The fourth ventricle is one of the four connected fluid-filled cavities within the

human brain The human brain is the central organ (anatomy), organ of the nervous system, and with the spinal cord, comprises the central nervous system. It consists of the cerebrum, the brainstem and the cerebellum. The brain controls most of the activi ...

. 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 (''aqueduct of Sylvius'') to the obex, and is filled with cerebrospinal fluid (CSF). The fourth ventricle has a characteristic diamond shape in cross-sections of the human brain. It is located within the pons or in the upper part of the medulla oblongata. CSF entering the fourth ventricle through the cerebral aqueduct can exit to the subarachnoid space of the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

through two lateral apertures and a single, midline median aperture.

Boundaries

Fourth Ventricle in the Human Cerebellum

The fourth ventricle has a

roof A roof (: roofs or rooves) is the top covering of a building, including all materials and constructions necessary to support it on the walls of the building or on uprights, providing protection against rain, snow, sunlight, extremes of tempera ...

at its ''upper'' (posterior) surface and a floor at its ''lower'' (anterior) surface, and side walls formed by the cerebellar peduncles (nerve bundles joining the structure on the posterior side of the ventricle to the structures on the anterior side). The caudal tip of the fourth ventricle - where it becomes the central canal - is known as the obex; the obex is also a marker for the level of the foramen magnum of the skull and therefore is a marker for the imaginary dividing line between the medulla and

. The superior portion of the ''roof'' (i.e. of the posterior edge) is formed, in the midline, by a thin lamina called the superior medullary velum, and laterally by the cerebellar peduncles. The inferior portion of the ''roof'' is formed superiorly by the inferior medullary veli and the vermis of the

Cerebellum The cerebellum (: cerebella or cerebellums; Latin for 'little brain') is a major feature of the hindbrain of all vertebrates. Although usually smaller than the cerebrum, in some animals such as the mormyrid fishes it may be as large as it or eve ...

(covered with

choroid plexus The choroid plexus, or plica choroidea, is a plexus of cells that arises from the tela choroidea in each of the ventricles of the brain. Regions of the choroid plexus produce and secrete most of the cerebrospinal fluid (CSF) of the central ...

), and inferiorly by the tela. The inferior portion of the ''roof'' is where CSF can escape the ventricle through three openings: Near each of the three corners of the inferior roof there is an opening into the cisterna magna, the caudal opening being the '' foramen Magendie'', while the lateral openings are the '' foramina of Luschka''. Therefore, the fourth ventricle is the connector between the ventricular system (where CSF is produced) and the subarachnoid space (where CSF is absorbed). The ''roof'' rises (i.e. posteriorly) to a peak, known as the fastigium (Latin for "summit"); the fastigial nucleus lies immediately above the roof of the fourth ventricle, in the cerebellum. The ''floor'' (i.e. the anterior edge) of the fourth ventricle constitutes the rhomboid fossa, and comprises a number of general features. A sulcus - the median sulcus - extends the length of the ventricle (from the cerebral aqueduct of the midbrain to the central canal of the spinal cord), dividing the floor into right and left halves. Each half is further divided by a further sulcus - the sulcus limitans - along a line parallel to the median sulcus; within the floor, motor neurons are located medially of the sulcus limitans, while sensory neurons are located laterally. The elevation between the median sulcus and sulcus limitans (i.e. the region for motor neurons), is known as the '' medial eminence'', while the lateral region (i.e. that for the sensory neurons) is known as the ''vestibular area''. The sulcus limitans bifurcates at either end - the ''superior fovea'' cerebrally, and the ''inferior fovea'' caudally. The pons is located behind the middle and superior portion of the ''floor''. In the superior region of the pons is the locus coeruleus, which due to its concentration of noradrenaline has a

sky blue Sky blue refers to a collection of shades comparable to that of a clear daytime sky. Typically it is a shade of cyan or light teal, though some iterations are closer to light Azure (color), azure or light blue. The term (as "sky blew") is atte ...

appearance, visible (in a colour closer to teal) through the floor of the ventricle, superiorly to the superior fovea. The internal part of the

facial nerve The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of ta ...

bulges into the ventricle, forming the facial colliculus, in the process of looping around the abducens nucleus within the inferior region of the Pons. The medulla oblongata is located behind the inferior portion of the ''floor'' (and continues caudally of the ventricle). Medullary striae emerge via the median sulcus and run transversely across the floor to become part of the

inferior cerebellar peduncle The inferior cerebellar peduncle is formed by fibers of the restiform body that join with fibers from the much smaller juxtarestiform body. The inferior cerebellar peduncle is the smallest of the three cerebellar peduncles. The upper part of t ...

. The hypoglossal nucleus bulges into the ''floor'', creating the hypoglossal trigone, located slightly superiorly to the inferior fovea, within the median eminence. The dorsal nucleus of vagus nerve, within the medulla oblongata, comprises cells that are spindle shaped, also creating a bulge—the vagal trigone—in the region of the ''floor'' which overlies them; this is the region inferior of the inferior fovea.

Development

The ventricular system including the fourth ventricle, develops from the central canal of the neural tube. Specifically, the fourth ventricle originates from the portion of the tube that is present in the developing rhombencephalon. During the first trimester of pregnancy the central canal expands into the lateral, third and fourth ventricles, connected by thinner channels.

Choroid plexus The choroid plexus, or plica choroidea, is a plexus of cells that arises from the tela choroidea in each of the ventricles of the brain. Regions of the choroid plexus produce and secrete most of the cerebrospinal fluid (CSF) of the central ...

es appear in the ventricles which produce cerebrospinal fluid. If the flow of fluid is blocked ventricles may become enlarged and cause hydrocephalus.

Clinical significance

The floor of the fourth ventricle is a common location of an

intracranial The cranial cavity, also known as intracranial space, is the space within the skull that accommodates the brain. The skull is also known as the cranium. The cranial cavity is formed by eight cranial bones known as the neurocranium that in human ...

ependymoma in children.

Additional images

File:Gray695.png, Transverse section of medulla oblongata below the middle of the olive. File:Gray708.svg, Scheme of roof of fourth ventricle. File:Gray709.png, Rhomboid fossa. File:Gray720.png, Median sagittal section of brain. File:Gray736.png, Drawing of a cast of the ventricular cavities, viewed from the side. File:Gray768.png, Diagram showing the positions of the three principal subarachnoid cisternæ. File:Slide6qq.JPG, Fourth ventricle

References

External links

* - "Fourth Ventricle, Sagittal Section, Medial View" * * {{Authority control Brainstem Ventricular system de:Hirnventrikel#Vierter Ventrikel