Question:hard
All of the following are seen in the floor of the third ventricle except?
All of the following are seen in the floor of the third ventricle except?
Show Hint
It is the chiasma, not a developmental stalk, that lies in the floor.
Updated On: Jun 24, 2026
- Infundibulum
- Oculomotor nerve
- Mammillary body
- Optic stalk
Show Solution
The Correct Option is D
Solution and Explanation
Work through the adult landmarks that line the floor of the third ventricle and discard the one that is not a true floor structure. Running anteriorly to posteriorly, the floor is built by the optic chiasma, the tuber cinereum bearing the infundibulum, the paired mammillary bodies, the posterior perforated substance, and the midbrain tegmentum. From the options, the infundibulum and the mammillary bodies sit squarely within this list, and the oculomotor nerve is closely related as it exits through the interpeduncular region of the floor. The remaining choice, the optic stalk, is an embryological connection between the early optic vesicle and the diencephalon that matures into the optic nerve; in the formed brain the corresponding floor landmark is the optic chiasma, not a stalk. Because the optic stalk is a developmental remnant and not an adult floor component, it is the exception. \[\boxed{\text{Optic stalk}}\]
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