This separates the medial motor neurons from the lateral sensory neurons. Lateral to all these bumps previously discussed is an indented line, or sulcus that runs rostrally, and is known as the sulcus limitans. Instead, they have facial nerve axons traversing superficial to underlying abducens (CN VI) nuclei. Each facial colliculus, contrary to their names, do not contain the facial nerve nuclei. These fibers are known collectively as the striae medullares.Ĭontinuing in a rostral direction, the large bumps are called the facial colliculi. Superior to these trigones are fibers running laterally in both directions. Underlying each of these are motor nuclei for the respective cranial nerves. In the midline and directly superior to the obex is the vagal trigone and superior to that it the hypoglossal trigone. In the floor of the 4th ventricle, various nuclei can be visualized by the small bumps that they make in the overlying tissue. Superior to the obex is the floor of the 4th ventricle.
Lateral to the fasciculi cuneatus is the lateral funiculus. The posterior intermediate sulci separates the fasciculi gracilis from the fasciculi cuneatus. The obex marks the end of the 4th ventricle and the beginning of the central canal. Underlying these are their respective nuclei. Superior to each of these, and directly inferior to the obex, are the gracile tubercles and cuteanus tubercles, respectively. Moving laterally on each side is the fasciculus gracilis, and lateral to that is the fasciculus cuneatus. The most medial part of the medulla is the posterior median fissure. Laterally, the trochlear nerve has emerged after emerging out of the dorsal rostral pons and wrapping around to the anterior. At the rostral pons, the occulomotor nerve emerges at the midline. At the level of the midpons, the large trigeminal nerve, CN V, emerges. These cranial nerves are the abducens nerve, facial nerve and the vestibulocochlear nerve, respectively. Between the basal pons, cranial nerve 6, 7 and 8 emerge (medial to lateral). The pyramids end at the pontomedullary junction, noted most obviously by the large basal pons. Lateral (and dorsal) to the olives are the rootlets for cranial nerves IX and X ( glossopharyngeal and vagus, respectively). The olives are swellings in the medulla containing underlying inferior olivary nuclei (containing various nuclei and afferent fibers).
Lateral to these rootlets and the anterolateral sulci are the olives. Emerging from the anterolateral sulci are the hypoglossal nerve (CN XII) rootlets. The anterolateral sulcus is lateral to the pyramids. The pyramids contain the fibers of the corticospinal tract, or the upper motor neuronal axons as they head inferiorly to synapse on lower motor neuronal cell bodies within the ventral horn of the spinal cord. Moving laterally on each side are the pyramids. The most medial part of the medulla is the anterior median fissure. General anatomy Ventral view/medulla and pons
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