Eye and Ear Histology LOs Flashcards
differentiate between the cornea, the limbus, and the sclera
cornea: clear
limbus: transition
sclera: white part of eye
list the 5 layers of the cornea, moving anterior to posterior
- corneal/anterior epithelium: stratified squamous non-cornified; much thicker than posterior epi
- anterior limiting membrane: basement membrane to corneal epi
- corneal stroma: thickest; type I collaged fibers arranged in layers intermixed with amorphous ground substance, avascular
- posterior limiting membrane/Decsemet’s membrane: basement membrane to posterior epithelium
- posterior epithelium: very low simple cuboidal epithelium, also called endothelium by opthamologists even though is avascular; much thinner than corneal epi
what type of CT proper makes up the sclera?
dense irregular connective tissue that varies in thickness around the globe
differentiate between the choroid, the ciliary body, and the iris
all part of middle layer of eye, called the uvea/vascular tunic
choroid: posterior surface of eye, contains the tapetum lucidum and the choriocapillary layer
differentiate between a choroid with a tapetum and a choroid without a tapetum
with no tapetum, vascular layer/stroma of choroid connects right to choriocapillary layer (ex. pigs)
with a tapetum, this layer is in between vascular layer/stroma and choriopcapillary layer
pigmented layer cannot be pigmented on top of a tapeteum; will have nonpigmented regions in a choroid with a tapetum
differentiate between a cellular (carnivore) and a fibrous (herbivore) tapetum
cellular: tapetal cells (fibrocytes) are arranged like stacked bricks
fibrous: thick, dense collagen fibers and fibrocytes
what portion of the visual retina does the choriocapillary layer supply?
nourishes the pigmented epithelium of the retina (the pigmented epithelium then nourishes the rods and cones)
choriocapillary layer: layer of capillaries immediately adjacent to the pigmented epithelium of the retina
differentiate between the flat and folded part of the ciliary body
flat part: pars plana
folded part: pars plicata, folds are called ciliary processes
differentiate between ciliary processes and zonular fibers
ciliary processes are folds of the ciliary body, they are connected to the lens by elastic zonular fibers (stretched between capsule of lens and BM of inner ciliary epithelium); originate from ciliary body between bases of ciliary processes
list the 2 major functions of the ciliary body
- play a role in accomodation
- produce aqueous humor
differentiate between the inner and outer layers of the ciliary epithelium
inner non pigemented layer and outer pigmented layer; arranged face to face with a basement membrane on each side
list the flow of aqueous humor between the ciliary epithelium and the trabecular meshwork of the iridocorneal angle
- aqueous humor is secreted into posterior compartment (behind lens where vitreous body is located) AND into the anterior compartment (in front of the lens)
- the anterior compartment is subdivided into the posterior chamber (between lens and iris) and the anterior chamber (between iris and cornea)
- the aqueous fluid is pumped into the posterior chamber, flows through the pupil into the anterior chamber, and exits through the trabecular meshwork at the iridiocorneal angle; it is then drained by the scleral venous sinus (canal of Schlemm)
what type of muscle is the ciliary muscle? if this muscle contracts, what happens to the lens and how does this affect vision?
ciliary muscle: smooth muscle
when these muscle fibers contract, the ciliary body rounds up, releasing tension on the zonular fibers and the lens thickens/becomes rounder, allowing the animal to focus on a close object (accomodation, parasympathetic innervation)
differentiate between the pupillary dilator muscle and the pupillary sphincter muscle
pupillary sphincter muscle: is arranged circumferentially around the free border or the iris in round pupils (canines and pigs), or the fibers cross laterally and medially in oval pupils (horses and ruminants), or fibers cross dorsally and ventrally in animals with slitlike pupils (felines); contraction decreases the diameter of the pupil and this muscle has parasympathetic innervation
pupillary dilator muscle: a myoepithelium because the anterior epithelial layer is partially differentiated into cells with contractile properties; radially oriented fibers along outer peripheral border; contraction increases the diameter of the pupil and this muscle has sympathetic innervation
what type of muscle are the sphincter muscles?
both are smooth muscle
what happens to the pupil when the dilator muscle contracts?
this muscle is longitudinally oriented and radially arranged around the pupil, so it increases the diameter (widens the aperture) when it contracts
what happens to the pupil when the sphincter muscle contracts?
this muscle is circumferentially arranged around the pupil so it decreases the diameter (narrows the aperture) of the pupil when it contracts
differentiate between the lens capsule, the lens epithelium, and the lens fibers
capsule: thickened basement membrane
epithelium: confined to anterior (cuboidal cells) and equatorial (elongated cells) surfaces of the lens
lens fibers: elongated lens epithelial cells, U-shaped; at equator of lens; fibers are added to the lens throughout the life of the animal
which part of the ANS innervates the sphincters?
autonomic
differentiate between the visual retina (retina) and the nonvisual retina (ciliary epithelium and iridial epithelium)
retina: 2 layers
1. pigmented epithelium: pigment quenches light photons, but this layer is NOT pigmented where it overlays a tapetum so that light photons can be reflected off the tapetum back onto phororeceptor cells
2. photoreceptor layer: the first neurons of the visual pathway! contains rods (low light ad night vision) and cones (bright light and color vision)
nonvisual retina:
the ora serrata is the junction between which portions of the neuroepithelial tunic?
visual and nonvisual retina
the inner and outer plexiform layers are where the 3 basic neurons of the visual pathway synapse; which two neurons synapse at the outer plexiform layer? which two neurons of the visual pathway synapse at the inner plexiform layer?
rods and cone cells synapse with bipolar and horizontal cells at the outer plexiform layer
bipolar neurons synapse with ganglion cells and amarcrine cells at the inner plexiform layers
the axons of which specific neurons join together and exit the eye at where (the blind spot), pass through the sclera, and form what nerve?
axonal processes of ganglionic cells (3rd neuron in visual pathway) come together to form optic nerve which gather at the posterior medial pole of the globe (optic disc)
optic disc = blind spot
list the 2 types of photoreceptor cells in the retina and indicate which of these is most abundant in the retina of the domestic species
cones and rods; rods predominate in domestic species
list the 3 subdivisions of the bony labyrinth
- semicircular canals
- vestibule
- cochlea
list the 3 subdivisions of the membranous labyrinth
- semicircular ducts: housed within semicircular canals
- utricle and saccule: housed within vestibule
- cochlear duct: housed within cochlea
list the sensory epithelial housed within each subdivision of the membranous labyrinth and the basic functions of each
- semicircular ducts contain a christa ampullaris that detects ANGULAR acceleration and deceleration
- each utricle and saccule contain a macula (macula of utricle and macula of saccule) that provide awareness of static equilibrium based upon detection of head’s orientation in space and detection of LINEAR acceleration and deceleration
- each cochlear ducts contains a spiral organ (organ of Corti) with the 3 subdivisions of scala vestibuli, scala media/cochlear duct, and scala tympani that detect sound vibrations
