Visual Pathway Anatomy

Question 1

The 7 major parts of the Visual Pathway

Answer 1

1) Retina
2) Optic Nerve
3) Optic Chiasm
4) Optic Tract
5) Lateral Geniculate Nucleus
6) Optic Radiations
7) Striate Cortex (visual cortex)

Question 2

How many cells and synapses in the visual pathway? What are the cells?

Answer 2

5 cells, and 4 synapses (between the cells)
The 5 cells:
1) Recepetor cell in the retina (rod or cone)
2) Bipolar cell in the retina
3) ganglion cell in the retina
4) LGN neuron
5) Visual cortex neuron

Question 3

what structures are the axons of the ganglion cells?

Answer 3

optic nerve, optic chiasm, optic tract

Question 4

what structure is the axons of the LGN?

Answer 4

optic radiations

Question 5

how long is the optic nerve?

Answer 5

5-6 cm

Question 6

what are the sections of the optic nerve?

Answer 6

intraocular
intraorbital
intracanal (part that passes through optic canal)
intracranial (from the optic canal to the optic chiasm)

Question 7

what is the diameter of the optic nerve intraocularly and postlaminarly?

Answer 7

1.5 mm intraocularly, 3 mm postlaminarly

Question 8

what does the lamina cribrosa have to do with the visual pathway?

Answer 8

it is the network of scleral fibers through which the optic nerve fibers exit the globe

Question 9

describe the meningeal sheaths of the optic nerve

Answer 9

the optic nerve is sheathed in meningeal layers that correspond with, and are continuous with, the cerebral meningeal layers (dura, arachnoid, and pia)

Question 10

how is the intraocular ON bundled?

Answer 10

into fascicles by astrocyte sheaths

Question 11

how is the postlaminar ON bundled?

Answer 11

by an additional connective tissue sheath, and by oligodendrocyte myelination

Question 12

what is the intermediary tissue (of Kuhnt)?

Answer 12

the ring of glial tissue that separates the ON fibers from the retinal layers

Question 13

what is the border tissue (of Jacoby)?

Answer 13

a continuation of the the intermediary tissue of Kuhnt, which separates the ON fibers from the choroid

Question 14

what is the border tissue (of Elschnig)?

Answer 14

a ring of collagenous tissue that lies outside of the glial sheaths of the ON

Question 15

what is the clinical significance of the attachment of certain EOMs to the ON sheath? what is this condition called?

Answer 15

movement of the eyes may cause pain if the optic nerve is swollen (optic neuritis)

Question 16

the ON is inferior to the _________ and the _________.

Answer 16

olfactory tract, anterior cerebral artery

Question 17

the ON is lateral to the _________.

Answer 17

sphenoidal sinus

Question 18

the ON is _________ to the olfactory tract and anterior cerebral artery.

Answer 18

inferior

Question 19

which EOMs are attached to the ON sheath?

Answer 19

medial and superior recti

Question 20

the ON is _________ to the sphenoidal sinus.

Answer 20

lateral

Question 21

what supplies blood to the prelaminar and laminar ON?

Answer 21

unfenestrated peripapillary choroidal network

Question 22

what is the function of the glial tissue network of the prelaminar ON?

Answer 22

it provides structural support for the delicate nerve fibers

Question 23

what are the glial tissues of the prelaminar ON?

Answer 23

the intermediary tissue (of Kuhnt), the border tissue (of Jacoby), and the marginal/border tissue (of Elschnig)

Question 24

what is a fenestrated capillary? unfenestrated?

Answer 24

a fenestrated capillary is one with small pores that allows small molecules and some proteins to diffuse through; unfenstrated do not have these pores, and so limit what passes through

Question 25

what blood vessels supply the postlaminar portion of the ON?

Answer 25

opthalmic a.
central retinal a.
pial vessels

Question 26

what blood vessels supply the intracranial ON?

Answer 26

opthalmic a.
anterior cerebral a.
anterior communicating a.
internal carotid a.