Retina

Question 1

Where is the retina located between?

Answer 1

• the retina is located between the choroid and macula

Question 2

Where does the retina extend too and from?

Answer 2

• retina extends from the edge of the optic disc to the ora serrata

Question 3

What is the retina continuous with?

Answer 3

• retina continuous with epithelial layers of the ciliary body

Question 4

What does the retina share its embryonic origin with?

Answer 4

• shares its embryonic origin with the epithelial layers of the ciliary body

Question 5

Where is the pigmented outer layer of the retina derived from?

Answer 5

• outer layer of the optic disc

Question 6

Where is the neural retina derived from?

Answer 6

• inner layer of the optic cup

Question 7

What is the pigmented layer adherent to?

Answer 7

• the choroid

Question 8

Where is the pigmented layer adherent?

Answer 8

• throughout whole choroid

Question 9

What is the neural retina adherent to?

Answer 9

• attached to the pigmented epithelium
• choroid around only in periphery ring around the disc and the ora serrata

Question 10

What’s the appearance of the neural retina?

Answer 10

• a thin transparent membrane

Question 11

What are the layers of the retina?

Answer 11

1) retinal pigment epithelial layer
2) photoreceptor layer
3) external limiting membrane
4) outer nuclear layer
5) outer plexiform layer
6) inner nuclear layer
7) inner plexiform layer
8) ganglion cell layer
9) nerve fiber layer
10) internal limiting membrane

Question 12

What is the outermost retinal layer?

Answer 12

• outermost layer is the retinal pigment epithelium(RPE)

Question 13

What is the thickness of the RPE?

Answer 13

• RPE is one cell thick

Question 14

What’s the shape of the RPE cells?

Answer 14

• Hexagonal

Question 15

How do the RPE cells change shape?

Answer 15

• columnar shaped in the area of the posterior pole
• longer, narrower and more densely pigmented in the macula area
• cells become larger and more cuboidal near ora serrata

Question 16

What does the RPE transition to?

Answer 16

• ciliary epithelium

Question 17

Where does the RPE transition to the ciliary epithelium?

Answer 17

• near ora serrata

Question 18

What are melanosomes?

Answer 18

• pigment granules

Question 19

Where are the melanosomes located in the RPE cells?

Answer 19

• extend from the apical area into the middle portion of the cell

Question 20

What is the RPE cells nucleus obscured by?

Answer 20

• melanosomes

Question 21

What can give the fundus a blotchy appearance when viewed with ophthalmoscope?

Answer 21

• pigment density varies across the retina

Question 22

Where is melanin most dense in the retina?

Answer 22

• macula
• equator

Question 23

What are other pigmented bodies in the retina?

Answer 23

• lipofuscin granules

Question 24

What are lipofuscin granules?

Answer 24

• contain degradation products of phagocytosis, increase with age

Question 25

What does the apical portion of the RPE consist of?

Answer 25

• microvilli

Question 26

Where do the microvilli of the RPE extend to?

Answer 26

• layer of photoreceptors
• envelops the outer segment tips

Question 27

What joins the RPE cells near their apices?

Answer 27

• terminal bars consisting of zonula occludens and zonula adheres

Question 28

What do gap junctions between the RPE cells allow for?

Answer 28

• electrical coupling
• provides a low resistance pathway for the passage of ions and metabolites

Question 29

What passive forces are involved in the maintenance of the close approximation between the photoreceptor cell layer and the RPE?

Answer 29

• intraocular pressure
• osmotic pressure
• fluid transport across RPE
• presence of vitreous

Question 30

What is the interphotoreceptor matrix(IPM)?

Answer 30

• organized honeycomb structure that occupies the extracellular space between the RPE cells and photoreceptors

Question 31

What is the IPM composed of?

Answer 31

• proteins and glycosaminoglycans

Question 32

How do the constituents of the IPM domains around rods differ to those around the cones?

Answer 32

• those surrounding the cones are described as a matrix sheath

Question 33

What are the IPM constituents bound to?

Answer 33

• the epithelial cells and photoreceptor cells

Question 34

What are some of the functions of the IPM?

Answer 34

• exchange of metabolites
• interactions between the two layers
• orientating the photoreceptor outer segments for optimal light capture

Question 35

What are the six parts the rods and cones are composed of?

Answer 35

1) outer segment
2) cilium(connecting stalk)
3) inner segment
4) outer fiber
5) the cell body
6) the inner fiber

Question 36

What is the structure of the outer segment?

Answer 36

• stack of membranous discs enclosed by plasmalemma of the cell
• each disc a flattened sac with narrow intradisc space
• visual pigment molecules located within disc membrane

Question 37

What is the cilium?

Answer 37

• a connecting stalk
• extends from innermost disc, joining the the outer segment with the inner segment, acting as a conduit between them
• modified cilium made up of nine pairs of tubules, but central pair is missing

Question 38

What does the inner segment contain?

Answer 38

• the cellular structures

Question 39

What are the two parts the inner segment can be divided into and what do they contain?

Answer 39

ellipsoid - contains mitochondria
Myoid - contains others organelles

Question 40

How are the axis of the inner and outer segments oriented?

Answer 40

• oriented towards pupil of the eye

Question 41

Where does the outer fiber extend from?

Answer 41

• inner segment to the cell body

Question 42

What does the cell body contain?

Answer 42

• the nucleus

Question 43

What is the inner fiber?

Answer 43

• an axonal process containing microtubules
• runs inward from the cell body