The human brain is one of the most complex and fascinating organs of any species on Earth. Divided into a number of parts, each section has its own distinct functions that ensure the seamless functioning of our body. The brain controls all our functions, like the boss of a company, or the motherboard of a computer. It has 3 main parts – cerebrum, cerebellum and brainstem. The cerebrum controls functions like thinking, reasoning, interpreting touch, vision, etc. The cerebellum is responsible for our balance and coordination. The brainstem consists of the pons, midbrain and medulla oblongata. While the entire brain makes for an extremely interesting read, let us focus on that final part for now.
Medulla Oblongata definition
The medulla oblongata, also known as the medulla, is the lowest part of the brainstem. It develops from an area known as the myelencephalon during our embryonic development. Together with the pons and the cerebellum, the medulla forms the hindbrain or rhombencephalon.
The medulla is conical in shape and tapers ventrally. It lies below the pons and connects the brain to the spinal cord. Measuring about 3 cm in length, and 2 cm at its widest point, this is a tiny, but extremely important, part of our brain.
External Anatomy of the Medulla
On the posterior surface of the medulla, there is a midline fissure, known as the posterior median sulcus (sulcus is a shallow groove). It starts where the 4th ventricle ends, and continues down to the sulcus of the spinal cord. On its side are the fasciculus cuneatus and fasciculus gracilis. These are basically bundles of nerves coming from the upper and lower parts of the body.
On the anterior side, there is also a median fissure. This is continuous with the median sulcus of the spinal cord. However, the decussation from structures called the pyramids interrupts the fissure at certain places. Laterally from the fissure, there is the ventrolateral and posterolateral sulcus.
Internal Anatomy of the Medulla
Similar to the external anatomy, the internal anatomy can also be divided into 2 parts – the ventral medulla and the tegmental medulla.
This consists of the pyramids, olives, and cranial nerves 9-12th rootlets.
The pyramids are located in the middle of the ventral medulla, and are separated by the anterior median fissure. The pyramids are made up of corticospinal tracts. These are bundles of axons that descend from the cerebral cortex and synapse/end in either the brain stem or the spinal cord.
The olives are paired structures located lateral to the pyramid. They are separated from the pyramids by the anterolateral sulcus.
This is the dorsal part of the medulla. It is formed from the bottom part of the 4th ventricle. This contains grey matter, surrounded entirely by white matter. Grey and white matter refer to non-myelinated and myelinated axons, respectively.
The cranial nerves of the medulla also originate from the tegmental part and exit the medulla ventrally.
Medulla Oblongata Function
The medulla acts as the bridge between the brain and the spinal cord. Apart from this, it also controls the Autonomic Nervous System of the body. This part of the nervous system is responsible for controlling the automatic or involuntary actions of our body.
More specifically, it controls functions related to breathing, heartbeat, blood pressure, etc. It is also the center for reflex actions like sneezing, coughing, vomiting, etc.
The medulla controls vasoconstriction and vasodilation of the blood vessels, which adjusts the blood flow rate and is essential for overall health.
The medulla is an extremely important part of the brain, and injuries to it can be fatal. Like any part of the brain, trauma to the medulla can lead to strokes, paralysis, brain death, coma, or even death. Since it controls our involuntary functions, it is arguably the most important part of the brain, and must be protected at all costs!