The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (involuntary) functions, ranging from vomiting to sneezing. The medulla contains the cardiac, respiratory, vomiting and vasomotor centers, and therefore deals with the autonomic functions of breathing, heart rate and blood pressure as well as the sleep–wake cycle.
The brainstem is the stalk-like part of the brain that interconnects the cerebrum and diencephalon with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is continuous with the thalamus of the diencephalon through the tentorial notch.
The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle. The fourth ventricle extends from the cerebral aqueduct to the obex, and is filled with cerebrospinal fluid (CSF).
The lateral ventricles are the two largest ventricles of the brain and contain cerebrospinal fluid (CSF). Each cerebral hemisphere contains a lateral ventricle, known as the left or right lateral ventricle, respectively.
The posterior cranial fossa is the part of the cranial cavity located between the foramen magnum, and tentorium cerebelli. It is formed by the sphenoid bones, temporal bones, and occipital bone. It lodges the cerebellum, and parts of the brainstem.
The upper part of the posterior district of the medulla oblongata is occupied by the inferior cerebellar peduncle, a thick rope-like strand situated between the lower part of the fourth ventricle and the roots of the glossopharyngeal and vagus nerves.
The fastigial nucleus is located in the cerebellum. It is one of the four deep cerebellar nuclei, and is grey matter embedded in the white matter of the cerebellum.
The posterior inferior cerebellar artery (PICA) is the largest branch of the vertebral artery. It is one of the three main arteries that supply blood to the cerebellum, a part of the brain. Blockage of the posterior inferior cerebellar artery can result in a type of stroke called lateral medullary syndrome.
The superior cerebellar artery (SCA) is an artery of the head. It arises near the end of the basilar artery. It is a branch of the basilar artery. It supplies parts of the cerebellum, the midbrain, and other nearby structures. It is the cause of trigeminal neuralgia in some patients.
Cerebellar peduncles connect the cerebellum to the brain stem. There are six cerebellar peduncles in total, three on each side:
Winding around the inferior cerebellar peduncle in the lower part of the fourth ventricle, and crossing the area acustica and the medial eminence are a number of white strands, the medullary striae, which form a portion of the cochlear division of the vestibulocochlear nerve and disappear into the median sulcus. Stria medullaris are axons of arcuate neurons. Courses in the floor of the fourth ventricle. Joins the restiform body to reach the cerebellum.
In the human brain, the superior cerebellar peduncle is a paired structure of white matter that connects the cerebellum to the midbrain. It consists mainly of efferent fibers, the cerebellothalamic tract that runs from a cerebellar hemisphere to the contralateral thalamus, and the cerebellorubral tract that runs from a cerebellar hemisphere to the red nucleus. It also contains afferent tracts, most prominent of which is the ventral spinocerebellar tract. Other afferent tracts are the trigeminothalamic fibers, tectocerebellar fibers, and noradrenergic fibers from the locus coeruleus. The superior peduncle emerges from the upper and medial parts of the white matter of each hemisphere and is placed under cover of the upper part of the cerebellum.
The middle cerebellar peduncle is a paired structure of the brain. It connects the pons to the cerebellum, with fibres originating from the pontine nucleus and travelling to the opposite hemisphere of the cerebellar cortex. It is supplied by the anterior inferior cerebellar artery (AICA) and branches from the basilar artery. It conveys information from the cerebrum and the pons to the cerebellum.
The tela choroidea is a region of meningeal pia mater that adheres to the underlying ependyma, and gives rise to the choroid plexus in each of the brain’s four ventricles. Tela is Latin for woven and is used to describe a web-like membrane or layer. The tela choroidea is a very thin part of the loose connective tissue of pia mater overlying and closely adhering to the ependyma. It has a rich blood supply. The ependyma and vascular pia mater – the tela choroidea, form regions of minute projections known as a choroid plexus that projects into each ventricle. The choroid plexus produces most of the cerebrospinal fluid of the central nervous system that circulates through the ventricles of the brain, the central canal of the spinal cord, and the subarachnoid space. The tela choroidea in the ventricles forms from different parts of the roof plate in the development of the embryo.
The superior medullary velum is a thin, transparent lamina of white matter which - together with the inferior medullary velum - forms the roof of the fourth ventricle. It extends between the two superior cerebellar peduncles. The lingula of cerebellum covers - and adheres to - its dorsal surface.
The cerebellar tonsil is a rounded lobule on the undersurface of each cerebellar hemisphere, continuous medially with the uvula of the cerebellar vermis and superiorly by the flocculonodular lobe. Synonyms include: tonsilla cerebelli, amygdala cerebelli, the latter of which is not to be confused with the cerebral tonsils or amygdala nuclei located deep within the medial temporal lobes of the cerebral cortex.
The inferior medullary velum is a thin layer of white substance, prolonged from the white center of the cerebellum, above and on either side of the nodule; it forms the infero-posterior part of the fourth ventricle.
The superior cistern is a dilation as a subarachnoid cistern of the subarachnoid space around the brain. It lies between the splenium of the corpus callosum and the superior surface of the cerebellum. It extends between the layers of the tela choroidea of the third ventricle. It contains the great cerebral vein, posterior cerebral artery, quadrigeminal artery, glossopharyngeal nerve, and the pineal gland.
The nodule, or anterior end of the inferior vermis, abuts against the roof of the fourth ventricle, and can only be distinctly seen after the cerebellum has been separated from the medulla oblongata and pons.
The anatomy of the cerebellum can be viewed at three levels. 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 in the middle. At the intermediate level, the cerebellum and its auxiliary structures can be broken down into several hundred or thousand independently functioning modules or compartments known as microzones. At the microscopic level, each module consists of the same small set of neuronal elements, laid out with a highly stereotyped geometry.
