'A' is the inferior olivary nucleus. There are accessory nuclear masses on its medial and dorsal sides. Together these are responsible for the elevation of the olive on the ventrolateral surface of the medulla.

The huge bundle of fibres emerging from the nucleus crosses over to the opposite side to reach the cerebellum (olivocerebellar fibres). This, then, is the third major deccusation in the medulla oblongata.

The area in the white outline has the same tracts we mentioned with the previous section - from ventral to dorsal side the large pyramidal tracts (underlying the pyramids of the medulla), the medial lemniscus and the medial longitudinal fasciculus.

The black outline includes the hypoglossal nerve nucleus. Lateral to it is the area of the dorsal motor nucleus (GVE) of the vagus. Ventrolateral to the XII nucleus would be the nucleus ambiguus (SVE) which will continue rostrally as the SVE nucleus of the IX. The sensory nuclei would be more lateral, among them the nucleus of the tractus solitarius receiving visceral afferent input (for those interested in detail : caudal part - general, rostral part - special, i.e. taste fibres). In some pictures you may see the fibres of the nerves - hypoglossal emerging between the pyramid and the olive and the IX / X / XI lateral to the olive. In the yellow outline are the spinal tract and nucleus of V, as also the spinothalamic tracts (also called the spinal lemniscus).

In the area dorsal to the yellow outline, the inferior cerebellar peduncle is becoming thicker as more and more fibres from the olive accumulate there. Based on functional lines, can you name a few other components of the inferior cerebellar peduncle?

If you wish to name this section you may call it a section at the midolivary level.