Anatomical Features of Cross-sections Through The Midbrain
The midbrain is usually sectioned at the level of the superior and inferior colliculi.
- A transverse cross-section at the level of the superior colliculus shows the red nucleus, the nuclei of the oculomotor nerve (and associated Edinger-Westphal nucleus), the superior cerebellar peduncles or crus cerebri, and the substantia nigra.
- A horizontal cross section at the level of the inferior colluiculus still shows the substantia nigra. Also apparent are the trochlear nerve nucleus, and the decussation of the superior cerebellar peduncles.
- Both sections will show the cerebral aqueduct, which connects the third and fourth ventricle and the periaqueductal gray.
One mnemonic for remembering the structures of the midbrain involves visualizing the mesencephalic cross-section as an upside down bear face. The two red nuclei are the eyes of the bear and the cerebral crura are the ears. The tectum is the chin and the cerebral peduncles are the face and ears.
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