Figure 67 midmedulla photographic view

This is a photographic image, enlarged, at the middle level of the medulla, with the cerebellum attached. This specimen shows the principal identifying features of the medulla, the pyramids ventrally on either side of the mid-line and the more laterally placed inferior olivary nucleus, with its scalloped borders.

Between the olivary nuclei, on either side of the mid-line, are two dense structures, the medial lemniscus. The other dense tract that is recognizable in this specimen is the inferior cerebellar peduncle located at the outer posterior edge of the medulla. Other tracts and cranial nerve nuclei, including the reticular formation, are found in the central region of the medulla, the tegmentum.

The space behind is the fourth ventricle, narrowing in its lower portion (see Figure 20B). There is no "roof' to the ventricle in this section, and it is likely that the plane of the section has passed through the median aperture, the foramen of Magendie (see Figure 21).

The cerebellum remains attached to the medulla, with the prominent vermis and the large cerebellar hemispheres. The cerebellar lobe adjacent to the medulla is the tonsil (see Figure 18; discussed with Figure 9B). The extensive white matter of the cerebellum is seen, as well as the thin outer layer of the cerebellar cortex.

The medulla is to be represented by three sections:

• Figure 67 A: The upper medullary level typically includes CN VIII (both parts) and its nuclei.

• Figure 67B: This section through the mid-medulla includes the nuclei of cranial nerves IX, X, and XII.

• Figure 67C: The lower medullary section is at the level of the dorsal column nuclei, the nuclei gracilis and cuneatus.

Inferior Cerebellar Peduncle

Dentate nucleus

Vermis of cerebellum Tonsil of cerebellum

Foramen of Magendie

Inferior cerebellar peduncle

Cerebellar cortex

Medial lemniscus Inferior olivary nucleus

Cortico-spinal tract (pyramid)

Ch = Cerebellar hemisphere

FIGURE 67: Brainstem Histology — Medulla (mid — photograph)

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