Ear and Eye Histology Flashcards
external ear consists of
auricle (pinna)
external auditory meatus
tympanic membrane
middle ear consists of
tympanic cavity (connects to pharynx by auditory tube)
bordered by tympanic membrane and oval window
ossicle: malleus, incus, stapes
inner ear consists of
oval window and round window
bony labyrinth
membranous labyrinth
connects to CN VIII
- vestibulo- (balance)/ cochlear (hearing)
separates external ear from middle ear
tympanic membrane
layers of tympanic membrane
epidermis (outer; ectoderm)
fibrous tissue (middle layer; mesoderm)
simple squamous/cuboidal epithelium (inner layer; endoderm)
what is cerumen an where is it produced
ear wax
skin with ceruminous glands in EAM
cavity in petrous portion of temporal bone; connects to pharynx by auditory tube
middle ear
2 tiny muscles in middle ear
tensor tympani and stapedius
what do ossicles do?
transmit sound vibrations from tympanic membrane to oval window of inner ear
magnifies vibrations
tensor tympani attaches to _____
stapedius attaches to _____
malleus
stapes
bony case in petrous portion of temporal bone filled with perilymph fluid
bony labyrinth
fluid that fills bony labyrinth - between bony labyrinth and membranous labyrinth
perilymph fluid
3 parts of the bony labyrinth
Semicircular canals
vestibule
cochlea
3 loops at right angles to each other
contain semicircular ducts
sense rotational acceleration
semicircular canals
dilated area in inner ear joined by ampullae
contains oval and round windows
contains utricle and saccule that sense linear acceleration
vestibule
sense linear acceleration (2)
utricle and saccule
“snail-like” spiral of bony labyrinth
contains cochlear duct
cochlea
membranous and sensory labyrinth are suspended in bony labyrinth and fill with _____
endolymph fluid
membranous and sensory labyrinth connects (3)
semicircular ducts
utricle and saccule
cochlear duct
membranous/sensory labyrinth connects to which nerve?
vestibulocochlear (CN VIII)
utricle is a attached to _______ ducts
saccule is attached to _______ duct
semicircular
cochlear
utricle and saccule hooked together by ______ duct
endolymphatic
contains neuroepithelium with type I and type II hair cells
covered with otolithic membrane that contains otoliths
connects to vestibular portion of CN VIII
Maculae of utricle
contains cristae ampullares (neuroepithelial cells)
- type I and II hair cells - covered with cupula (a gelatinous cap)
Ampullae of semicircular ducts
hair cells with a rounded base, narrowing towards apical end
type I
hair cells that are more columnar, have a larger Golgi, and more cytoplasmic vesicles
type II
contains the organ of corti
cochlear duct
2 perilymph-filled tubes that connect at apex of cochlea:
_________ connected to oval window
_________ connected to round window
Scala vestibuli
Scala tympani
apex of cochlea; allows the scalae to communicate
Helicotrema
three membranes lining the organ of corti
Vestibular (Reissner’s) - roof
Basilar - floor
Tectorial - covers organ
specialized receptor for hearing that is composed of neuroepithelium with inner and outer stereocilia that synapse with axons of cochlear portion of CN VIII
organ of corti
Describe hearing
sound waves through external auditory meatus to tympanic membrane
tympanic membrane converts sound waves to mechanical energy
ossicles vibrate and amplify sound
stapes moves the oval window and initiates pressure waves in perilymph
pressure change travels to scala vestibuli –> helicotrema –> scala tympani
pressure change in scala tympani causes basilar membrane to vibrate organ of Corti, deflecting stereocilia, and generating impulses transmitted by CN VIII
pressure waves dissipate via round window
describe how we sense linear movements
displacement of endolymph moves otoliths, bending stereocilia of hair cells and generating impulses conducted by CN VIII
describe how we sense circular movements
displacement of endolymph moves cupula, bending stereocilia and generating impulses conducted by CN VIII
hearing loss from excess fluid accumulation in the endolymphatic duct
- other s/s: vertigo, tinnitus, n/v
Meniere’s disease
happens when something impedes conduction through middle ear
conductive deafness
results from disease process that interrupts transmission of nerve impulse
nerve deafness
three tunics/layers of the eye (outer to inner)
sclera and cornea - outer fibrous tunic
choroid, ciliary body, and iris - middle vascular tunic
retina, neuroepithelium on ciliary body - inner neural tunic
three chambers of the eye
anterior chamber - aqueous humor
posterior chamber - aqueous humor
vitreous chamber - vitreous body
white of the eye that gives shape
continuous with the cornea
tendons of extraocular muscles insert here
sclera
sclera is enveloped by ________ - a fascial sheath that covers optic nerve and most of eye
capsule of tenon
6 layers of the cornea (outer to inner)
non-keratinized ss epithelium (only 5-7 cells thick!)
Bowman’s membrane
corneal stroma
pre-descemet layer (Dua layer)
Descemet’s membrane
Corneal endothelium
90% of corneal thickness
composed of 200-250 type I collagen lamellae
relatively dehydrated, giving transparency
corneal stroma
basement membrane of cornea made by endothelium and fibroblasts
Descemet’s membrane
what does the pre-descemet layer probably do?
protect cornea from damage
3 pain components of vascular tunic
iris
ciliary body
choroid
two smooth muscles found in core of iris
dilator pupillae
sphincter pupillae
anterior surface is covered with
melanocytes
posterior surface of iris is covered with
pigmented epithelium
layer of loose fibrous tissue, melanocytes (which give it a black color), and vessels between retina and sclera
choroid
expansion of choroid that gives rise to the iris
contains vessels and smooth muscle (ciliary muscle) for accommodation of lens, and ciliary processes
ciliary body
produce aqueous humor and give rise to zonules (suspensory ligaments)
ciliary processes
converts photons of light to sensory nerve impulses
retina
yellow-pigmented zone of the retina
macula lutea
center of macula and point of highest visual acuity
fovea centralis
“blind spot” where retina attaches to optic nerve and no photoreceptor cells are
optic disk
10 layers of retina (deep to superficial)
“In New Generation It Is Only Ophthalmologists Examining Patient’s Retina”
inner limiting membrane nerve fiber layer ganglion neuron layer inner plexiform layer inner nuclear layer outer plexiform layer outer nuclear layer external limiting membrane photoreceptor layer retinal pigment epithelium
nerve fiber layer of retina contains
axons from ganglion neurons that connect to optic nerve
outer nuclear layer of retina contains
nuclei of photoreceptor cells
contain rhodopsin - for dim light vision
rods
contain iodopsin - for color, bright light vision; have better acuity
cones
inner limiting membrane of retina is touching the ____
retinal pigment epithelium is touching _____
vitreous body
choroid
site of retinal detachments
retinal pigment epithelium
transparent, light-focusing element of the eye
lens
describe lens fibers
anucleate cells fill with crystallins that continue to elongate throughout life
describe the vitreous body
acellular mass of gel that fills vitreous chamber
vitreous body is composed of (3)
water, collagen, and hyaluronic acid
what is nuclear sclerosis
the cloudiness, hardening, and yellowing of the central region of the lens
type of tissue that covers lens
simple cuboidal epithelium
3 glands of eyelids
Tarsal (Meibomian) glands
- sebaceous on free margin of eyelid
Glands of Moll
- modifies sweat glands open into eyelash follicle
Glands of Zeis
- modified sebaceous that open into eyelash follicle
CN II
optic nerve
optic nerve is derived from and contains
optic vesicle
ganglion cell axons
