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Parts of corpus callosum

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corpus callosum parts anatomy diagram

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Here is a complete, textbook-sourced overview of the parts of the corpus callosum.

Parts of the Corpus Callosum

The corpus callosum is the largest fiber bundle in the brain, containing roughly 300 million axons that interconnect the two cerebral hemispheres. It is divided into 4 main parts (anterior to posterior):
Medial view of the right cerebral hemisphere showing all parts of the corpus callosum - CC_g (genu), CC_r (rostrum), CC_b (body), CC_i (isthmus), CC_s (splenium)
Medial view of the right cerebral hemisphere (Kaplan & Sadock's Comprehensive Textbook of Psychiatry)

1. Rostrum (CC_r)

  • The most anterior-inferior portion, projecting backward from the genu
  • Thin and hook-like, it forms the inferior bend of the structure
  • Connects orbitofrontal cortex regions between hemispheres

2. Genu (CC_g)

  • The anterior knee (genu = Latin for "knee")
  • Curves anteriorly and dorsally from the rostrum
  • Fibers from the genu form the forceps minor, connecting the prefrontal cortices
  • Carries higher-order cognitive information from the prefrontal cortex

3. Body (Trunk) (CC_b)

  • The largest and longest part, running in the mid-sagittal plane
  • Connects the motor, somatosensory, auditory, and association cortices
  • Carries predominantly visual, auditory, and somatosensory information

4. Splenium (CC_s)

  • The enlarged, rounded posterior end - the thickest part
  • Fibers form the forceps major, connecting the occipital cortices
  • Carries higher-order sensory and parietal/temporal cortex connections
  • Last part to develop embryologically

The Isthmus (CC_i)

  • A narrow constriction between the body and the splenium
  • Sometimes listed as a 5th subdivision (especially in neuroimaging/neuropsychiatry texts)
  • Carries connections between the temporal and parietal cortices

Fiber Projections Summary

PartCortex ConnectedInformation Carried
RostrumOrbitofrontalLimbic/prefrontal
GenuPrefrontalHigher-order cognition
BodyMotor, somatosensory, auditoryMotor, sensory, auditory
IsthmusPosterior parietal, superior temporalSomatosensory, auditory
SpleniumOccipital, posterior temporal, parietalVisual, higher-order sensory

Embryological Development

The corpus callosum develops between 7 and 20 weeks' gestation. Development proceeds from the posterior genu and anterior body first, then the anterior genu and rostrum, and finally the splenium (all parts present by ~20 weeks). This order is important clinically: agenesis affecting the genu/body but sparing the splenium suggests acquired destruction rather than developmental failure.
Sources: Kaplan & Sadock's Comprehensive Textbook of Psychiatry (FIGURE 1.2-13); Grainger & Allison's Diagnostic Radiology; Gray's Anatomy for Students
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