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

human brain The human brain is the central organ of the human nervous system, and with the spinal cord makes up the central nervous system. The brain consists of the cerebrum, the brainstem and the cerebellum. It controls most of the activities of ...

. These cavities, known collectively as the

ventricular system The ventricular system is a set of four interconnected cavities known as cerebral ventricles in the brain. Within each ventricle is a region of choroid plexus which produces the circulating cerebrospinal fluid (CSF). The ventricular system is co ...

, consist of the left and right lateral ventricles, the

third ventricle The third ventricle is one of the four connected ventricles of the ventricular system within the mammalian brain. It is a slit-like cavity formed in the diencephalon between the two thalami, in the midline between the right and left lateral ...

, and the fourth ventricle. The fourth ventricle extends from the

cerebral aqueduct The cerebral aqueduct (aqueductus mesencephali, mesencephalic duct, sylvian aqueduct or aqueduct of Sylvius) is a conduit for cerebrospinal fluid (CSF) that connects the third ventricle to the fourth ventricle of the ventricular system of the br ...

(''aqueduct of Sylvius'') to the

obex OBEX (abbreviation of OBject EXchange, also termed IrOBEX) is a communications protocol that facilitates the exchange of binary objects between devices. It is maintained by the Infrared Data Association but has also been adopted by the Bluetooth S ...

, and is filled with

cerebrospinal fluid Cerebrospinal fluid (CSF) is a clear, colorless body fluid found within the tissue that surrounds the brain and spinal cord of all vertebrates. CSF is produced by specialised ependymal cells in the choroid plexus of the ventricles of the ...

(CSF). The fourth ventricle has a characteristic diamond shape in cross-sections of the human brain. It is located within the

pons The pons (from Latin , "bridge") is part of the brainstem that in humans and other bipeds lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum. The pons is also called the pons Varolii ("bridge of Va ...

or in the upper part of the

medulla oblongata 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 (invol ...

. CSF entering the fourth ventricle through the cerebral aqueduct can exit to the

subarachnoid space In anatomy, the meninges (, ''singular:'' meninx ( or ), ) are the three membranes that envelop the brain and spinal cord. In mammals, the meninges are the dura mater, the arachnoid mater, and the pia mater. Cerebrospinal fluid is located in ...

of the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...

through two

lateral apertures The lateral aperture is a paired structure in human anatomy. It is an opening in each lateral extremity of the lateral recess of the fourth ventricle of the human brain, which also has a single median aperture. The two lateral apertures provide ...

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 t ...

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 The central canal (also known as spinal foramen or ependymal canal) is the cerebrospinal fluid-filled space that runs through the spinal cord. The central canal lies below and is connected to the ventricular system of the brain, from which it ...

- is known as the

; the obex is also a marker for the level of the

foramen magnum The foramen magnum ( la, great hole) is a large, oval-shaped opening in the occipital bone of the skull. It is one of the several oval or circular openings (foramina) in the base of the skull. The spinal cord, an extension of the medulla oblon ...

of the

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

and therefore is a marker for the imaginary dividing line between the

medulla Medulla or Medullary may refer to: Science * Medulla oblongata, a part of the brain stem * Renal medulla, a part of the kidney * Adrenal medulla, a part of the adrenal gland * Medulla of ovary, a stroma in the center of the ovary * Medulla of t ...

and

The superior portion of the ''roof'' (i.e. of the posterior edge) is a thin lamina - the

superior medullary velum The superior medullary velum (anterior medullary velum) is a thin, transparent lamina of white matter, which stretches between the superior cerebellar peduncles; on the dorsal surface of its lower half the folia and lingula are prolonged. It fo ...

- connecting the left and right superior cerebellar peduncles together. The inferior portion of the ''roof'' - the

inferior medullary velum The inferior medullary velum (posterior 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. So ...

- has a tricorn cross section, directed caudally and laterally, and is formed by the

Cerebellum The cerebellum (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 or even larger. In humans, the cerebe ...

directly. Near each of the 3 corners of the inferior roof is an opening into the

cisterna magna The cisterna magna (or cerebellomedullar cistern) is one of three principal openings in the subarachnoid space between the arachnoid and pia mater layers of the meninges surrounding the brain. The openings are collectively referred to as the su ...

, the caudal opening being the '' foramen Magendie'', while the lateral openings are the '' foramina of Luschka''. The ''roof'' rises (i.e. posteriorly) to a peak, known as the fastigium (Latin for "summit"); the

fastigial nucleus The fastigial nucleus is located in the cerebellum. It is one of the four deep cerebellar nuclei (the others being the nucleus dentatus, nucleus emboliformis and nucleus globosus), and is grey matter embedded in the white matter of the cereb ...

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 The rhomboid fossa is a rhombus-shaped depression that is the anterior part of the fourth ventricle. Its anterior wall, formed by the back of the pons and the medulla oblongata, constitutes the floor of the fourth ventricle. It is covered by a th ...

, and comprises a number of general features. A sulcus - the median sulcus - extends the length of the ventricle (from the

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 In the human brain, the rhomboid fossa is divided into symmetrical halves by a median sulcus which reaches from the upper to the lower angles of the fossa and is deeper below than above. On either side of this sulcus is an elevation, the medial em ...

'', 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

is located behind the middle and superior portion of the ''floor''. In the superior region of the pons is the

locus coeruleus The locus coeruleus () (LC), also spelled locus caeruleus or locus ceruleus, is a nucleus in the pons of the brainstem involved with physiological responses to stress and panic. It is a part of the reticular activating system. The locus coer ...

, which due to its concentration of

noradrenaline Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as both a hormone and neurotransmitter. The name "noradrenaline" (from Latin '' ad'', ...

has a

sky blue Sky blue is a shade of light blue comparable to that of a clear daytime sky. The term (as "sky blew") is attested from 1681. A 1585 translation of Nicolas de Nicolay's 1576 ''Les navigations, peregrinations et voyages faicts en la Turquie'' i ...

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 taste ...

bulges into the ventricle, forming the

facial colliculus The facial colliculus is an elevated area located in the pontine tegmentum (dorsal pons), within the floor of the fourth ventricle (i.e. the rhomboid fossa). It is formed by fibres from the facial motor nucleus looping over the abducens nucleus. ...

, in the process of looping around the

abducens nucleus The abducens nucleus is the originating nucleus from which the abducens nerve (VI) emerges—a cranial nerve nucleus. This nucleus is located beneath the fourth ventricle in the caudal portion of the pons, medial to the sulcus limitans. The abd ...

within the inferior region of the Pons. The

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 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 nerv ...

. 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

of the neural tube. Specifically, the fourth ventricle originates from the portion of the tube that is present in the developing

rhombencephalon The hindbrain or rhombencephalon or lower brain 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. Metencephal ...

. 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 nerv ...

es appear in the ventricles which produce

. If the flow of fluid is blocked ventricles may become enlarged and cause

hydrocephalus Hydrocephalus is a condition in which an accumulation of cerebrospinal fluid (CSF) occurs within the brain. This typically causes increased pressure inside the skull. Older people may have headaches, double vision, poor balance, urinary i ...

Clinical significance

The fourth ventricle is a common location of an intracranial

ependymoma An ependymoma is a tumor that arises from the ependyma, a tissue of the central nervous system. Usually, in pediatric cases the location is intracranial, while in adults it is spinal. The common location of intracranial ependymomas is the fourth ...

l tumour.

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