Pons Varolii

The pons varolii is a rounded anatomical structure of the central nervous system, lying at the base of the brain. Being part of the brainstem, it is located between the midbrain and the medulla oblongata. Essentially, it is a white thick band of myelinated nerve fibers which links the cerebral cortex and cerebellum with the medulla and spinal cord. Inside the white matter, there are grey nuclei, containing neurons, of the trigeminal nerve, which innervates the muscles of mastication. Blood supply: lateral branches from the basilar artery.

Anatomical Description

The pons consists of two portions: the ventral (anterior part) and the dorsal pons, which is called the pontine tegmentum. The ventral portion is divided into a left and right side by the basilar sulcus, which is a groove that runs down vertically along the midline and through which the basilar artery runs. The pontine sulcus is the horizontal anatomical boundary between the pons and the midbrain (mesencephalon) above, while the inferior pontine sulcus divides it from the medulla oblongata below.

The pons is composed of several bundles of nerve fibers, which arise from different regions of the brain. Thus, it is made up of 1) the corticospinal tract, which originates from pyramidal neurons in the cerebral cortex, extending downwards to the anterior portion of spinal cord; 2) corticopontine tract, which arises from the cerebral cortex, especially from the frontal lobe, ending in the nuclei of the pons; 3) spinocerebellar tracts (anterior and posterior), which connects the cerebellum with the spinal cord; 4) medial leminiscus, which originates from grey nuclei in lower portion of medulla, terminating in the thalamus; 5) lateral leminiscus, which springs from the cochlear nucleus, carrying information about sound; 6) trigeminal nerve nuclei, which are grey masses of nerve cells from which the trigeminal nerve (CN V) arises.

Below, view of ventral aspect of the pons varolii.