The Anatomy of the Medulla Oblongata

The medulla oblongata relays critical signals between the brain and body

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The medulla oblongata carries signals from the brain to the rest of the body for essential life functions like breathing, circulation, swallowing, and digestion. Making up a tail-like structure at the base of the brain, the medulla oblongata connects the brain to the spinal cord, and includes a number of specialized structures and functions. While every part of the brain important in its own way, life cannot be sustained without the work of the medulla oblongata.

medulla oblongata
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Anatomy

The medulla oblongata is one of the three parts of the brainstem, along with the midbrain and the pons. These three collaborating structures are located in front of the cerebellum at the base of the brain and connect to the spinal cord.

Made up of both white and gray matter, the cone-shaped medulla oblongata is formed about 20 weeks into gestation from the end of the neural tube in embryos. In adulthood, its functions are divided into sections, which each perform their own role.

Structure

The posterior—or back—of the medulla is divided into two parts. The superior section connects to the fourth ventricle of the brain, and the inferior section connects to the spinal cord through the median fissure. The brainstem—including the midbrain, pons, and medulla—come together to house the originating points of 10 of the 12 cranial nerves, which control all of the body’s basic functions.

Function

The brainstem controls the autonomic nervous system, or the functions that the body performs without thought like breathing, maintaining blood pressure and temperature, circulating blood, and digesting. It also houses the reticular activating system, which regulates sleep patterns, and allows you to wake up and interact with the world around you.

The work of the brainstem originates and is carried through the body by the cranial nerves. Ten of the body’s 12 cranial nerves being in the brainstem, with the first two cranial nerves controlling smell and vision originating higher up in the brain. Cranial nerves three through eight begin in the midbrain and pons, and nerves nine through 12 begin in the medulla.

  • Cranial nerve 9 is the glossopharyngeal nerve, and it controls swallowing, taste, and saliva production.
  • Cranial nerve 10 is the vagus nerve, which plays a role in breathing, heart function, and digestion. This nerve is also the source for parasympathetic stimulation, which controls hormone release.
  • Cranial nerve 11 is the accessory nerve, and controls the muscles in the upper back and neck. Without this nerve function, you could not turn your head or shrug your shoulders.
  • Cranial nerve 12 is the hypoglossal nerve. This nerve controls tongue movement and is crucial to speech and swallowing.

Together, all of these sections of the brainstem and the nerves it houses relay signals for the most basic life functions from the brain to the spinal cord and on to the rest of the body.

Associated Conditions

Rare malformations in the medulla can occur at birth, but many of the problems associated with this area or due to physical injury, or injuries that can impact this part of the brain such as drug overdoses or strokes. In cases where the medulla is damaged, the critical functions controlled there may be interrupted, resulting in severe disability or brain death. Without the function of the medulla and the other two areas of the brain stem, survival is not possible.

There are a number of specific conditions that can affect the medulla, as well:

  • Lateral Medullary Syndrome (Wallenberg Syndrome): This is the common form of stroke that affects the medulla. Caused by either a clot in the vertebral artery, or dissection of that artery, this syndrome can result in headache, pain, vertigo, trouble swallowing or speaking, and lack of sensation in the face.
  • Medial Medullary Syndrome (Dejerine Syndrome): Caused by occlusion, or a blockage, in the vertebral or spinal artery, this condition results from a lack of blood blow through parts of the medulla causing paralysis in areas like the legs, arm, face, and possibly tongue.
  • Bilateral Medial Medullary Syndrome: This is a rare combination of the two syndromes referenced above, and results in almost complete quadriplegia. Facial nerves and respiratory function are often spared damage in this syndrome.

Tests

Detecting damage to the medulla and other parts of the brain stem can be difficult, as people who have injuries here may not be able to fully participate in an examination. The following are a few examples of tests that may be done to determine the level of function in the brainstem.

  • Cranial nerve assessment: A physical assessment that allows a medical provider to see what functions may be impaired based on what tasks you are able to perform.
  • Computer Tomography (CT) scan or Magnetic Resonance Imaging (MRI): These will help a provider visualize areas of damage.
  • Brain Perfusion Scan: These tests allow doctors to see which areas of the brain are receiving blood flow, and are useful in diagnosing brain death.
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  1. American Association of Neurological Surgeons. Anatomy of the Brain. Updated 2020.

  2. Iordanova, R, Reddivari, AKR. Neuroanatomy, Medulla Oblongata. StatPearls. Updated Nov. 15, 2019.

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