QS Study

The corpus callosum, also known as the colossal commissure, is a wide, flat bundle of neural fibres beneath the cortex in the eutherian brain at the longitudinal fissure. It is the primary commissural region of the brain consisting of white matter tracts that connect the left and right cerebral hemispheres. This neural tissue facilitates communication between the two sides of the brain.

Fibres present in the corpus callosum

It is composed of approximately 200 million heavily myelinated nerve fibres that form homotopic or heterotopic projections to contralateral neurons in the same anatomical layer. The neurons in the corpus callosum also are insulated by a myelin sheath, which facilitates the rapid conduction of electrical impulses between the hemispheres.

  • The rostrum connects the orbital surfaces of the two frontal lobes.
  • The forceps minor is made up of fibres of the genu that connect the two frontal lobes.
  • The forceps major is made up of fibres of the splenium connecting the two occipital lobes.
  • The tapetum is formed by the fibres from the trunk & splenium of the corpus callosum.
  • It is the largest white matter structure in the human brain, consisting of 200–250 million axonal projections.
  • The body or truncus of the corpus callosum is between the splenium and the genu. A narrowed part between the body and the splenium is known as the isthmus of the corpus callosum.

Fibers present in corpus callosum 1

Fig: Focal lesion in the splenium of the corpus callosum for a 10-year-old boy with TBI on conventional T1-weighted MRI midsagittal image.

Anatomically from anterior to posterior, the corpus callosum is composed of four parts based on previous histological findings: the rostrum, genu, body, and splenium, each responsible for connecting distinct areas of the cortex. It has played an important role in the elucidation of functions specific to each of the cerebral hemispheres.

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