Part3 Flashcards
What is the fiber pattern layout?
The more peripheral the origin of a nerve fiber, the more external its location in the nerve fiber layer and in the optic nerve.
How are the largest pores of the lamina cribrosa arranged?
Hourglass configuration superiorly and inferiorly.
Ganglion cell axons pass through these pores. THese cells are affected first in glaucoma because CT tissues suck superiorly and inferiorly.
What are two features of the postlaminar region?
- Myelination of axons from lamina cribosa to the terminal nuclei in the brain
- The meninges surrounding the brain.
Astrocytes
Glial cell that is mainly part of the prelaminar portion.
Central caudate sub-nucleus
Belongs to CN III nucleus.
Is single and control both levators.
Ed Wes nucleus is….
Another exception to CNIII nucleus having paired subnuclei corresponding to each muscle.
Single at one end but divided into two at its anterior end.
What does superior division of CNIII innervate?
LPS and SR
What does inferior division of CN III innervate?
MR, IO, IR
Does Ed-Wes nucleus give rise to sympathetic or parasympathetic branches?
Parasympathetic
Parasymp branches from CNIII is for…
Iris sphincter and ciliary muscle
Inferior division
Sympathatic branches from CNIII is for….
Superior tarsal muscle-open up your big eyes.
Superior Division
What does 1:3 represent?
The nerve to muscle fiber ratio. One nerve for every three muscles in the body.
Are there more postganglion fibers or less preganlionic fibers for the inferior division?
More postganglionic fibers.
This means the system is diffuse.
What does CN IV paralysis consist of?
- Vertical squint
- Can’t lookdown when eye is in adducted position because SO is the only depressor in the adducted position.
- Head tilt - downward and towards the normal side to avoid diplopia.
- The affected ye rotates medially producing diplpia when looking downwards.
Which cranial nerve is the most vulnerable?
CN VI.
Any cerebral lesion no matter what distance can damage it.
Where is the nucleus of CN VI found?
Floor of the 4th ventricle close to the median plane.
What is CN VI paralysis?
Inability to abduct the eye beyond the straight ahead gaze.
Diplopia on looking into the direction of the affected side.
What is the origin CN II?
Retinal ganglion cells.
Layers 1 & 2 of LGN?
Magnocellular
Mixed ON & OFF
Layers 3-6 of LGN?
Parvocellular
Contralateral?
1, 4, 6
Optic chism-crossover fibers?
Inferior nasal and superior nasal fibers both crossover; but the inferior nasal fibers is more lateral than the medial fibers.
Superior temporal vs Inferior temporal
Both will stay on the ipsilateral side of the eye; but the Superior temporal will be more medial.
Where are the macular fibers located in the optic tract?
Located in between.
What is the preganglion neuron location for the SNS?
Lateral horn of spinal cord
What is the postganglion neuron location for SNS?
Superior cervical ganglion.
How do SNS fibers enter the eye?
Short ciliary nerves
Long ciliary nerves
Rami oculares
Blood vessels.
What are the orbital distribution of SNS fibers?
Lacrimal gland (blood vessels)
Superior & Inferior tarsal muscles
Orbital muscle of Mueller
Orbital blood vessels.
What is the ocular distribution of SNS fibers?
Dilator M. Sphincter M. Ciliary M. Ocular blood vessels Trabeculum
What do CN III and VII have in common?
Both have PNS innervation
Where is the preganglionic neuron for CN III located?
CN III nucleus (midbrain, sup collic)
Where is the preganglionic neuron for CN VII located?
CN VII nucleus (pons-middle)
Where is the postganglionic neuron for CN VII located?
Pterygopalatine ganglion
Where is the postganglionic neuron for CN III located
Ciliary ganglion
How does PNS fibers enter the eye?
Short ciliary Nerves (CN III)
Rami Oculares (CN VII)
This differs from SNS which has 4.
What are the orbital distribution of PNS?
Similar to SNS minus the Mueller muscles. Have: Lacrimal gland Superior & Inferior tarsal muscle Blood vessels ALl of these is from CN VII
What are the ocular distribution of PNS
Same as SNS
What are the three actions that result from corneal reflex?
Miosis
Lacrimation
Blinking
Disruption of the sympathetic pathway?
Horner’s syndrome
Symptoms of Horner’s syndrome
Miosis: usual tone for dilator muscle is gone
Anisocoria: pupil constriction for affected eye
Anhidrosis: absense of sweat secretion
What cells of the iris form the iris stroma and anterior border layer?
Fibroblasts and melanocytes that derived from neural crest cells.
Early layer of cells is known as the pupillary membrane.
How do the anterior and posterior epithelial layers of the iris come about?
two layers of cells on top of the optic cup multiply and grow inward beneath the stroma.
T/F?
Pupil is the last structure to be formed.
True.
Ant and post epi cells do not grow in the center.
The iris stroma needs to be removed around this central region or the epithelial free zone.
Where are the sphincter pupillae and dilator pupillae muscle formed from?
From the anterior epithelium.
Neuroectoderm origin
Sphincter develops before dilator
Iris blood vessels
Branches of major arterial circle forming in the developing ciliary body.
Mesodermal origin.
How do choroidal capillaries first appear?
At the posterior pole and then differentiate peripherally.
Talk about choroidal circulation?
Choriocapillaris forms first (around 2 months), then the short posterior ciliary arteries (Haller’s and Sattler’s) are added to supply choriocapillaris.
Pt 2: long posterior ciliary arteries bypass developing choroid and contribute to circulation in anterior aspect of eye.
1. Tunica vasculosa lentis
2. Annular vessel
3. Major arterial circle
4. Intramuscular arterial circle.
