DEVELOPMENT OF THE MEDULLA OBLONGATA
The medulla oblongata develops from the myelencephalon. The early development of the medulla is similar to that of the spinal cord. The appearance of the sulcus limitans divides each lateral wall into a dorsal or alar lamina, and a ventral or basal lamina. Subsequently, the thin roof plate becomes greatly widened as a result of which the alar laminae come to lie dorso-lateral to the basal laminae. Thus, both these laminae are now in the floor of the developing fourth ventricle.
Cells developing in the lateral part of each alar lamina migrate ventrally, and reach the marginal layer overlying the ventrolateral aspect of the basal lamina. These cells constitute the caudal part of the bulbo-pontine extension, and develop into the olivary nuclei . The remaining cells of the alar lamina develop into the sensory nuclei of the cranial nerves related to the medulla. The motor nuclei of these nerves are derived from the basal lamina as described.
The gracile and cuneate nuclei are derived from the lowermost part of the somatic afferent column.
The white matter of the medulla is predominantly extraneous in origin, being composed of fibres constituting the ascending and descending tracts that pass through the medulla.
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