6.3 Eye Histology

Question 1

What are the 5 layers of the cornea?

Answer 1

1. The outer stratified non keretanized squamous epithelial layer (EP)
2. Bowman’s membrane (BM) specialized layer
3. Substantia propria (SP)
4. Descemet’s membrane (DM)
5. Endothelium

Question 2

[5 layers of cornea]
Outer ___________________ epithelial layer (EP)
• Originated from ____________________
• remarkable regenerative capacity (turnover 7 days)
• Extremely sensitive to touch – elicits blink reflex_

Answer 2

stratified non-keratinised squamous;

surface ectoderm;

Question 3

[5 layers of cornea]
Bowman’s membrane (BM) – specialized layer of corneal stroma that support the _________________
• Anterior basement membrane, homogenous layer
• Barrier to infections and confers some strength to cornea

Answer 3

basal lamina of epithelium

Question 4

[5 layers of cornea]
Substantia propria (SP) – the bulk of cornea consisting of dense collagen tissue forming as thin lamella
• Thickest layer, made of __________________
• Underlying ECM rich in _______________

Answer 4

slender and flattened fibroblasts with interspersed collagen fibres;

corneal proteoglycans (sulphated GAGs)

Question 5

[5 layers of cornea]
Descemet’s membrane (DM) – thick basement membrane that support the inner most layer
• Posterior basement membrane
• Lies between the corneal proper substance (stroma) and the endothelial layer of the cornea, contains collagen type ___________
• Interwoven meshwork of ________________

Answer 5

IV and VIII;

fibres and pores

Question 6

[5 layers of cornea]
Endothelium (EN) – ____________ endothelial layer
• Highly active, prevents excessive dehydration
• Virtually all cellular metabolic exchanges take place here
• Site of _______________

Answer 6

flattened;

endocytic action and cell transport

Question 7

what are examples of photoreceptor cells?

Answer 7

retinal rods and cones

Question 8

what are examples of Conducting neurons (conducts the impulse perceived by the photoreceptor cells into the other layers) cells?

Answer 8

bipolar neurons and ganglionic cells

Question 9

what are examples of association neurons and others (supporting the conductive pathway)?

Answer 9

horizontal, centrifugal, interplexiform and amacrine neurons

Question 10

what are examples of supporting (neuroglial) cells

Answer 10

Muller’s cells, microglial cells and astrocytes

Question 11

What are the 10 layers of the retina?

Answer 11

1) retinal pigment epithelium
2) photoreceptor layer: rods and cones
3) outer limiting membrane
4) outer nuclear layer
5) outer plexiform layer
6) inner nuclear layer
7) inner plexiform layer
8) ganglion cell layer
9) layer of optic nerve fibers
10) inner limiting membrane

Question 12

[The Ten Layers Of Retina]

Layer 1 – retinal pigment epithelium: single layer of cuboidal cells rest on ______________ of choroid layer (b) intimately connected with __________________
• absorbs light passing through neural retina
• forms major component of ________________
• participates in restoring photosensitivity

Answer 12

Bruch’s membrane;

neural part of retina;

blood retinal barrier

Question 13

[The Ten Layers Of Retina]
Layer 2 – Photoreceptor layer – contains the processes of the photoreceptor cells (_______________)
• Appear as _______________ in light microscopy due to their side by side (palisade) arrangement
• Rods – more sensitive to bright light, receptors of low light intensity, contains ________________
• Cones – less sensitive to low light, more sensitive to RGB spectrum, contains ____________

Answer 13

rods and cones;

vertical striations;

rhodopsin pigment;

iodopsin

Question 14

[The Ten Layers Of Retina]

Layer 3 – Outer limiting membrane – the apical boundary of _______________

Answer 14

Muller’s cells

Question 15

[The Ten Layers Of Retina]

Layer 4 – Outer nuclear layer – contains the _________________

Answer 15

cell bodies of rods and cones

Question 16

[The Ten Layers Of Retina]

Layer 5 – Outer plexiform layer – contains the process and synaptic connections between the _______________ and _____________ present in the inner nuclear layer

Answer 16

photoreceptor cells;

integrating neurons

Question 17

[The Ten Layers Of Retina]

Layer 6 – Inner nuclear layer – contains the cell bodies of _____, __________, ________, _______________

Answer 17

horizontal cells, amacrine cells, bipolar cells and Muller cells

Question 18

[The Ten Layers Of Retina]

Layer 7 – Inner plexiform layer – contains the process and synaptic connections between the cells of ________________ and dendrites of ________________

Answer 18

inner nuclear layer;

ganglionic cell layer (layer 8)

Question 19

[The Ten Layers Of Retina]

Layer 8 – Ganglionic cell layer – contains the cell bodies of ___________________

Answer 19

optic tract neurons (retinal ganglion cells)

Question 20

[The Ten Layers Of Retina]

Layer 9 – Layer of optic nerve fibres - contains processes of ganglion cells that lead from the _______________

Answer 20

retina to the brain

Question 21

[The Ten Layers Of Retina]

Layer 10 – Inner limiting membrane – demarcates the innermost aspect of retina from the ______________

Answer 21

vitreous body (VB)

Question 22

Rod photoreceptors are long slender bipolar cells, more sensitive to ___________, receptors of ______________, contains rhodopsin pigment ;

• Outer segment – _____________ shape, contains stack of ______________ which incorporate the pigment rhodopsin
• Inner segment – contains a prominent ___________________

The outer and inner segments are connected by thin cytoplasm containing ___________________

Answer 22

bright light;

low light intensity;

cylindrical;

flattened membranous discs;

Golgi apparatus and many mitochondria ;

microtubules

Question 23

Cone photoreceptors – less sensitive to low light, more sensitive to ___________, contains ____________

• Outer segment – long conical structure, contains stack of _______________, spaces between the discs are continuous with extracellular environment . Incorporates iodopsin, receptive to RGB colours
• Inner segment – prominent _________________
• Outer and inner segments are continuous with each other

Answer 23

RGB spectrum;

iodopsin;

continuous flattened membranous discs;

Golgi apparatus and many mitochondria

Question 24

What are bipolar cells responsible for?

• Responsible for transmitting impulse to _________________

Answer 24

retinal ganglion cells (conducting cells)

Question 25

What are retinal ganglion cells responsible for?
• Final receivers and transmitters of initial stimulus
• Axons eventually form the __________ and project to higher brain centres

Answer 25

optic nerve

Question 26

What are Muller cells responsible for?
• Supporting cells of retina, maintain __________________
• Fill most of extracellular space – extend from layers 3 to 10, with cell bodies in ____________

Answer 26

structural and functional stability of retinal cells;

layer 6

Question 27

What are Amacrine cells responsible for?
• Interneurons, synaptically active in the ____________________
• Serve to integrate, modulate and interpose the visual images presented to ganglionic cells

Answer 27

inner plexiform layer

Question 28

What are horizontal cells responsible for?

• Function to modulate communication between _________________

Answer 28

photoreceptors and bipolar cells

Question 29

Lens – ___________________ structure

• elastic bioconvex structure – transparent and amorphous, modified epithelial cells are derived from _____________
• During development, the early lens vesicle hosts a ____________, which is gradually occupied by the elongation of _________________
• Cells undergo maturation to form the lens fibres
• The anucleate lens fibres stretch between anterior and posterior poles of lens, packed with ____________
• -> Cell membranes of adjacent fibres are fused, leaving little intervening extracellular space
• -> Enveloped by thick epithelial basement membrane forming the lens capsule made up of _________
• Damage to the lens fibres result in opacity, causing cataract
• -> Occur due to ageing, trauma to the lens, inflammatory diseases within the eye or in response to some metabolic diseases

Answer 29

ectoderm;

central cavity;

posterior cells;

crystallin proteins;

cuboidal epithelium