Special senses eye and ear

Question 1

What are the three layers of the eye?

Answer 1

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)

Question 2

Outline the cornea

Answer 2

Anterior surface of eye
Transparent
Richest nerve supply
Refracts light
Usually avascular

Question 3

What are the five layers of the cornea?

Answer 3

Corneal epithelium
Bowman’s membrane
Corneal Stroma
Descemet’s membrane
Corneal epithelium

Question 4

What are the 3 ill-defined layers of the sclera?

Answer 4

External episcleral layer
Middle layer substania propria (tenon’s capsule)
Inner suprachoroidal lamia

Question 5

Outline the choroid

Answer 5

Functions as blood supply and absorbs scattered light

Choriocapillary layer
Brunch’s membrane (lamina vitrea)

Question 6

Outline the iris

Answer 6

Forms a contractile diaphragm in front of lens
Pupil id central aperture

Question 7

Outline the ciliary body

Answer 7

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)

Question 8

Where is the corneoscleral limbus (junction) located?

Answer 8

Between cornea and sclera, transition zone

Question 9

Outline the vitreous bodysuit

Answer 9

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

Question 10

Outline the retina

Answer 10

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

Question 11

Where in the eye are the highest densities of rods and cones?

Answer 11

Fovea centralis

Question 12

What are the functions of the retinal pigment epithelium?

Answer 12

Absorption of light
Major component in blood-retina barrier
Active in visual pigment pathways
Vitamin A metabolism

Question 13

What are 3 special regions of the retina?

Answer 13

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

Question 14

Outline the lens

Answer 14

A biconvex structure
Avascular
Held in place by zonular fibres
Contains: lens capsule, subcapsular epithelium, and lens fibres

Question 15

Outline the conjunctiva

Answer 15

Stratified epithelium with goblet cells
Lines the inside of eyelid and visible part of sclera
Secretes fluid to lubricate eye

Question 16

Outline the glands of the eyelid

Answer 16

Meibomian glands = lubricates, delays tear drying

Glands of Zeiss = associated with eyelashes

Glands of Moll = Sweat glands at lid margins

Question 17

Outline the three divisions of the ear

Answer 17

External ear (auricle, external acoustic meatus)
Middle ear (tympanic membrane, auditory ossicles, auditory tube)
Internal ear (bony labyrinth, membrous labyrinth)

Question 18

Outline both labyrinths of the internal ear

Answer 18

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

Question 19

Outline the crista ampullaris

Answer 19

Sensory receptor for angular movement of head

Question 20

Outline macula of utricle

Answer 20

Sensors of gravity and linear acceleration

Question 21

What are the 3 components of the cochlea?

Answer 21

Scala media
Scala vestibuli
Scala tympani

Question 22

Outline the Spiral organ of Corti

Answer 22

Sensor of sound vibrations
Inner (single row) and outer hair cells (variable rows)

Question 23

How do we perceive sound?

Answer 23

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