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Hindbrain. Pons: external and internal structure. Cerebellum: external and internal structure, nucleuses of cerebellum, their function. The cavity of the hindbrain

The rhombencephalon (or hindbrain) is a developmental categorization of portions of the central nervous system in vertebrates. It includes the medulla, pons, and cerebellum. Together they support vital bodily processes. The rhombencephalon can be subdivided in a variable number of transversal swellings called rhombomeres.

The pons is part of the brainstem that links the medulla oblongata and the thalamus. It is cranial to the medulla oblongata, caudal to the midbrain, and ventral to the cerebellum. The pons in humans measures about 2.5 cm or 1 inch in length. Most of it appears as a broad anterior bulge rostral to the medulla.

The pons contains nuclei that relay signals from the forebrain to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.

Within the pons is the pneumotaxic center, a nucleus that regulates the change from inspiration to expiration.

The cerebellum is a region of the brain that plays an important role in motor control. At the level of gross anatomy, the cerebellum consists of a tightly folded and crumpled layer of cortex, with white matter underneath, several deep nuclei embedded in the white matter, and a fluid-filled ventricle at the base. At the microscopic level, each part of the cortex consists of the same small set of neuronal elements, laid out with a highly stereotyped geometry. At an intermediate level, the cerebellum and its auxiliary structures can be decomposed into several hundred or thousand independently functioning modules called "microzones" or "microcompartments".

In general, each pair of deep nuclei is associated with a corresponding region of cerebellar surface anatomy.

-The dentate nuclei are deep within the lateral hemispheres,

-the interposed nuclei are located in the paravermal (intermediate) zone,

-and the fastigial nuclei are in the vermis.

The cavity of the hind brain forms part of the ventricular system of the brain and is called the fourth ventricle. It is continuous above with the cerebral aqueduct and below with the central canal of the spinal cord.Fourth ventricle is the part of the ventricular system from where the cerebrospinal fluid exits into the subarachnoid space.

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