Medulla oblongata


The most inferior portion of the brain stem, only about 3 centimeters long, is the medulla oblongata. The structure is actually bulbous in design and is a continuation of the pons anteriorly and continuous with the spinal cord posteriorly. This all takes place at the same level as the foramen magnum. When viewing from the external side, the medulla oblongata resembles very closely the spinal cord, with the exception of the pyramids. The pyramids are two triangular elevated elements which are bound on the inferior side as is the oval shaped enlarged area known as the olive which is housed on each individual lateral surface. The space that is marked in medulla oblongata is known as the fourth ventricle. This is a posterior continuation of the central canal of the spinal cord. The anterior continuation runs with the mesencephalic aqueduct.


Vital nuclei and white matter comprise the medulla oblongata, as well as creates the tracts of communication which ascend and descend along the spinal cord and other necessary portions of the brain. The medulla oblongata contains the pyramidal region, which is where the fibers of the tracts overlap and cross over to the other side of the brain. This design allows the brain to send information to the opposite side of the body when needed. This also permits the opposite side of the body to send information to the opposite side of the brain. The medulla oblongata’s gray matter hosts a variety of vital nuclei reserved for cranial nerves and sensory relay. The hypoglossal nucleus and the nucleus ambiguous create the center structure which together brings forth the glossopharyngeal accessory and the hypoglossal nerves. The vestibulocochear nerves are formed from the vestibular nuclei. On each of the individual lateral sections of the medulla oblongata, the vagus neuclei create the vagus nerves. This lies in juncture with the fourth ventricle.


Medulla Oblongata
Image: Medulla Oblongata

Responsible for relaying sensory information to the thalamus are the nucleus gracilis and the nucleus coetaneous. From the thlalamus, the sensory information is then relayed to the cerebral cortex via the thalamic nucleus. There are then two nuclei responsible for the passing of information from the forebrain to the midbrain. These would be the inferior olivary nuclei and the accessory olivary nuclei. This allows the olive to be the mediary go between for the forebrain and the midbrainvia the inferior cerebellar peduncles of the cerebellum.


Responsible for the autonomic control of numerous visceral organs, the medulla oblongata houses three additional centers for regulation and control. The cardiac center is created by both inhibitory and acceleratory fibers which create the necessary functions for the cardiac center. Inhibitory impulses are chronically running to the heart via the vegus nerves to instruct the heart to slow down the rate. The acceleratory impulses run along the spinal cord and conjoin with the spinal nerves T1 through T5 in order to quicken the heart rate when necessary.


Image: Myelencephalon

The vasomotor center is responsible for sending impulses through the spinal cord to the spinal nerves directly to the walls of the muscles surrounding the arteries and causing arterial constriction in order to elevate the arterial blood pressure when necessary. The respiratory nuclei of the respiratory center create control within the medulla oblongata of the depth and rate of breathing. This functions in unison with the respiratory nuclei of the pons, which regulates rhythmic breathing.

The medulla oblongata houses other various nuclei which controls reflex functions such as sneezing, coughing, vomiting, and swallowing. These functions can either be completely involuntary or may begin as voluntary functions which then turn into involuntary actions.


The myelencephalon houses the medulla oblongata which is responsible for adjoining to the spinal cord. This is also the housing for the various nuclei related to the cranial nerves and vital autonomic functions.

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