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PDI 521- Exam 1- Eyes and Ears
Terms in this set (74)
Identify the location of the anterior and posterior chambers of the eye
Anterior chamber- between the cornea and iris
Posterior chamber- between the iris and the lens
Identify the posterior segment and its components
Posterior to the posterior chamber of the anterior segment. Posterior to the lens, contains vitreous body
Identify/describe the following anatomic structure: eyelid and conjunctiva
Outer protective lid and the pink part of the inside of the eyelid
Identify/describe the following anatomic structure: cornea
Smooth, glassy outer surface where ulcers are common
Identify/describe the following anatomic structure: limbus
junction between the sclera and cornea
Identify/describe the following anatomic structure: sclera
White part of the exterior eyeball, has vessels and nerves
Identify/describe the following anatomic structure: iris
pigmented portion of the eye, muscular, constricts the pupil
Identify/describe the following anatomic structure: pupil
black "hole" in the middle of the iris, where light passes through
Identify/describe the following anatomic structure: iridocorneal angle
between the iris and the cornea, where aqueous humor drains
Identify/describe the following anatomic structure: ciliary body
extends from the iris to the choroid and the retina, produces aqueous humor
Identify/describe the following anatomic structure: zonula fibers
arise at the ciliary body and extend to the lens
Identify/describe the following anatomic structure: lens
dividing boundary for the anterior and posterior segments of the eye
Identify/describe the following anatomic structure: retina
transmits photons to the brain as a neural signal via the optic nerve
Identify/describe the following anatomic structure: tapetum lucidum
posterior portion of the eye, reflects light back onto the retina to increase vision in low light
Identify/describe the following anatomic structure: optic disc
posterior portion of the eye leading to the optic nerve, fundus
Identify/describe the following anatomic structure: optic nerve
nerve fibers of ganglion layer join and exit the globe; surrounded by meninges connecting to the brain
List the three concentric layers of the globe
Fibrous (outer) layer= choroid
Vascular (middle) layer= uvea
Neural (inner) layer
Components of the fibrous layer of the eye
Sclera, cornea, limbus
Components of the vascular layer or uvea of the eye
iris, ciliary body, choroid
Components of the neural layer of the eye
Sensory portion of the retina, pigment epithelium, optic nerve and disc
What is the purpose of the fibrous layer of the eye? What type of tissue is it comprised of?
The fibrous layer is the "supporting coat" of the eye, its function is to keep fluid in the eye and maintain ocular pressure.
It is made up of dense collagenous CT
What are some components of the sclera? What type of tissue is it made of?
Dense irregular CT
+/- cartilage or bone in some species
Many blood vessels and nerves
List the components/layers of the cornea
What type of epithelium makes of the corneal epithelium?
5-7 layers of non-keratinized stratified squamous
What type of tissue makes up the Bowman's membrane? What species is it NOT prominent in?
dense collagen, acellular
NOT prominent in dogs or cats
What are some histologic features of the corneal stroma?
Linearly arranged stromal fibers that allow the passage of light
What is the significance of Descemet's membrane?
will increase in thickness over time
decreases flexibility of the cornea with age
What is the function of the corneal endothelium?
-avascular and transparent
-what you see "through"
-allows air to pass through the eye
What is the significance of the limbus? What type of cells are found here?
-transition between the sclera and the cornea
-important part of the drainage apparatus
-stem cells of the corneal epithelium are found here
List components of the uvea
Iris, ciliary body, choroid
Describe the muscles found within the iris and their function
Dilator pupillae= radially arranged (dilates)
Sphincter pupillae= circular muscle within pupillary 1/3 of the iris (constricts)
Name example(s) of species that have the following types of muscle in their iris:
None: fish, amphibians, some reptiles
Describe the features and functions of the ciliary body. What type of tissue is it comprised of?
-extends from the iris to the choroid and retina
-produces aqueous humor
-involved in accomodation
-composed of loose CT, smooth muscle, and epithelium
Describe the features and functions of the ciliary epithelium
Bilayer with tight junctions
Name and describe the two parts/processes of the ciliary epithelium
Pars plicata- ciliary processes; ridge-like projections
Pars plana- flat region
What is the ora serrata?
the junction between the ciliary body and the retina
What is the flow of aqueous within the eye?
Ciliary body>posterior chamber>pupil>anterior chamber> ciliary cleft> trabecular meshwork> +/- collecting ducts> scleral venous plexus
What is the ciliary cleft? How is it developed?
-large spaces crossed by pectinate ligaments
-develops by attrition of regression of mesenchyme to form flow holes
What are the two parts of the trabecular meshwork?
TM is a fine meshwork with both a corneoscleral and a uveoscleral part
Describe the features and function of the choroid
-Lies between the retina and the sclera
-highly vascular, supplies blood to the outer retina
- contains numerous melanocytes to absorb stray photons (highly pigmented)
What is the function of the tapetum lucidum?
responsible for eye shine; enhances night vision by allowing light to reflect and pass through the retina twice
What are the two types of tapetum lucidum?
Retinal and choroidal
Give an example of an animal with a retinal tapetum
What are the three types of choroidal tapetum lucuidum? Give an example of a species with each.
-Cellular: mammalian carnivores, rodents
-Fibrous: ruminants, horses
What species do NOT have a tapetum lucidum?
pigs, rabbits, humans, birds (excluding whippoorwill)
Describe the histologic features of retinal pigment epithelium.
Simple cuboidal cells-- pigmented in the inferior fundus and non-pigmented in the superior (tapetal) fundus
Separated from choroid by a basement membrane (Bruch's membrane)
Describe the function of the retinal pigment epithelium
-Pigmented portion absorbs photons passing through the retina
- forms a blood-retina barrier via tight junctions (limits flow from choroid to the neural retina)
-phagocytizes and recycles shed components of photoreceptors
What are the layers of the neural retina?
inner limiting membrane>nerve fiber layer>ganglion cell layer> inner plexiform layer> inner nuclear layer> outer plexiform layer> outer nuclear layer> outer limiting membrane> rods & cones> retinal pigment epithelium> choroid
What is the centralis retinae? Where is it located? What makes it unique? What species is it well developed in?
-region of most acute vision
-temporal to the optic disc (lateral)
-increased number of cones
-1:1 ratio of ganglion cells to photoreceptors
-well developed in primates and birds (fovea)
What is the general function of Mueller cells?
supporting glial cells of the retina
Describe the histologic appearance of the optic nerve and the optic disc
-nerve fibers of the ganglion layer join and exit the globe
-depression at the head is visualized on fundoscopy called the optic disc
At the sclera, the optic nerve is supported by a meshwork of collagenous trabeculae called what?
scleral lamina cribrosa
What is the function of the lens?
It is organize to be transparent and focuses incoming light onto the retina. It is avascular but metabolically active.
What suspends the lens in the eye?
zonular fibers that connect it to the ciliary body
What are the components of the lens?
-Anterior subcapsular epithelium
-Capsule (thick anterior that grows over the life of the animal and thin posterior)
-Lens fibers from the epithelium
What are general histologic features of the lens?
-lens fibers from the epithelial cells elongate, lose their nuclei, and gain crystalline proteins
-lens fibers are linearly arranged
-few cells with oblong purple nuclei in the subcapsular epithelium and forming lens fibers
Describe the composition of the vitreous body
gel-like substance that fills the posterior compartment
99% water and 1% hyaluronic acid, glycoproteins, collagen, salts, sugars
What is the purpose of the vitreous body?
-holds the retina against the choroid
-maintains the shape of the globe and keeps the retina pushed against the sclera
Describe the function of the eyelid and tear film
important in mechanical protection, limiting light intake, lubrication and immune response
What are some species differences in the eyelid?
third eyelid= nictitans
spectacles in snakes
absent in amphibians, teleosts and some reptiles
Describe the three layers of the tear film, where they come from and their purpose.
Lipid layer- meibomian gland (holds fluid in the eye)
Aqueous layer- lacrimal gland
Mucous layer- goblet cells (adheres tear film to the cornea)
What is the function of the middle ear?
to convert sound waves into mechanical vibrations that are transmitted to the inner ear
What separates the middle from the external ear?
the tympanic membrane (ear drum)
What connects the middle ear to the nasopharynx?
the Eustachian (auditory) tube
What is the function of the Eustachian tube?
to equalize pressure of the middle ear with atmospheric pressure
it is closed at rest and open when swallowing
What is another name for the gutteral pouch?
the diverticulum (part of the middle ear that contains air)
What are the components of the middle ear?
auditory (Eustachian) tube
+/- gutteral pouch
oval and round window
List the three bones of the middle ear and their general function
Malleus, incus, stapes
-attach to the tympanic membrane on one side and the oval window on the other side
-vibrations sent through the external and middle ear are transmitted to the inner ear
Describe the components that form the tympanic membrane and their histologic features
-skin of the external acoustic meatus (stratified squamous epithelium)
-connective tissue core with many collagen fibers
-mucosa of the tympanic cavity/middle ear (simple squamous/cuboidal epithelium)
Describe the functional vs structural divisions of the inner ear
Functional: vestibular and auditory apparatuses
Structural: bony and membranous labyrinths
List the components of the vestibular apparatus
semicircular ducts, saccule, utricle
Describe the function of the cristae ampullaris and the maculae
Cristae ampullaris is located in each semicircular duct-- it senses the angular acceleration and position of the head
maculae is present in both the utricle and saccule-- it senses gravity and linear acceleration
What is the function of the organ of corti?
detects sound vibrations and generates signal; basilar membrane transmits sound waves
Where is the organ of corti found?
in the cochlear duct (scala media)
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