Intracranial portion of the optic nerve Flashcards
Why is the optic pathway effectively a tract within the CNS? 2 reasons
- retinae develop as evaginations of the diencephalon
- optic nerves are covered by layers of meninges; the corneoscleral envelope and uveal tract of the eye are homologous to the dura mater and pia-arachnoid respectively
What structures around the visual pathway are analogous to the lining of the nervous system?
- corneoscleral envelope = dura mater
- uveal tract = pia-arachnoid
Explain what A, A’, B, B’ and so on indicate on the following diagram:
- the manner of retinotopic projection to the lateral geniculate nucleus (LGN) and the ocular dominance columns in the primary visual cortex from left and right eyes are illustrated by three imaginary points or images (A, B, C) from the left visual field (not shown) falling on the right half of each retina (A, B, C in left eye and A′, B′, C′ in right eye).
What happens to the optic nerves after they leave the cranial end of the optic canal?
- pass medially, backwards and slightly upwards within the subarachnoid space of the middle cranial fossa
- end by forming optic chiasma in the floor of the third ventricle
Where is the optic chiasma located?
floor of third ventricle
What are 3 important relations of the optic nerve?
- olfactory racts
- frontal lobe (gyrus rectus - most medial margin of inferior surface of frontal lobe)
- anterior cerebral arteries above
How are the internal carotid arteries related to the intracranial portion of the optic nerve?
each internal carotid artery as it emerges from the roof of the cavernous sinus lies lateral to the junction of the optic nerve and chiasma
What lies below the optic nerves? 2 things
- jugum of sphenoid
- sulcus chiasmaticus or optic groove
What is being shown in the image?
each internal carotid artery lies lateral to junction of optic nerve and chiasm
