The medulla oblongata is a vital structure of the central nervous system, which lies at the base of the encephalon (brain), right above the foramen magnum. It is the lower portion of the brainstem as it is located between the pons and the spinal cord, which lies below. The posterior surface of the medulla forms the lowest part of the fourth ventricle floor. Blood supply: it receives oxygenated blood from collateral branches that arise from the left and right vertebral artery.
Function
The medulla oblongata automatically regulates breathing, cardiac rhythm, blood pressure, secretion of saliva as well as peristalsis of stomach and intestines and speech and swallowing as it is the site of grey nuclei of the vagus nerve (CN X), the nucleus ambiguus, and the hypoglossal nerve (CN XII), which controls the muscles of the tongue.
Anatomical Description
The medulla oblongata is a thick, bulb-like structure, which is wider at the top and narrower at the bottom. An anterior and a posterior part can clearly be distinguished. The anterior part is divided into a right and left side by the anterior median fissure. This anterior portion is formed by the decussation of the pyramid, which is the crossing over of nerve fibers of the pyramidal tract that originates from Betz cells (large motor pyramidal neurons) in the cerebral cortex, and the anterior spinocerebellar tract (Gowers column). Embedded in the top part of the anterior side, there is the olivary nuclei, which form the olivary body (olive).
The posterior side of medulla is also divided into a right and left side by the posterior median sulcus. The posterior portion is composed of all the afferent/sensory fibers, which run from the spinal cord to the pons and midbrain. These form separate bands of white fibers, such as the medial lemniscus, the fasciculus gracilis, fasciculus cuneatus, and the lateral spinothalamic tract. The posterior side of medulla contains the nucleus cuneatus, which is the relay station between fasciculus cuneatus and the medial lemniscus.
Below, anterior view of the medulla oblongata, showing the pons and the different cranial nerve roots.
The posterior side of medulla, pons, and cerebellar peduncles.
