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Lec 22- Optic Nerve

The optic nerve is a collection of what that exits the eye? axons of the retinal ganglion cells
Where does the optic nerve exit the eye? through the lamina cribrosa within the posterior scleral foramen
Approx. how many axons make up the optic nerve? 1.2 million
What structure of what bone does the optic nerve after it passes through the orbit? the optic canal of the lesser wing of the sphenoid bone
What is the optic nerve referred to after it passes the optic canal? intracranial portion
What does the optic nerve merge with afte rit passes the optic canal? the optic chiasm
Ganglion cells within the optic nerve are enveloped by what? myelin sheath
Where is myelin sheath derived from? oligodendrocytes
Axons of the retina ganglion cells within the eye are unmyelinated. What structure must it pass to acquire myelin sheath? lamina cribrosa
What 3 meningeal sheaths surround the optic nerve? tough dura mater (outermost), delicate arachnoid (intermediate), and vascular pia (innerpost)
Where do the 3 meningeal sheaths fuse at? the sclera
What is the subarachnoid space? the space b/w the arachnoid membrane and pia mater
What happens to the subarachnoid space when ICP increases? the cerebrospinal fluid in the subarachnoid space will exert pressure on the nerve
Why does the lamina cribrosa give a convex appearance? this is due to the cerebrospinal fluid that places pressure on the nerve
What happens if ICP increases too much? It will compress the central retina; venous engorgement; papilledema
What 4 divisions can the optic nerve be divided into? intraocular portion, intraorbital portion, intracanalicular portion, intracranial portion
What structures does the intraocular portion include? the optic disc and the portion of the nerve that lies within the sclera
Clinically, what is the prelaminar zone of the optic nerve referred to as? the optic disc
What is the shallow depression that is observed within the disc known as? the optic cup
The optic cup is lined by a glial plaque known as? tissue of Kuhnt or meniscus of Kuhnt
What is the Bergmeister's papilla? an over-esaggerated tissue of Kuhnt
What is the meniscus of Kuhnt continuous with? the inner limiting membrane of Elschnig
Both the meniscus of Kuhnt and the inner limiting membrane of Elschnig are composed of what neuroglial cell? astrocytes
What is the vascularized region b/w the optic cup and the outermost edge of the optic disc? the rum of the optic disc
What envelopes the nerve fiber bundles in the intraorbitral portion? septa that is formed from pial sheath
The length of the intraorbital portion of the optic nerve is 6mm longer than the distance b/w the posterior surface of the eye and the optic canal. How is this advantageous to the eye? it gives the eye greater movement
what surrounds the intraorbital portion of the optic nerve? orbital fat
what is embedded in orbital fat? ciliary vessels and nerves
What 2 structures does the parasympathetic ciliary ganglion lie between? the lateral border of the optic nerve and the lateral rectus muscle
Arterial supply of the optic nerve is supplied from? short posterior ciliary arteries
some of the short posterior ciliary arteries will enter the sclera and form an anastomotic arterial circle with what? the circle of zinn-haller
vessels from the zinn-haller will supply what? most of the capillaries lying within the lamina cribrosa and the pial vasculature
describe the capillaries in the optic nerve? they are nonfenestrated and have zonula occludens
what nourishes the prelaminar portion of the optic disc? retinal capillaries
what supplies blood to the intraorbital portion of the nerve? branches of the pial plexus (it extends into the nerve via pial septa)
what supplies the pial plexus with blood? branches of the ophthalmic artery
the pial plexus supplies what structures with blood? the intracanalicular and intracranial portion of the optic nerve
venous drainage of the optic nerve is through the? central retinal vein
Created by: babytigger131



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