The pons is a small primitive structure in the mammalian brain. By primitive, researchers mean that it is found in mammals considered to have evolved before Homo sapiens. The structure itself is small and appears insignificant compared to other more complex structures of the human brain. However, it is a very important structure for motor functions (movement) of many regions of the body. Its primary function seems to be one of integrating signals from the cerebrum to the cerebellum and sending them to the proper parts of the body. Another function involves the formation of several of the cranial nerves for the head.
When looking at fetal development of the brain, the developing pons is found at the point where the brainstem flexes or bends back on itself and eventually comes in contact with the growing cerebellum. As a result of the bending, the fourth ventricle lies just next to the adult pons. The ventricle is the remnant of the initial space between the cerebellum and the pons. This spot is simply called the pons curvature.
At one time the pons was termed the pons Varolii, but as the trend to drop personal names from anatomical structures continues, this name also name has been dropped.
The pons is anterior (front of body) swelling of tissue on an area called the hindbrain or metencephalon. It is located above (superior) to the medulla oblangata, below (inferior) to the crura cerebri, and in the middle or between the two hemispheres (sides) of the cerebellum. It is a tiny structure being only about an inch long and thick and about and an inch and one half wide. The pons is directly connected to the medulla and the midbrain. Its sides are free and it is separated from the cerebellum by the cerebro-spinal fluid in the fourth ventricle.
As mentioned, the pons receives motor signals from the cerebellum and uses the Purkinje motor neurons to send the impulses to the proper regions of the body. These nerve tracts are seen as white fibers from side to side throughout the entire structure. The reticular ( a latticework type pattern) formation of the medulla extends into the top portion of the pons. The reticular formation aids in the regulation of sleep and other daily cycles of the brain.
Several of the cranial nerves have their nuclei located in the pons. The nuclei lead to fibers that emerge from the pons and out to regions of the face. Cranial nerves V (trigeminal), VI (abducens), VII (facial), VIII (vestibulucochlear) come from the junction of the pons with the medulla.
The gray matter of the pons is the unmyelinated portion of the structure. Its function is to relay signals from the cerebrum to the cerebellum. Without this relay, motor functions necessary for breathing, posture, swallowing, and bladder control would be difficult if not impossible.
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