Optic chiasma Flashcards
Where is the optic chiasma located?
junction of anterior wall and floor of third ventricle, 5-10mm above diaphragma sella and hypophysis cerebri
What is the optic chiasma?
flattened quadrangular bundle of nerves measuring 12 x 8 mm whose anterolateral angles are continuous with the optic nerves and posterolateral angles form optic tracts
What lies in front of the optic chiasma?
it usually lies just behind optic groove or sulcus chiasmatius; rarely might lie partly within sulcus
What is the tuber cinereum?
sheet of grey matter that forms a median eminence around the base of the pituitary stalk or infundibulum
Where is the tuber cinereum in relation to the optic chiasm?
lies behind and below the chiasma between the mamillary bodies
What is the importance of the mamillary bodies?
important as a memory relay to the hippocampus
What is an important lateral relation of the optic chiasma?
anterior perforated substance
Which blood vessels pass above the optic chiasm?
the anterior communicating artery passes between the two anterior cerebral arteries and lies above the chiasma
What is the partial crossing of optic nerve fibres in the optic chiasma an essential requirement for?
binocular vision
Which fibres cross at the chiasm?
fibres from the nasal hemiretina of each eye cross at the midline to enter the contralateral optic tract, after taking a short loop in the ipsilateral tract or into the contralateral optic nerve
What happens before optic fibres from the nasal hemiretina cross at the optic chiasm?
they take a short loop in the ipsilateral tract or into the contralateral optic nerve
