Fourth Ventricle
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Fourth Ventricle
Fourth ventricle
Gray734.png
Scheme showing relations of the ventricles to the surface of the brain. (Fourth ventricle labeled at bottom center.)
Gray735.png
Drawing of a cast of the ventricular cavities, viewed from above. (Fourth ventricle visible at bottom center.)
Details
Identifiers
Latin ventriculus quartus
MeSH D020546
NeuroNames 621
NeuroLex ID birnlex_1256
TA A14.1.05.701
FMA 78469
Anatomical terms of neuroanatomy

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 apertures and a single, midline median aperture.

Roof and floor

Fourth ventricle location shown in blue, pons shown in green

The fourth ventricle has a roof at its upper surface and a floor at its lower surface, and side walls formed by the cerebellar peduncles. The roof is formed by the cerebellum (superior and inferior medullary vela). The fastigium, (Latin for "summit"), is used to refer to the peak of the fourth ventricle.[1] The fastigial nucleus lies immediately above the roof of the fourth ventricle, in the cerebellum.

The floor of the fourth ventricle is formed by the rhomboid fossa. Its features include:

  • the facial colliculus: formed by the internal part of the facial nerve as it loops around the abducens nucleus in the lower pons
  • the sulcus limitans: separates the motor nuclei from the sensory nuclei, and gives a lateral boundary to the medial eminence
  • the obex: represents the caudal tip of the fourth ventricle; 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 spinal cord
  • the median sulcus - divides the floor into right and left halves. It extends from cerebral aqueduct of the midbrain to central canal of the spinal cord
  • the medullary striae - fibers derived from arcuate nuclei, which emerge from the median sulcus and run transversely across the floor to enter into the inferior cerebellar peduncle
  • the medial eminence - elevations on either side of the median sulcus
  • the "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 "superior fovea". Above the superior fovea sulcus, the sulcus limitans presents a flattened grey nucleus called the locus coeruleus
  • the lower end of the sulcus limitans widens into a triangular depression called the "inferior fovea"
  • other features are the hypoglossal trigone and the vagal trigone

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.[2] During the first trimester of pregnancy the central canal expands into the lateral, third and fourth ventricles, connected by thinner channels.[3]Choroid plexuses 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 fourth ventricle is a common location of an intracranial ependymomal tumour.

Additional images

References

  1. ^ Dr. M. A. (Toby) Arnold. "Anatomy Glossary". 
  2. ^ Le, Tao; Bhushan, Vikas; Vasan, Neil (2010). First Aid for the USMLE Step 1: 2010 20th Anniversary Edition. USA: The McGraw-Hill Companies, Inc. p. 126. ISBN 978-0-07-163340-6. 
  3. ^ Carlson, Bruce M. (1999). Human Embryology & Developmental Biology. Mosby. pp. 237-238. ISBN 0-8151-1458-3. 

External links


  This article uses material from the Wikipedia page available here. It is released under the Creative Commons Attribution-Share-Alike License 3.0.

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