HISTO: Eye & Ear Flashcards
What are the three eyeball layers?
Outer fibrous layer - Corneoscleral
Middle vascular coat - Uvea
Inner layer - Retina
Light rays are refracted to reach the ____ cells of the retina
Photoreceptor
What 4 components alter path of the light rays?
- cornea
- aqueous humor
- lens
- vitreous body
The anterior part of the corneoscleral coat of the eye:
The cornea
Watery fluid that fills the anterior chamber (space between cornea and the iris) and the posterior chamber:
Aqueous humor
A transparent, crystalline, biconcave structure suspended from the inner surface of the ciliary body by a ring of radially oriented fibers, the zonule of Zinn:
Lens
Transparent gel substance that fills the vitreous chamber (space between the posterior surface of the lens and the neural retina):
Vitreous body
What are the parts of the Cornea?
External corneal epithelium
Bowman’s membrane
Stroma
Descement’s membrane
Corneal endothelium
DNA in corneal epithelial cells is
protected from UV light damage by:
Nuclear ferritin
Randomly oriented collagen fibrils (Type-I) Not separable from substantia propria:
Bowman’s membrane
Derived from mesenchyme from mesoderm. Continuous with developing sclera:
Stroma - substancia propia
No blood vessels!!
Derived from neural crest cells. Thick basal lamina produced by endothelium (collagen Type IV and VIII):
Hint (cornea)
Descement’s membrane and corneal endothelium
Regenerates
During an inflammatory response involving the cornea, large numbers of neutrophilic leukocytes and lymphocytes migrate from blood vessels of the _________ and penetrate the stromal lamellae.
Corneoscleral limbus
Posterior part of the fibrous layer. Dense irregular connective tissue:
Sclera
the Canal of Schlemm contains:
Trabecular meshwork
that merges to form for the outflow of the aqueous humor.
A clinical condition resulting from increased intraocular pressure over a sustained period of time.
• It can be caused by excessive secretion of aqueous humor or impedance of the drainage of aqueous humor
Glaucoma - causing the retinal nerve fiber layer to atrophy and ganglion cells to die
A characteristic finding for glaucoma:
enlargement of the optic cup
First choroidal blood vessels appear in what week?
15th
Thin brown vascular layer next to inner surface of sclera:
Choroid
What is choroids function?
Light absorption and blood supply
What are the layers of the choroid?
Vessel layer - loose ct
Choriocapillar layer
Bruch’s membrane - glassy, refractile layer using collagen and elastin fibrils and pigmented epithelium of retina
Ciliary body function?
Accommodation for near vision, secretion of aqueous humor
What muscle is included in the ciliary body?
Muller’s muscle (of accomodation)
How do contraction of these muscles accommodates for near vision?
Smooth muscle, circular fibers (Muller’s)
reduces tension of suspensory ligaments→
more convex→Contraction for near vision
Fingerlike projections towards lens:
Ciliary processes
Secretes aqueous humor:
Ciliary epithelium
Pigmented portion of ciliary epithelium can develop from:
Develops from outer layer of optic cup
Non-pigmented portion of ciliary epithelium can develop from:
Develops from inner layer of optic cup.
Form tight junctions!!! Blood-aqueous barrier
What are the parts of the iris?
- Stroma
- Sphincter of pupil
- Pupil dilator
- Pigment epithelium
Spongy layer of iris. Contains fibroblasts and melanocytes, (number affects iris color)
Stroma
Derived from neuroectoderm of optic cup. Reduces pupil diameter. It is innervated by parasympathetic nerves:
Sphincter of pupil
Opens pupil. Radially-arranged myoepithelial cells. It is under sympathetic nerve control, fibers from the superior cervical ganglion:
Pupil dilator
Increase of the pupil diameter is called:
mydriasis
Derived from the 2 layers of optic cup. Continuous with epithelium of ciliary body, retinal pigment epithelium and neural retina:
Pigment epithelium
What are the parts of the lens?
- Lens capsule
- Subcapsular lens epithelium
- Primary lens fibers
- Secondary lens fibers
• Thick basal lamina, produced by anterior lens epithelium.
• Collagen Type IV and proteoglycans
Lens capsule
• Forms from anterior wall of lens vesicle.
• Cuboidal epithelium
Subcapsular lens epithelium
• Formed by elongated columnar
cells of posterior wall of lens
vesicle. They fill the lens cavity.
• Present from birth
Primary lens fibers
• Elongated cells at rim of lens
(equatorial zone) Hexagonal
prisms filled with crystallins
• Added throughout adulthood
Secondary lens fibers
Changes with age: Loss of transparency
Cataract
It acts as a “shock absorber” that protects the fragile retina during rapid eye movement and helps to maintain the shape of the eye:
Vitreous body
The vitreous body is made up of?
99% water (humor), proteins, hyaluronan, glycoproteins, collagen fibrils.
Parts of the retina:
Inner layer of optic cup
Outer layer of optic cup
Forms retinal pigment epithelium:
Outer layer of optic cup
Forms neural retina, that includes photoreceptors and all the neurons in the retina:
Inner optic cup
Separation of the ___ can cause retinal detachment
Intraretinal space: Is the original cavity of optic cup. It reduces but never disappears.
Rods pigment:
rhopdopsin
Cones pigment:
iodopsin
The outer segments of the cones in the center of the fovea is called:
Foveola
Highest density of cones cone density increases almost 200-fold
Region of highest visual acuity
Fovea centralis
The phagocytosis of the photoreceptor tips, tight junctions, absorbs light and prevents reflection and glare are functions of
RPE (retinal pigmented epithelium)
Physical Separation of photoreceptors from RPE cells are the basis for:
Retinal detachment, loss of visual
The most common cause of blindness people over age 55:
ARMD - age related macular degeneration
perihperal vision unaffected
External ear is composed of:
Auricle and external acoustic meatus
The middle ear is composed of:
tympanic cavity, auditory ossicles, tympanic membrane, and auditory tube
The internal ear is composed of:
The bony labyrinth (semicircular canals, vestibule, and cochlea: blue) and the membranous labyrinth (not visible)
A complex system of interconnected cavities and canals in the petrous part of the temporal bone.
Bony labyrinth
Lies within the bony labyrinth and consists of a complex system of small sacs and tubules
Membranous labyrinth
The bony labyrinth consists of three connected spaces within the temporal bone:
● semicircular canals
● vestibule
● cochlea.
The central space that contains the utricle and saccule of the membranous labyrinth
Vestibule
3 tubes within the temporal bone that lie at right angles to each other: superior, horizontal, posterior:
Semicircular canals
At the end of each canal is a dilation called:
ampulla
Is a bony coiled canal, connected to the vestibule. It makes approximately 2.75 turns around a central core of bone called the modiolus:
Cochlea
These two openings are located at the base of the cochlear canal:
A thin membrane covers the round window, and the stapes is positioned within the oval window.
The bony labyrinth is filled with:
Perilymph: low K+ concentration and a high Na+ concentration
The membranous labyrinth is filled with:
Endolymph: high K+ concentration and a low Na+ concentration
The cochlear labyrinth contains the ______ within the cochlea and communicates with the saccule
cochlear duct
The vestibular labyrinth contains:
- Three semicircular ducts that are continuous with the utricle
- The utricle and the saccule, which are contained in the vestibule
- Endolymphatic duct and endolymphatic sac
Epithelial mechanoreceptors:
Hair cells
Which hair type has a base is enclosed in a chalice- like afferent nerve ending, kinocilium (9+2) and stereocilia?
Hair type I
Hair cell type I actin is crosslinked by:
fimbrin and espin
Which hair cell type is cylindrical and possesses several nerve terminals at its base for both afferent and efferent nerve fibers?
Hair cell type II
Hair cells communicate with afferent nerve fibers through ____ synapses, a specialized type of chemical synapse.
ribbon synapse
What are the 6 sensory cells of the membranous labyrinth?
2 maculae - head position and lineal movement
3 cristae ampullaris - angular acceletarion
spiral organ of Corti - sound receptor
Sensory region located in the ampulla
Type I hair cells, Type II hair cells and supporting cells
Crista ampullaris
Cone-shaped gelatinous protein– polysaccharide mass, known as the _____, is attached to the hair cells of each crista.
Cupula - projects into the lumen and is surrounded by endolymph
Responds to angular movements of the head
Crista ampullaris
Sensors of gravity and linear acceleration:
The maculae of the saccule and utricle
- consist of type i and ii hair cells
The gelatinous polysaccharide material that overlies the maculae is called the:
otolithic membrane
crystalline bodies of calcium carbonate and protein:
otoliths
what does meineires syndrome cause:
Excess endolymph fluid in the endolymphatic duct
Causes severe vertigo, nausea and tinnitus (ringing in the ears) and also hearing loss.
Cochlear duct is made up of:
Scala media - cochlear duct
Scala vestibuli and scala tympani
Basilar membrane
Space within cochlear duct filled with endolymph. Contains the organ of Corti:
Scala media
Specialized perilymphatic spaces surrounding cochlear duct:
Scala vestibuli and tympani
Separates scala tympani from scala media. Supports organ of Corti:
Basilar membrane
Separates Scala vestibuli and Scala media:
Reissner’s membrane =
(vestibular membrane) roof of cochlear duct.
extensive tight junctions
the sensor of sound vibrations
The spiral organ of Corti
Produces endolymph:
stria vascularis
Single row along basilar membrane. 50-70 stereocilia:
inner hair cells
Cylindrical shape. 3-5 rows along basilar membrane. 100-300 stereocilia arranged in ”V” shape:
outer hair cells
Gelatinous, proteoglycans Overlies stereocilia of hair
cells:
tectorial membrane
support hair cells:
Inner and outer phalangeal cells
Steps of sound production:
Vibration of basilar membrane →
Moves hair cells of organ of Corti stereocilia→
Depolarization, transmitter release of bipolar neurons (spiral ganglion)
Dysfunctions of the Vestibular System examples:
Viral infections and acoustic neuromas, BPPV, Ménière’s disease
dysfunctions to the auditory system examples:
Sensorineural hearing impairment
Sensorineural hearing loss age-related
what is presbycusis
high-frequency hearing loss
Benign paroxysmal positional vertigo (BPPV) causes
otoconia become detached from the macula of the utricle and lodge in one of the three cristae ampullaris
initially episodes of dizziness and tinnitus (ringing in the ears) and later development of low-frequency hearing loss
Meneire disease
Viral infections and acoustic neuromas can cause:
sensation of rotation without equilibrium (dizziness, vertigo)
Sensorineural hearing impairment - 90% of hearing loss occurs where?
after injury to the auditory sensory hair cells within the internal ear, cochlear division of cranial nerve VIII, nerve pathways in the CNS, or auditory cortex
