MEDULLARY PYRAMIDS Meaning and
Definition
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Medullary pyramids refer to triangular structures found in the medulla oblongata, which is the lower part of the brainstem. They are located on the ventral (anterior) surface of the medulla and are composed of white matter.
The medulla oblongata is an important region of the brainstem responsible for controlling vital functions such as breathing, heart rate, blood pressure, and swallowing reflexes. It serves as a connection between the spinal cord and higher brain structures. The medullary pyramids, along with the adjacent olive-shaped structures called the olive nuclei, are prominent anatomical landmarks in the medulla.
The pyramids contain a collection of nerve fibers known as corticospinal tracts or pyramidal tracts. These tracts are responsible for transmitting motor signals from the cerebral cortex, the outer layer of the brain, to the spinal cord. The corticospinal tracts specifically carry voluntary motor commands, enabling conscious control over movements.
At the caudal end (bottom) of the medulla oblongata, the medullary pyramids undergo decussation, or crossing-over, of the nerve fibers. This means that the fibers originating from one cerebral hemisphere switch sides and continue down the opposite side of the spinal cord. This decussation occurs because the right hemisphere of the brain controls movements on the left side of the body, and vice versa. As a result, the medullary pyramids appear smaller on the side opposite to the originating hemisphere.
In summary, medullary pyramids are triangular structures located on the ventral surface of the medulla oblongata. They contain the corticospinal tracts, which transmit voluntary motor commands from the cerebral cortex to the spinal cord. The crossing-over of nerve fibers
Etymology of MEDULLARY PYRAMIDS
The term "medullary pyramids" comes from a combination of Latin and Greek roots.
"Medullary" is derived from the Latin word "medulla", which means "marrow" or "middle". In anatomy, it refers to the innermost part of an organ or structure.
"Pyramids" is derived from the Greek word "pyramis", which means a pyramid-shaped structure. It is a direct reference to the shape of the structures found in the medulla oblongata of the brain.
In the context of the nervous system, the medullary pyramids are two large bulges on the anterior surface of the medulla oblongata, which is the lower part of the brainstem. These pyramidal-shaped structures contain the corticospinal tracts, which are responsible for conveying motor signals from the brain to the spinal cord.
