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Serial transverse sections of the brain stem

Mesencephalon.

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Image #30-7
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Serial transverse sections of the brain stem
Mesencephalon.
This section is 5 mm. above the previous level. Within the tegmentum the massive decussation of the brachium conjunctivum (8) occupies a large area. The medial lemniscus (14) is more clearly seen on the right side. It lies close to the surface at this level and is crescent-shaped in cross section. The nucleus (13) of the trochlear nerve lies just above fibers of the medial longitudinal fasciculus (7). The cut passes through the inferior colliculi (11) which lie in the tectum of the mesencephalon. The lateral lemniscus (2, lower pointer) is lateral to and just beneath the nucleus of the inferior colliculus on either side. Some fibers of this bundle enter the colliculus; others ascend, as the inferior quadrigeminal brachium, to reach the medial geniculate body.
1 . Lingual gyrus
2 . Commissure of inferior colliculi (upper pointer) and lateral lemniscus (lower Pointer)
3 . Lateral ventricle
4 . "Alveus"
5 . Hippocampus
6 . Hippocampal gyrus
7 . Medial longitudinal fasciculus
8 . Decussation brachium conjunctivum (superior cerebellar peduncle)
9 . Optic nerve (II)
10 . Arachnoid (within transverse fissure)
11 . Nucleus inferior colliculus
12 . Cerebral aqueduct
13 . Nucleus trochlear nerve
14 . Medial lemniscus
15 . Deep pontine fibers
16 . Longitudinal fasciculus
17 . Superficial pontine fibers
18 . Anterior cerebral artery right
19 . Olfactory tract