Special senses eye and ear Flashcards
What are the three layers of the eye?
Corneoscleral coat (outer fibrous layer, inc. cornea, sclera)
Uvea (middle layer, inc. iris, ciliary board, choroid)
Retina (inner layer, inc. inner neutral retina, outer pigment epithelium)
Outline the cornea
Anterior surface of eye
Transparent
Richest nerve supply
Refracts light
Usually avascular
What are the five layers of the cornea?
Corneal epithelium
Bowman’s membrane
Corneal Stroma
Descemet’s membrane
Corneal epithelium
What are the 3 ill-defined layers of the sclera?
External episcleral layer
Middle layer substania propria (tenon’s capsule)
Inner suprachoroidal lamia
Outline the choroid
Functions as blood supply and absorbs scattered light
Choriocapillary layer
Brunch’s membrane (lamina vitrea)
Outline the iris
Forms a contractile diaphragm in front of lens
Pupil id central aperture
Outline the ciliary body
Ciliary muscle (smooth, contract to reduce tension of zonular fibres, relax to increase)
Ciliary processes (vascular, to produce and anchor zonular fibres, secretes aqueous humor and a part of the blood-aqueous barrier)
Where is the corneoscleral limbus (junction) located?
Between cornea and sclera, transition zone
Outline the vitreous bodysuit
Posterior eye segment, jelly-like and transparent
Homogenous gel
Maintains shape of eye and helps keep retina in place
Hyalocytes
Composition can change with age
Outline the retina
Neutral retina (retina proper) = inner layer of optic cup, non photosensitive region anterior to ora serrata, photosensitive region posterior to ora serrata
Retinal pigment epithelium = outer layer of optic cup
Where in the eye are the highest densities of rods and cones?
Fovea centralis
What are the functions of the retinal pigment epithelium?
Absorption of light
Major component in blood-retina barrier
Active in visual pigment pathways
Vitamin A metabolism
What are 3 special regions of the retina?
Optic disc = site where optic nerve emerges from retina (blind spot)
Macula lutea = center of posterior retina
Fovea centralis = small depression in centre of macula lutea, area of highest visual activity
Outline the lens
A biconvex structure
Avascular
Held in place by zonular fibres
Contains: lens capsule, subcapsular epithelium, and lens fibres
Outline the conjunctiva
Stratified epithelium with goblet cells
Lines the inside of eyelid and visible part of sclera
Secretes fluid to lubricate eye
Outline the glands of the eyelid
Meibomian glands = lubricates, delays tear drying
Glands of Zeiss = associated with eyelashes
Glands of Moll = Sweat glands at lid margins
Outline the three divisions of the ear
External ear (auricle, external acoustic meatus)
Middle ear (tympanic membrane, auditory ossicles, auditory tube)
Internal ear (bony labyrinth, membrous labyrinth)
Outline both labyrinths of the internal ear
Bony = 3 connected spaces (semicircular canals, vestibule, cochlea), perilymph
Membranous = communicating sacs and ducts suspended within bony labyrinth (cochlear labyrinth with cochlear duct, vestibular labyrinth with semicircular ducts), endolymph
Outline the crista ampullaris
Sensory receptor for angular movement of head
Outline macula of utricle
Sensors of gravity and linear acceleration
What are the 3 components of the cochlea?
Scala media
Scala vestibuli
Scala tympani
Outline the Spiral organ of Corti
Sensor of sound vibrations
Inner (single row) and outer hair cells (variable rows)
How do we perceive sound?
Mechanical vibrations converted to fluid at oval window
Fluid vibrations cause displacement of basilar membrane
Different frequencies cause maximum displacement of certain segments along length
Shearing effect between membrane and tectorial membrane cause deflection of stereocilia
Activation of MET channels
Generation of nerve impulse
Sent to brain vis cochlear nerve
