Ex: Miosis (contraction of the pupil)
Ex: Mydraisis (enlargement of pupils)
Clouding of the lens, causing decreased vision
Increased intraocular pressure results in damage to the retina and optic nerves with loss of vision
Inflammation of eyelid, causing redness, crusting and swelling along lid margins
Inversion of the eyelid, causing the lashes to rub against the eye; corneal abrasion may result
Dropping of upper lid margin as a result of neuromuscular problems
Repetitive rhythmic movements of one or both eyes
Two layers of the retina separate from each other.
Trauma to the eye, head injuries, bleeding, scarring from infection, or shrinkage of the vitreous humor can produce holes or tears in the retina and result in the separation of layers.
Abnormal deviation of the eye
Sound waves are received by what?
The outer ear, conducted to special receptor cells within the ear and transmitted by those cells to nerve fibers that lead to the auditory region of the brain in the cerebral cortex.
Sensations of sound are perceived within?
the nerve fibers of the cerebral cortex.
What are the three separate regions the ear is divided into?
What are the functions of the outer and middle ear?
function in the conduction of sound waves through the ear.
What is the function of the inner ear?
contains structures that receive the auditory waves and relay them to the brain.
What is the pinna or auricle?
is the projecting part, or flap of the ear.
Where sound waves enter the ear.
What is the auditory meatus (auditory canal)?
leads from the pinna and is lined with numerous glands that secrete a yellowish‐brown, waxy substance called cerumen.
What is cerumen and what's it's function?
a yellowish‐brown, waxy substance.
lubricates and protects the ear.
What is the tympanic membrane or eardrum?
a membrane between the outer and middle ear.
Sound waves travel through the auditory canal and strike this.
What are ossicles?
Three small bones that move as the eardrum vibrates and conduct the sound waves through the middle ear.
List the three ossicles in the order of their vibrations
malleus, incus and the stapes.
What is the oval window?
A membrane that separates the middle from the inner ear.
S touched by the stapes as it moves.
Sound vibrations, having been transmitted by the movement of the eardrum to the bones of the middle ear, reach the inner ear via?
the fluctuations of the oval window that separates the middle and inner ears.
The inner ear is also called? And why?
because of its circular, maze‐like structure.
The part of the labyrinth that leads from the oval window is?
a bony, snail‐shaped structure called the cochlea.
The cochlea contains what?
special auditory liquids called perilymph and endolymph through which vibrations travel.
What is the organ of Corti?
a sensitive auditory receptor area present in the cochlea.
What happens in the organ of Corti?
tiny hair cells receive vibrations from the auditory liquids and relay the sound waves to auditory nerve fibers, which end in the auditory center of the cerebral cortex, where these impulses are interpreted and “heard”.
Why is the ear an important organ?
an important organ of equilibrium (balance), as well as an organ for hearing.
The vestibule connects what to what?
connects the cochlea (for hearing) to three semicircular canals for balance.
The semicircular canals contain what?
contain a fluid, endolymph, as well as sensitive hair cells. In an intricate manner, the fluid and hair cells fluctuate in response to the movement of the head.
This sets up impulses in nerve fibers that lead to the brain.
Messages are then sent to muscles in all parts of the body to ensure that equilibrium is maintained.
Channel that leads from the pinna to the eardrum
Waxy substance‐secreted by the external ear; also called ear wax
Snal‐shaped, spirally wound tube in the inner ear; contains hearing‐ sensitive receptor cells
Fluid within the labyrinth of the inner ear
Auricle; flap of the ear
Membrane between the outer and the middle ear; also called the eardrum
Hearing; the sense of hearing
Ear (see also ot/o)
Eardrum, tympanic membrane
Inflammation of the outer ear
Inflammation of the middle ear