Histology of the Eye and Ear

Question 1

What are tarsal (Meibomian) glands?

Answer 1

special sebaceous glands

Question 2

What is a stye?

Answer 2

infection of the sebaceous glands of the eyelashes

Question 3

What type of glands are lacrimal glands

Answer 3

tubuloacinar serous

approx 12 ducts

Question 4

What type of cells make up the palpebral and bulbar cunjuctiva?

Answer 4

stratified colunar with goblet cells

Question 5

What type of embryo tissue gives rise to the different parts of the retina?

Answer 5

neuroecto (inner) –> neural retina

surface ecto –> pigmented retina

Question 6

what embryo tissue forms the eyelid and outer cornea?

Answer 6

ectoderm overlying lens vesicle

Question 7

What are the 3 basic layers of the eye?

Answer 7

corneoscleral = outer fibrous coat
vascular coat = choroid, stroma
retina = inner coat, epi of ciliary body and iris, retina

Question 8

What makes up the vitreous body?

Answer 8

space btw lens and neural retina

vitreous humor: 99% water w/ proteins and hyaluronan

Question 9

What is the main refractor of the eye?

Answer 9

the cornea

Question 10

What are the 5 layers of the cornea?

Answer 10

epithelium = strat squamous
bowman’s membrane (ant basement membrane)
corneal stroma: layers arranged at right angles, avascular
descemet’s membrane (post BM): very thick
corneal endothelium: simple squa

Question 11

Where are the stem cells for the cornea located?

Answer 11

in the limbus region of the epithelium

Question 12

What are the 2 layers of choroid?

Answer 12

inner vascular layer

Bruch’s membrane (thick amorphous ECM)

Question 13

What are ciliary processes?

Answer 13

bits of ciliary body that secrete aqueous humor; anchor zonular fibers that make suspensory L of the lens

Question 14

What are the parts of the iris?

Answer 14

pupil in center
dilator: radial band
sphinctor: circular band
posterior pigmented epithelium

Question 15

What is the limbus apparatus?

Answer 15

trabecular network and canal of Schlemm that absorbs excess aqueous humor

Question 16

What are the 3 parts of the lens?

Answer 16

capsule: flexible, elastic eCM (no cells)
subcapsilar lens epithelium: cells on periphery proliferate and migrate centrally to make mature lens fiber cells
lens fibers: filled w/ crystallins and lose all organelles

Question 17

When is the central lens nucleus established?

Answer 17

during embryonic development

Question 18

What is accommodation?

Answer 18

tension from ciliary body transmitted by zonular fibers to change lens shape

Question 19

What is presbyopia?

Answer 19

loss of lens elasticity with age

Question 20

What cells make up the retinal pigmented layer?

Answer 20

simple cuboidal epi on Bruch’s membrane of the choroid
blood-neural retinal barrier; absorbs stray light
phagocytoses disc shed form rods and cones

Question 21

What isomerizes retinal?

Answer 21

retinal pigmented layer

trans retinal –> 11-cis retinal –> back to photoreceptors

Question 22

are there lymphatics in the neural retina?

Answer 22

no

Question 23

What are the retinal layers from superficial to deep?

Answer 23

1. RPE
2. Rod and cone ends
3. Outer limiting membrane (zona adherens attaching to apical ends of muller cells)
4. Outer nuclear layer
5. Outer plexiform layer (processes of rods/cones and processes of horizontal, amacrine, and bipolar cells connecting)
6. inner nuclear layer (horizontal, amacrine, and bipolar cells)
7. inner plexiform layer: process of ganglion, amacrine, bipolar, horzontal cells
8. Ganglion layer
9. Layer of optic N fibers
   10: Inner limiting membrane

Question 24

Which retinal cell is more sensitive?

Answer 24

rods

Question 25

What are the 3 classes of cone cells?

Answer 25

blue
green
red

Question 26

What are the visual pigments and where are they?

Answer 26

rods have rhodopsin

cones have iodopsin

Question 27

What is the general structure of rods and cones?

Answer 27

outer segment: photosensitive part = PM discs –> connected to inner segment via modified cilium
connecting stalk
inner segment: major organelles

Question 28

What are photosensitive discs?

Answer 28

PM parts of the outer segment of rods and cones - shed during normal functioning
phagocytosed by RPE cells

Question 29

What is the fovea centralis?

Answer 29

highest concentration of cones
avascular
surrounded by macula lutea

Question 30

What is retinoblastoma?

Answer 30

AD disorder
mutation in Rb gene = tumor suppressor (G1–>S)
malignant tumor or retina that dev in children under 5
see leukocoria (white pupil)
strabismus = misalignment of eyes

Question 31

What makes up the organ of corti?

Answer 31

3 rows of outer hair cells

1 row of inner hair cells

Question 32

What is the path of sound waves?

Answer 32

stapes moves oval window –> wave in perilymph –> distorts vestibular membrane –> wave in endolymph of scala media –> moves basilar membrane –> perilymph in scala tympani moves and wave exits via round window

Question 33

How does the ampulla sense rotational velocity?

Answer 33

in semicircular canals
endolymph filled
end of canals have ampullaris w/ cupulla
hair cells attached to cupulla
fluid motion w/ rotation –> moves cupulla –> nerve innervating senses movement

Question 34

What does the vesibule sense and how does it do it?

Answer 34

saccule and utricle have macula = cluster of hair cells w/ stereocilia w/ overlying otolithic membrane
membrane covered w/ otoconia crystals –> move with head movement –> sense gravitational position

Question 35

What are the 3s in audio-vestibular system?

Answer 35

3 parts: outer, middle and inner
3 sensory systems: audition, rotational velocity, gravity/linear velocity
3 bones
3 turns in the cochlea
3 semicircular canals
3 nerves: vestibular, acoustic, facial
2 maculae, can detect acceleration in 3 dimensions