The
septum pellucidum (also called the
septum lucidum) is a thin, triangular, vertical membrane that separates the
lateral ventricles of the
brain. It separates the anterior horn of the left and right lateral ventricles. It runs as a sheet from the corpus callosum down to the
fornix. When the hemispheres are cut apart, the septum remains on one hemisphere, usually the left. The septum pellucidum is currently believed to have no particularly special functional importance.
Layers
The septum pellucidum actually consists of two layers or
laminae of both
white and
gray matter, called the
laminae septi pellucidi.
These layers are normally fused; however, in approximately one-tenth of humans, there is a slit-like cavity between them, referred to as cavum septum pellucidum, cavum septi pellucidi, or "fifth ventricle" . The last term has lost favor in recent years, as the space is usually not continuous with the ventricular system and does not contain cerebrospinal fluid . Indeed fifth ventricle has been used for other purposes in recent years..
Location
The septum pellucidum is located in the midline of the brain, between the two
cerebral hemispheres. It is attached
superiorly (above), anteriorly (in front), and inferiorly (below) to the
corpus callosum, the large collection of nerve fibers that connect the two hemispheres.
Inferiorly and posteriorly (in back), it is attached to the anterior part of the fornix.
On either side are the two lateral ventricles, pockets of cerebrospinal fluid within the cerebral hemispheres.
Pathology
Absence of the septum pellucidum or corpus callosum, caused by
mutations in the
gene, is associated with
septo-optic dysplasia. This may result in
hypothalamic dysfunction and
hypopituitarism, as well as problems of vision, coordination, and intelligence, among other abnormalities.
One famous reference to an abnormality of the septum pellucidum would be the movie Rocky V. In the movie, the main character Rocky Balboa is forced to retire due to brain damage sustained throughout his career.
Additional images
References
- Gray, Henry & Clemente, Carmine D. (1984). Gray's Anatomy of the Human Body (30th ed.). New York: Lippincott Williams & Wilkins.
- Kasper, Dennis L.; Braunwald, Eugene; Fauci, Anthony S.; Hauser, Stephen L.; Longo, Dan L.; Jameson, J. Larry; & Kurt J. Isselbacher, (Eds.) (2004). Harrison's Principles of Internal Medicine (16th ed.). New York: McGraw-Hill.
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