Septum pellucidum
A thin, vertical, two-layered partition in the brain's midline that separates the front horns of the two lateral ventricles.
At a glance
- English
- Septum pellucidum
- Latin (TA2)
- Septum pellucidum
- System
- Brain and spinal cord
- Region
- Head
- Side
- Single, on the midline
About the septum pellucidum
Its Latin name means translucent wall, and the septum pellucidum is indeed a thin, three-cornered sheet, stretched in the midline between the corpus callosum and the fornix. Its upper and front borders are attached to the underside of the trunk, genu and rostrum of the corpus callosum; its lower back border is attached to the body and columns of the fornix. Each side of it forms the medial wall of the anterior horn and central part of a lateral ventricle, so it divides the two ventricles from each other.
It is made of two thin laminae, each containing some grey matter, nerve fibres and glia, and lined on its ventricular face by ependyma. Its lower part merges with the septal area, where the septal nuclei lie. Small septal veins run across its surfaces towards the interventricular foramen to join the internal cerebral veins, and they are useful landmarks for neurosurgeons and radiologists.
In the fetus a fluid-filled cleft separates the two laminae. This cave of the septum pellucidum normally closes in the months after birth, but it persists in some adults as a slit seen on scans, usually of no consequence. It was once called the fifth ventricle, though it is not part of the ventricular system and does not normally communicate with it; that name is now used instead for the terminal ventricle in the conus of the spinal cord. When the cave extends back behind the columns of the fornix the posterior part is called the cavum vergae.
The septum is absent in septo-optic dysplasia, a developmental disorder that combines underdevelopment of the optic nerves with pituitary hormone deficiency, and it may be missing in holoprosencephaly and severe hydrocephalus. A shift of the septum away from the midline on CT or MRI is a quick sign of a mass pushing the brain across.
Function and supply
- Function
- Separates the anterior horns and central parts of the two lateral ventricles and carries small veins and fibres between the corpus callosum and fornix.
- Blood supply
- Small branches of the anterior cerebral and anterior communicating arteries; drained by the septal veins to the internal cerebral veins.
Anthromica
See the septum pellucidum where it really sits, with every layer of the body around it.
- Every layer, one body. Peel from muscle to bone, nerve, vessel and organ, and turn it any way.
- English and Latin. Every structure named the way your exam names it.
- Quiz until it sticks. Short drills on the structures you keep missing.
Free to start. No card.
