Fourth ventricle
Encyclopedia
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 (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
. CSF entering the fourth ventricle through the cerebral aqueduct can exit to the subarachnoid space
of the spinal cord
through two lateral foramina of Luschka (singular: foramen of Luschka) and a single, midline foramen of Magendie
(see List of human anatomical parts named after people).
and a "floor" ventrally. The roof of the fourth ventricle is formed by the cerebellum
(superior and inferior medullary vela), the floor by the rhomboid fossa
, and the side "walls" formed by the cerebellar peduncles. Among the prominent features of the floor of the fourth ventricle are the:
. If its production is bigger than resorption or its circulation is blocked- the enlargement of the ventricles may appear and cause a hydrocephalus
. Fetal lateral ventricles may be diagnosed using linear or planar measurements. See also Dandy-Walker syndrome
.
Brain
The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
. These cavities, known collectively as the ventricular system
Ventricular system
The ventricular system is a set of structures containing cerebrospinal fluid in the brain. It is continuous with the central canal of the spinal cord.-Components:The system comprises four ventricles:* right and left lateral ventricles* third ventricle...
, consist of the left and right lateral ventricles, the third ventricle
Third ventricle
The third ventricle is one of four connected fluid-filled cavities comprising the ventricular system within the human brain. It is a median cleft between the two thalami, and is filled with cerebrospinal fluid ....
, and the fourth ventricle. The fourth ventricle extends from the cerebral aqueduct (aqueduct of Sylvius) to the obex
Obex
The obex is the point in the human brain at which the fourth ventricle narrows to become the central canal of the spinal cord.The obex occurs in the caudal medulla.The decussating of sensory fibers happens at this point....
, and is filled with cerebrospinal fluid
Cerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
(CSF).
The fourth ventricle has a characteristic diamond shape in cross-sections of the human brain. It is located within the pons
Pons
The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...
or in the upper part of the medulla
Medulla oblongata
The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...
. CSF entering the fourth ventricle through the cerebral aqueduct can exit to the subarachnoid space
Subarachnoid space
In the central nervous system, the subarachnoid cavity is the interval between the arachnoid membrane and pia mater....
of the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
through two lateral foramina of Luschka (singular: foramen of Luschka) and a single, midline foramen of Magendie
Median aperture
The median aperture drains CSF from the fourth ventricle into the cisterna magna. The two lateral apertures , one on the left and one on the right, are the primary routes for drainage of cerebrospinal fluid from the fourth ventricle into the cerebellopontine angle cistern...
(see List of human anatomical parts named after people).
Roof and floor
The fourth ventricle has a "roof" dorsallyAnatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
and a "floor" ventrally. The roof of the fourth ventricle is formed by the cerebellum
Cerebellum
The cerebellum is a region of the brain that plays an important role in motor control. It may also be involved in some cognitive functions such as attention and language, and in regulating fear and pleasure responses, but its movement-related functions are the most solidly established...
(superior and inferior medullary vela), the floor by the rhomboid fossa
Rhomboid fossa
The anterior part of the fourth ventricle is named, from its shape, the rhomboid fossa, and its anterior wall, formed by the back of the pons and medulla oblongata, constitutes the floor of the fourth ventricle....
, and the side "walls" formed by the cerebellar peduncles. Among the prominent features of the floor of the fourth ventricle are the:
- facial colliculusFacial colliculusThe facial colliculus is an elevated area located on the dorsal pons. In the floor of the 4th ventricle It is formed by motor fibers of the facial nerve as they loop over the abducens nucleus...
: formed by the internal part of the facial nerveFacial nerveThe facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
as it loops around the abducens nucleusAbducens nucleusThe abducens nucleus is the originating nucleus from which the abducens nerve 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....
in the lower ponsPonsThe pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...
; - sulcus limitansSulcus limitansIn the floor of the fourth ventricle, the sulcus limitans separates the cranial nerve motor nuclei from the sensory nuclei . In the superior part of the rhomboid fossa, it corresponds with the lateral limit of the fossa and presents a bluish-gray area, the locus ceruleus In the floor of the fourth...
: which represents the border between the alar plateAlar plateThe alar plate is a neural structure in the embryonic nervous system, part of the dorsal side of neural tube, that involves the communication of general somatic and general visceral sensory impulses. The caudal part later becomes sensory axon part of the spinal cord.-External links:* *...
and the basal plateBasal plateBasal plate may refer to:* Basal plate , the region of the neural tube ventral to the sulcus limitans* Basal plate , between this plate and the uterine muscular fibres are the stratum spongiosum and the boundary layer...
of the developing neural tubeNeural tubeIn the developing vertebrate, the neural tube is the embryo's precursor to the central nervous system, which comprises the brain and spinal cord...
; - obexObexThe obex is the point in the human brain at which the fourth ventricle narrows to become the central canal of the spinal cord.The obex occurs in the caudal medulla.The decussating of sensory fibers happens at this point....
: represents the caudal tip of the fourth ventricle; the obex is also a marker for the level of the foramen magnum of the skullHuman skullThe human skull is a bony structure, skeleton, that is in the human head and which supports the structures of the face and forms a cavity for the brain.In humans, the adult skull is normally made up of 22 bones...
and therefore is a marker for the imaginary dividing line between the medullaMedulla oblongataThe medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...
and spinal cordSpinal cordThe spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
. - "median sulcus" - divides the floor in to right and left halves.It extends from cerebral aqueduct of the midbrain to central canal of the spinal cord.
- "stria medullaris" - fibers derived from arcuare nuclei ,which emerge from the median sulcus and run transversely across the floor to enter into the inferior cerebral penducle.
- "medial eminence" - elevations on either side of the median sulcus.
- "sulcus limitans" - medial eminance is laterally bounded by sulcus limitans.
- "vestibular area" - lateral to sulcus limitans vestibular nuclei is overlied by this .
- The upper end of the sulcus limitans widens into a triangular depression called "suprior fovea" above suprior fovea sulcus limitans presents a flattend grey area called "locus cerulus".
- The lower end of the sulcus limitans widens into a triangular depression called "Inferior fovea".
- Other features are the Hypoglossal triangle and vagal triangle.
Development
The fourth ventricle, similarly to other parts of the ventricular system of the brain, 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 central canal expands into lateral, third and fourth ventricles, connected by thinner channels. In lateral ventricles specialized areas- choroid plexuses appear, which produce cerebrospinal fluidCerebrospinal fluid
Cerebrospinal fluid , Liquor cerebrospinalis, is a clear, colorless, bodily fluid, that occupies the subarachnoid space and the ventricular system around and inside the brain and spinal cord...
. If its production is bigger than resorption or its circulation is blocked- the enlargement of the ventricles may appear and cause a hydrocephalus
Hydrocephalus
Hydrocephalus , also known as "water in the brain," is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid in the ventricles, or cavities, of the brain. This may cause increased intracranial pressure inside the skull and progressive enlargement of the head,...
. Fetal lateral ventricles may be diagnosed using linear or planar measurements. See also Dandy-Walker syndrome
Dandy-Walker syndrome
Dandy–Walker syndrome , or Dandy–Walker complex, is a congenital brain malformation involving the cerebellum and the fluid filled spaces around it. A key feature of this syndrome is the partial or even complete absence of the part of the brain located between the two cerebellar hemispheres...
.