Veterinary Science: Anatomy and Physiology; Section 11 Eye & Ear
Two major functions of the ear
hearing and balance.
Process of hearing
sound vibrations are transformed into a nervous impulse & transmitted to the brain by the auditory nerve.
cranial nerve VIII.
Process of balance
nerve endings in the ear sense changes in position of the head.
Three parts of the ear
external, middle, inner.
funnel-shaped, made of skin and cartilage. narrow down to ear canal.
Ear canal is common for...
ear mites, and infections.
ear drum. separates external ear from middle ear.
middle ear. hollow chamber.
connects the pharynx to the middle ear.
Bones of the ear and function
hammer, anvil, stirrup. vibrate when noises heard.
Inner ear found in the...
petrous temporal bone.
Two parts of the inner ear and functions of each
Cochlear (hearing), vestibular (balance).
Snail-shaped, filled with fluid.
Organs of corti
Structures on the cochlea projecting outward, has cilia.
Deafness can be due to...
sound wave conduction problems, inflammation, injury, obstruction or nerve problem.
Equilibrium controlled in...
three semicircular canals oriented in three planes (transverse, horizontal, vertical), that contain fluid with small crystals.
Problems with the three semicircular canals
Vertigo (Dizziness), motion sickness, nystagmus.
Rapid back-and-forth eye movement.
External layer of eye
Fibrous coat containing the cornea and sclera.
Clear, anterior part of eye. Has nerves.
White posterior part of eye; dense and opaque. Has blood vessels and nerves. Muscle attach to it.
Area where cornea and sclera meet.
Cranial Nerve II connected to back of eye.
Pigmented portion of eye. Ring of muscle that opens or closes to control amount of light let in.
"Pupillary opening." Opening of the iris. Round in most species, elliptical in cats and snakes.
Behind iris. Biconvex, transparent, and elastic.
Behind the lens, filled with vitreous humor, gelatinous.
In front of the lens, watery.
In front of iris.
Glaucoma, and use what to measure
Aqueous humor made quicker than it can exit eye. Increased pressure. Use tonometer to measure pressure.
Muscle that contracts to make lens thinner, and relaxes to make lens thicker.
Bending of light to focus on retina. Distance = thinner, Closer = thicker.
Used to see, 10 nervous tissue layers thick, picks up light and transmits it to brain down optic nerve, contains pigment.
Reflective part of retina, eye glows.
Where nerves in the retina join. Where optic nerve links eye to brain.
Back of the eye where retina and optic nerve can be seen.
Used to examine eye.
Photoreceptors in eye
Rods and cones.
Cells very sensitive to light.
Cells used for detail and color perception.
Palpebra and function
Eyelids. Keep eye from drying out, make lubrication in glands in corner of eye.
Mucous membrane lining of eye.
Corner of the eye. Medial and lateral.
Cherry eye and common in...
Tear in gland attached to third eyelid, sticks out. Common in cocker spaniels.
Tear glands found in dorso-lateral eye.
Function of tears
Wash away debris, lubricate, keep cornea moist.
"Puncta." Two small openings that drain fluid at the medial canthus.
Inflammation/infection of the conjunctiva. Common in animals with URTI.
Bones in the ear.