S 1.2 Eyeball - pt.3 - C

Question 1

• It is the innermost coat of the eyeball.
• It is soft, translucent and pinkish red in color in fresh unbleached state.
• It consists of two parts: posterior three-fourth and anterior one-fourth

Answer 1

Inner Photosensitive Coat / Retina

Question 2

Inner Photosensitive Coat / Retina: Which part?
This is sensitive to light and is called the optic part of retina, which extends from the optic disc to a scalloped margin behind the ciliary body, the ora serrata
- (iridial part of retina) - double layer of epithelial cells

Answer 2

Posterior three-fourth

Question 3

Inner Photosensitive Coat / Retina: Which part?
This is nonsensitive to light and it lines the ciliary body (ciliary part of retina)

Answer 3

Anterior one-fourth

Question 4

Inner Photosensitive Coat / Retina:
The retina has an outer surface next to the highly vascular _________ and an inner surface in contact with the vitreous body. A highly ordered, multilayered structure, it is about ____ mm thick. From outside to inside, 10 distinct layers are usually seen in histologic sections.

Answer 4

choroid; 0.5

Question 5

Inner Photosensitive Coat / Retina:
10 distinct layers usually seen in histologic sections

Answer 5

1) The retinal pigment epithelium consists of one layer of melanin-rich cuboidal cells. Separated from the choroid by Bruch’s basement membrane, they are between the choroid and outer tips of photoreceptors.
2) A layer of rods and cones, arranged in parallel, is a prominent, fibrillar layer that comprises the outer photoreceptor segments.
3) An external limiting membrane is the line formed by junctional complexes between photoreceptors and supportive (Müller) cells.
4) An outer nuclear layer marks the middle nucleated parts of rods and cones, which are arranged in palisade manner.
5) The outer plexiform layer, a lightly stained zone, represents synaptic areas between photoreceptors and dendrites of bipolar cells.
6) An inner nuclear layer contains mostly cell bodies of bipolar cells, other associated neurons, and nuclei of Müller cells.
7) An inner plexiform layer is a relatively thick synaptic region, mostly between bipolar cells and ganglion cells, that also holds amacrine cell processes spreading laterally as interconnecting neurons.
8) The ganglion cell layer contains cell bodies of multipolar ganglion cells. Their dendrites branch in the inner plexiform layer, and their axons enter the next layer.
9) The nerve fiber layer comprises ganglion cell axons, about 1 million in each retina, that course radially toward the optic nerve.
10) An internal limiting membrane, the thin basal lamina of Müller cells, marks the boundary between neural retina and vitreous body.

Question 6

Inner Photosensitive Coat / Retina:
The visual axis of the eyeball passes through a depression in the retina called________ ________

Answer 6

fovea centralis

Question 7

Inner Photosensitive Coat / Retina:
- This is surrounded by an oval yellow pigmented area called macula lutea.
- About 4 mm medial to fovea centralis the retina shows a round pale pink area called optic disc or optic papilla.
- It is the area through which optic nerve leaves the retina, pierced by central vessels of retina, and considered to be the blind spot of retina as here photoreceptors are absent.

Answer 7

Fovea

Question 8

Inner Photosensitive Coat / Retina: Fovea:
This is surrounded by an oval yellow pigmented area called ____________ __________.

Answer 8

macula lutea