Hindbrain is the most posterior and inferior part of brain that connects to the spinal cord. It consists of three parts: Pons, Medulla oblongata and Cerebellum. The cavity of the hindbrain forms the fourth ventricle.
Pons is situated below the midbrain and above the medulla oblongata anterior to the cerebellum. It is mainly composed of those nerve fibers that connect the two halves of cerebellum. In addition, it also contains the ascending and descending fibers connecting the forebrain, midbrain and the spinal cord.
Some of the neurons of pons serve as relay stations, while others form cranial nerve nuclei.
It is the inferior-most component of brain that is continuous below with the spinal cord. Structurally, it is conical in shape and contains a median fissure on the anterior surface, on either side of which is a swelling called the pyramid. These pyramids are formed by bundles of nerve fibers that originate in the motor cortex of cerebrum.
Some other important structures of medulla oblongata are:
- Olives: Oval elevations, posterior to the pyramids, produced by the underlying olivary nuclei.
- Inferior cerebellar peduncles: These lie behind the olives and connect the medulla to the cerebellum.
- Gracile and cuneate tubercles: They are present on the on the posterior surface of the inferior part of medulla. They are produced by underlying nucleus gracilis (medial) and nucleus cuneatus (lateral).
Cerebellum is the second largest part of brain (after cerebrum). It lies within the posterior cranial fossa beneath the tentorium cerebelli. Its position in the hindbrain is posterior to both pons and medulla oblongata. It is connected to the midbrain through superior cerebellar peduncles, to the pons through middle cerebellar peduncles and to the medulla through inferior cerebellar peduncles.
The cerebellum is composed of two hemispheres, which are connected by a median part called the vermis. The surface layer of each cerebellar hemisphere is called the cortex (composed of gray matter). In addition, certain masses of gray matter are found in the interior of the cerebellum and form various nuclei.
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. This occurs through three openings in the roof: one foramen of magendie and two foramina of Luschka.