Reference > Anatomy of the Human Body > Page 782
traverse the medulla, pass between the medial accessory and the inferior olivary nuclei. (c) The dorsal accessory olivary nucleus is the smallest, and appears on transverse section as a curved lamina behind the inferior olivary nucleus.
  6. The nucleus arcuatus is described below with the anterior external arcuate fibers.

Inferior Peduncle (restiform body).—The position of the inferior peduncles has already been described (page 775). Each comprises:
  (1) Fibers from the dorsal spinocerebellar fasciculus, which ascends from the lateral funiculus of the medulla spinalis.
  (2) The olivocerebellar fibers from the opposite olivary nucleus.
  (3) Internal arcuate fibers from the gracile and cuneate nuclei of the opposite side; these fibers form the deeper and larger part of the inferior peduncle.

FIG. 697– Nuclei of origin of cranial motor nerves schematically represented; lateral view. (See enlarged image)

  (4) The anterior external arcuate fibers vary as to their prominence in different cases: in some they form an almost continuous layer covering the pyramid and olive, while in others they are barely visible on the surface. They arise from the cells of the gracile and cuneate nuclei, and passing forward through the formatio reticularis, decussate in the middle line. Most of them reach the surface by way of the anterior median fissure, and arch backward over the pyramid. Reinforced by others which emerge between the pyramid and olive, they pass backward over the olive and lateral district of the medulla oblongata, and enter the inferior peduncle. They thus connect the cerebellum with the gracile and cuneate nuclei of the opposite side. As the fibers arch across the pyramid, they enclose a small nucleus which lies in front of and medial to the pyramid. This is named the nucleus arcuatus, and is serially continuous above with the nuclei pontis in the pons; it contains small fusiform cells, around which some of the arcuate fibers end, and from which others arise.


