Eye Flashcards Preview

Cell Biology 2 > Eye > Flashcards

Flashcards in Eye Deck (42):
1

What are the three layers of the wall of the eye?

Corneo-scleral - outermost layer that provides protection/light focusing
Choroid/Uvea - vascular layer
Retina - light sensing and technically part of the brain

2

Blood ocular barrier exists in two parts (kind of an arbitrary distinction)

Blood - retinal barrier (RPE and retinal capillaries)
Blood - aqueous barrier (ciliary epithelium and iris capillaries)

3

What are the five layers of the cornea? What types of nerves are there in the cornea?

Outer epithelium
Bowman's membrane
Stroma
Descemet's membrane
Inner endothelium

free nerve endings to sense foreign objects in contact/trigger tearing response

4

what type of epithelium does the cornea have?

strat. squamous

5

What does Bowman's membrane do? What unique character does it have?

protects the cornea from infection
collagen fibrils formed by the stroma
does not regenerate when damaged

6

What types of cells do you find in the stroma?

keratocytes - modified fibroblasts

7

what does Descemet's membrane do?

presents a barrier to macromolecule diffusion into the cornea

8

what does the corneal endothelium do?

maintains the stroma's water content

9

name three vision defects related to the cornea

myopia (nearsightedness)
hyperopia (farsightedness)
astigmatism - eccentric shaped cornea that misfocuses light`

10

what are four procedures that can be used to repair the cornea?

RK - radial keratotomy: central incision (not done anymore)
AK - astigmatic keratotomy: incision at the steepest part of the cornea (not done anymore)
PRK - photorefractive keratotomy - uses an eximer laser (UV based) to remove epithelium
LASIK - laser keratomileusis - peeling off the epithelium and bowman's membrane and then carving out the stroma

11

what is the limbus? what does it do?

the junction between the cornea and the sclera; houses the stem cells for the cornea; vascularized in the stroma

12

what marks the conjunctiva from the limbus and the sclera?

presence of goblet cells; note that this is continuous with the skin of the eyelid

13

why is the cornea clear?

presumably due to the presence of lumican and keratocan that arrange the collagen fibrils into their highly ordered orthagonal arrangement

14

what are the layers of the lens?

Capsule
single layer of cuboidal epithelium (anterior only)
fibrous synctium

15

what is special about the lens fiber synctium?

the cells are anucleated

16

what supports the lens?

zonules (of Zinn) that extend from the epithelium of the ciliary processes (composed of fibrillin)

17

what two conditions represent pathology of the lens?

presbyopia - lack of elasticity of the lens that comes with age - makes it difficult to focus on objects up close
cataracts - when the lens turns opaque

18

what are the two/three functions of the retina?

Reception/transmission of image data
prevention of backscattering of light

19

at the point of "attachment" of the choroid to the retina, what do you find in abundance?

melanocytes and capillaries (with fenestrated epithelium)

20

what are the layers of the retina?

RPE
photoreceptors
outer limiting membrane
outer nuclear layer
outer plexiform layer
inner nuclear layer
inner plexiform layer
ganglion cell layer
nerve fiber layer

21

what does the RPE do?

prevents backscattering of light
collects photoreceptor "debris"
maintains the blood-retinal barrier (tight junctions)

22

what forms the outer limiting membrane?

tight junctions between Muller cells and photoreceptor neurons; probably prevents flow of macromolecules into the inner layer of the retina

23

outer (external) nuclear layer

nuclei of the photoreceptor cells

24

Outer plexiform layer

contains axons of photoreceptors and processes of interneurons (amacrine, horizontal, bipolar)

25

inner nuclear layer

cell bodies of the interneurons

26

inner plexiform layer

dendrites of ganglions and interneurons meet here

27

ganglion cell layer

cell bodies of ganglions
IMPORTANTLY: also contains circadian rhythm light sensing cells

28

nerve fiber layer

axons of ganglion cells; microvasculature of the retina in this layer; also have the extensive tight junctions for the blood-retinal barrier

29

stuff to know about rods! are they found in the fovea?

low light (scotopic) sensing receptors that use VItamin A derived retinal and rhodopsin to sense light from dark; GPCR's
FOVEA -NO!!!!

30

cones?

color sensing (photopic) receptors that come in three flavors (RGB) that use iodopsin to sense their color; high concentration in the fovea

31

wtf is the macula lutea?

yellow boundary around the optic disc; full of xanthophyll

32

are there blood vessels in the fovea?

NOPE!@#

33

what does the posterior epithelium of the iris do?

blocks light (melanin)

34

anterior pigment myoepithelial layer

also has the melanin; helps to form the dilator pupillae muscles

35

is the stroma of the iris highly or lowly vascularized?

highly; also has melanocytes that determine eye color

36

ciliary process epithelium has how many layers? what's so special here?

2 layers; their apical ends face each other and the basement membrane of the inner layer (this is the luminal layer) attaches to zonules of Zinn; inner layer is non-pigmented, outer layer is pigmented

37

stroma of the ciliary body/process vascularization special features?

highly vascularized and continuous tight junctions

38

what else does the inner layer of the ciliary body epithelium do?

anchors the zonules and produces aqueous humor (what do you mean, what ELSE does it do?) (also has tight junctions for blood-ocular barrier, phew, that's a lot of work)

39

what are the pressures inside the ciliary body and the aqueous chambers?

13 mmHg and 20 mmHg

40

so what do these lazy pigmented cells do?

block light

41

what's the flow of the aqueous humor?

inner epithelial layer of the ciliary body/process -> posterior chamber -> anterior chamber -> trabecular meshwork -> canal of schlemm -> episcleral veins

42

what do you call it when the pressures are out of whack and aqueous humor builds up in the eye?

glaucoma, man