Human Anatomy - Kotsan I. Y. 2009

Brain
Internal structure of the medulla oblongata

The Medulla Oblongata evolved in connection with The Development of the Organs of gravity and Hearing, as well as the branchial apparatus involved in Respiration and Blood Circulation. Consequently, it contains nuclei of Gray matter that ensure equilibrium and coordination of movements, and regulate METABOLISM, respiration, and circulation:

1. The olivary Nucleus (nucleus olivaris) resembles a curved lamina of gray matter open medially. It connects with the dentate Nucleus of the Cerebellum and serves as an intermediate center of equilibrium. The olivary nucleus is most prominent in humans, whose upright posture requires a highly refined gravitational apparatus.

2. The nuclei of four pairs of lower Cranial Nerves (IX, X, XI, XII), which participate in the Innervation of the derivatives of the branchial apparatus and Internal Organs.

3. Vital respiratory and circulatory centers associated with the nuclei of the Vagus nerve. Therefore, damage to the medulla oblongata can result in death.

4. The reticular formation (formatio reticularis), formed by an interwoven network of nerve fibers and interspersed Nerve Cells.

The White matter OF the medulla oblongata contains both long and short fibers.

The long fibers include descending Pyramidal Tracts that pass transitively into the anterior funiculi of the Spinal Cord and partially decussate in the region of the pyramids. Additionally, the nuclei of the posterior funiculi (gracile and cuneate nuclei) house The Cell bodies of second-order Neurons belonging to ascending sensory pathways; their fibers extend from the medulla oblongata to the thalamus, forming the bulbothalamic tract (tractus bulbothalamicus). The fibers of this bundle form the medial lemniscus (lemniscus medialis), which undergoes the sensory decussation (decussatio lemniscorum) within the medulla oblongata and continues upward as a bundle of fibers positioned dorsal to the pyramids, between the olives. Thus, the medulla oblongata features two long pathway decussations: a ventral motor decussation and a dorsal sensory decussation.

The short pathways comprise bundles of nerve fibers connecting individual gray matter nuclei to one another, as well as linking the nuclei of the medulla oblongata with neighboring Regions of the Brain. Notable among these are the olivocerebellar tract (tractus olivocerebellaris) and the medial longitudinal fasciculus (fasciculus longitudinalis medialis), which is located dorsal to the interolivary layer.