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Medulla Oblongata

The medulla oblongata is a formation that is present in the brain of most vertebrate animals, which includes humans as well. This part of the brain is a very essential structure as it is responsible for the control of a number of autonomic functions such as blood pressure and respiration. Any extensive trauma or injury to the medulla oblongata can be life threatening as the affected individual will be unable to swallow or breathe or even carry out basic motor functions without help. The medulla oblongata is also thought to be a vital part in the study of anesthesia, as anesthetics are thought to depress the functionality of medulla oblongata and prevent it from performing normally.

This part of the brain is situated at the lower end of the brainstem and is a structure that connects the spinal cord and the brain. It is present just above the spinal cord and just below that region of the brainstem referred to as pons. In a cross section, the medulla oblongata can be observed as a tiny protuberance in the brain stem that is intended to accommodate various types of essential nerves.

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Besides important functions such as blood pressure and respiratory regulation, the medulla oblongata is also a part of other body functions such as different kinds of bodily secretions, reflexes, cardiac performance and swallowing. Such functions that are carried out by the medulla oblongata at any time of the day or night, without the need for any input or signals from the rest of the brain. Response to some types of stimuli and the creation of reflex actions and responses which are essential for the effective functioning of the body are also controlled by the medulla oblongata. The capacity to respond spontaneously to certain types of stimuli and the independent conduct of vital functions like swallowing and breathing are essential for survival and hence medulla oblongata functions independently.

Individuals who are affected by brain injury or trauma can continue to have functioning bodies, in case the medulla oblongata remains intact and working. Any damage or injury to the medulla oblongata increases the need for supportive equipments like a ventilator or others to allow the body to keep working. The severity of damage to the medulla oblongata determines the ability of an affected individual to recover from the trauma. If the damage is extensive, then the said individual is believed to be brain dead or in a chronic vegetative state, which have no options of any sort of recovery. The body will stop functioning, when life support systems are withdrawn.

There are a number of medications and drugs that can result in alterations in the working of medulla oblongata. Such drugs can sometimes lead to a physical state that is similar to death. Alcohol as well as opiates can lead to dysfunction of the medulla oblongata, till such time when the substances are removed from the body. Overdose of opiates and other such drugs prevent the medulla oblongata from functioning effective and hence it results in fatalities due to overdose. Medical conditions such as coma and hypothermia as well as sedatives can also lead to such life threatening situations

Thus the main functions of medulla oblongata are as follows:

  • Relay of nerve signals between the spinal cord and brain: The sensory and motor neurons that begin in the forebrain and midbrain pass through the medulla oblongata. It is thus a component of the brainstem, which assists in the transfer of messages between the spinal cord and various sections of the brain.
  • Control and regulation of autonomic functions
  • Coordination of motor movements

The anatomy of medulla oblongata

It is divided into two parts. An open part where the fourth ventricle forms the dorsal surface and a closed part where the metacoel is present inside the medulla oblongata

Between the anterolateral sulcus and the anterior median sulcus:

  • The area between the anterolateral sulcus and the anterior median sulcus contains a raise on either side referred to as the pyramid of medulla oblongata. It is caused due to the corticospinal tract.
  • Some of these fibers cross others in the lower region of medulla, causing destruction of the anterior median fissure. Such a process is called the decussation of the pyramids
  • Other fibers beginning from the anterior median fissure which are present laterally on the pons surface are called external arcuate fibers.

Between posterolateral sulci and the anterolateral

  • The upper area of medulla between posterolateral sulci and the anterolateral has a swelling called Olivary body, which is caused by a big mass of gray matter called inferior olivary nucleus

Between the posterolateral sulcus and the posterior median sulcus

  • In the posterior of medulla, tracts enter the area between the posterolateral sulcus and the posterior median sulcus from the spinal cord posterior funiculus
  • These fasciculi, caused by masses of gray matter called the nucleus cuneatus and the nucleus gracilis, end in curved elevations known as the cuneate tubercles and the gracile
  • The posterior of medulla above the tubercles contains a triangular fossa, which is constrained on both sides by the inferior cerebellar peduncle

Lower part

  • It has a longitudinal elevation called the tuberculum cinereum, which is present just lateral to the fasciculus cuneatus. This is the result of accumulation of gray matter referred to as the spinal nucleus of the trigeminal nerve.
  • This gray matter is enclosed by a layer of nerve fibers which form the trigeminal nerve spinal tract

Base

  • The base contains the commissural fibers that go from the ipsilateral side in the spinal cord to the contralateral side in the brainstem. Below the base is the spinal cord

Medulla Oblongata cross section

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