Eye and Ear Flashcards
Eye (8)
- eyeball or globe
- orbit
- eyelids
- conjunctiva
- lacrimal apparatus
- ocular muscles
- optic nerve
- vessels
Canine eye types (4)
Almond
Full, round, globular
Triangular
Oval
Also called “globe” or “bulbus oculi”
Eyeball
Eyeball is formed by three concentric coats:
◦ fibrous tunic – outer layer
◦ vascular tunic – middle layer
◦ nervous tunic – inner layer
Fibrous tunic is divided into: (2)
-sclera (opaque portion)
-cornea (transparent portion)
the main refractive element in the eye’s optical system
transmits over 90% of the incident light at visible wavelengths.
Cornea
*Cornea
transparency is achieved because, at the nanoscopic level, the _______ ________ ________ within the lamellae have a small, uniform diameter and are positioned with respect to each other with a high degree of lateral order.
corneal collagen fibrils
Layers of cornea (5)
Epithelium
Bowman’s layer
Stroma
Descemet’s layer
Endothelium
*Layer of the cornea
non-keratinized; replaced every 7 days
Epithelium
*Layer of the cornea
acellular, not regeneratable
Bowman’s layer
*Layer of the cornea
90% of corneal thickness; regeneratable
Stroma
*Layer of the cornea
produces by endothelium; basement membrane
Descemet’s layer
*Layer of the cornea
single layer of hexagonal cells; indivisible
Endothelium
the white part of the eye; constitutes the rest of the globe
Sclera
Function of the sclera (3)
Protects the intraocular contents from trauma and mechanical displacement.
Preserve the shape of the eyeball.
Provide a rigid insertion for extraocular
muscles.
also called uvea or uveal tract
Vascular tunic
inflammation of vascular tunic is called
uveitis
*Vascular tunic
consist of (from posterior to anterior) (3)
a. choroid
b. ciliary body
c. iris
also known as the choroidea or choroid coat,
the vascular layer of the eye, containing connective tissue
lies between the retina and the sclera
Choroid
4 Layers of choroid
Haller’s layer
Sattler’s layer
Choriocapillaris
Bruch’s membrane
*Layer of the choroid
outermost layer of the choroid consisting of larger diameter blood vessels
Haller’s layer
*Layer of the choroid
layer of medium diameter blood vessels
Sattler’s layer
*Layer of the choroid
layer of capillaries
Choriocapillaris
*Layer of the choroid
(syn: Lamina basalis, Complexus basalis, Lamina vitra) - innermost layer of the choroid
Bruch’s membrane
*Mechanism
_______ helps the choroid limit uncontrolled reflection within the eye that would potentially result in the perception of confusing images
Melanin
*Mechanism
In many animals, however, the partial absence of melanin contributes to superior night vision. In these animals, melanin is absent from a section of the choroid and within that section a layer of highly reflective tissue, the ______ _______, helps to collect light by reflecting it in a controlled manner.
tapetum lucidum
*Mechanism
The uncontrolled reflection of light from dark choroid produces the photographic _______ effect on photos, whereas the controlled reflection of light from the tapetum lucidum produces ________
red-eye effect
eyeshine
structure in the eye that releases a transparent liquid (called the aqueous humor) within the eye.
Ciliary body
a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupil and thus the amount of light reaching the retina.
The color of the this gives the eye its color.
iris
the innermost tunic of the eye
it is also called the nervous coat or retina
it is therefore connected to the brain by the optic nerve
Nervous tunic
3 distinct areas of the nervous tunic:
a. pars iridica retinae
b. pars ciliaris retinae
c. pars optical retinae
comprise the nonvisual or blind retina (2)
-Pars iridica retinae
-Pars ciliaris retinae
is the visual retina or the only part that is photosensitive
*Pars optica retinae
*The photoreceptors of the retina are the rods and cones: rods function at _____ and cones function at ________. Presence of rods plus tapetum indicates a better vision in reduced illumination.
night
daylight
a transparent, biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina.
Changes shape so that it can focus on objects at various distances. This adjustment is known as accommodation.
Lens
is bounded by the cornea anteriorly and the iris posteriorly
anterior chamber
is bounded anteriorly by the posterior face of the iris and posteriorly by the anterior lens capsule; it is smaller than the anterior chamber
posterior chamber
*Anterior and posterior chambers of the eye
these 2 chambers are filled with _______ _____; should be clear and colorless; it is maintained at an __________ _______ of approximately 15 – 30 mm of Hg in the dog; this pressure is essential to maintain the normal shape and firmness of the
aqueous humor
intraocular pressure
the largest of the 3 chambers of the eye
the vitreous body occupies this
the vitreous body is a soft, clear gel which conforms to the shape of the cavity it occupies
it maintains the shape of the eyeball
Vitreous chamber
the cavity or socket of the skull in which the eye and its appendages are situated.
can refer to the bony socket
Orbit
*Foramina present in the medial wall of the orbit
where optic nerve and internal ophthalmic artery pass as they leave the cranial cavity
optic canal
*Foramina present in the medial wall of the orbit
gives passage to the oculomotor, trochle, abducent and ophthalmic nerves; the retractor bulbi muscles originates here
orbital fissure
*Foramina present in the medial wall of the orbit
transmits the external ethmoidal artery and nerve
2 ethmoidal foramina
*Foramina present in the medial wall of the orbit
continued rostrally as the lacrimal canal which contains the nasolacrimal duct
Fossa for lacrimal sac
5 Foramina present in the medial wall of the orbit
optic canal
orbital fissure
rostal alar foramen
2 ethmoidal foramina
Fossa for lacrimal sac
a thin fold of skin that covers and protects the eye.
The levator palpebrae superioris muscle retracts this to “open” the eye. This can be either voluntarily or involuntarily (blinking)
Eyelid
lines the inside of the eyelids and covers the sclera (white part of the eye)
helps lubricate the eye by producing mucus and tears, although a smaller volume of tears than the lacrimal gland
It also contributes to immune surveillance
and helps to prevent the entrance of microbes into the eye.
Conjunctiva
a group of organs concerned with the production and drainage of tears
a protective device that helps keep the eye moist and free of dust and other irritating particles.
Lacrimal apparatus
*Lacrimal apparatus
contributes to the production of tear film, the precorneal tear film is essential to the normal transparent state of the cornea; lacrimal fluid flows across the cornea, aided by blinking.
Lacrimal gland or tear gland
*Lacrimal apparatus
includes the lacrimal puncta (dorsal and ventral), lacrimal caniculi, lacrimal sac and nasolacrimal duct
Nasolacrimal Duct System
*Lacrimal apparatus
located on the inner surface of the upper and lower lid margins; they are the oval openings of the lacrimal canaliculi; the lacrimal canaliculi enter the lacrimal sac which is the dilated origin of the nasolacrimal duct; the nasolacrimal duct passes from the lacrimal sac thru the lacrimal canal.
Lacrimal Puncta
a dog “leads with its ears”
An organ of hearing and balance
Ear
shape of the ear is characteristic of the _____, and there are many types of outer ears
breed
Parts of the ear (3)
external ear (pinna and external auditory meatus)
middle ear
internal (inner) ear
*External ear
◦ ear flap or auricle
◦ highly mobile and can be controlled independently
◦ a funnel-like plate of cartilage that receives air vibrations and transmits them via the ear canal to the eardrum (tympanic membrane)
Pinnae
*External ear
◦ Presents a cutaneous lining which includes stratified squamous epithelium, rich in sebaceous and tubular glands and hairs
◦ Sebaceous and tubular glands both secrete and cerumen or ear wax
External Auditory Meatus
Consists of the tympanic cavity, tympanic membrane (ear drum) and the 3 auditory ossicles (malleus, incus, stapes)
It is connected to the pharynx by way of the auditory tube or the Eustachian tube
Middle ear
Tympanic membrane contains (4)
a. auditory ossicles
b. chorda tympani (tympanic nerve)
c. ossicular muscles
d. auditory tube
has 3 small bones which transmit air vibrations from the tympanic membrane across the cavity of the middle ear to the inner ear
Auditory ossicles
*Auditory ossicles
The most lateral and the largest is the _______, the most medial is the ______ and is the smallest bone in the body, between the malleus and the stapes is the _____
malleus
stapes
incus
Nerve of Jacobson
contains both sensory and secretory fibers
leaves the facial nerve to join the lingual nerve
Chorda tymphani or Tympanic membrane
*Ossicular muscles
which acts to draw the malleus medially, tensing the tympanic membrane
Tensor tympani
*Ossicular muscles
the smallest skeletal muscle in the body; it moves the rostral end of the base of the stapes caudolaterally
Stapedius muscle
also known as the eustachian tube or pharyngotympanic tube
a tube that links the nasopharynx to the middle ear
Auditory tube
4 largest muscle asso. the Eustachian tube
- Levator veli palatini (innervated by the vagus nerve)
- Salpingopharyngeus (innervated by the vagus nerve)
- Tensor tympani (innervated by the mandibular nerve of CN V)
- Tensor veli palatini (innervated by the mandibular nerve of CN V)
It is housed in a bony labyrinth in the petrous portion of the temporal bone. The bony labyrinth contains the membranous labyrinth with its sensory organs responsible for hearing and balance.
Inner ear
*Inner ear
Bony inner ear can be divided into three parts:
a. the rostral part is the cochlea
b. caudal part consists of the three semicircular canals
c. bony vestibule
what serve as the body’s balance organ
semicircular canals and vestibule
which serves as the body’s microphone, converting sound pressure impulses from the outer ear into electrical impulses which are passed on to the brain via the auditory nerve.
cochlea
The cochlear duct contains the end organ of hearing, the organ of _____
Corti
Ciliary body contains the _______ _______, which changes the shape of the lens when your eyes focus on something. This process is called _____________
ciliary muscle
accommodation
*Iris
In optical terms, the _____ is the eye’s ________ and the iris is the diaphragm that serves as the ________ ____
pupil
aperture
aperture stop
