Anatomy of the Corpus Callosum
When studying the brain, the corpus callosum (corpus callosum) is a central landmark. As the largest commissure of the telencephalon, its fibers cross between the hemispheres, ensuring functional and anatomical integration.
Anatomically, the corpus callosum is divided into four sequential parts:
- Rostrum (rostrum) — the tapered anteroinferior portion;
- Genu (genu) — the sharp anterior bend;
- Body (truncus) — the longest central segment;
- Splenium (splenium) — the thickened posterior end.
The fibers composing the corpus callosum radiate outward into the white matter of each hemisphere. Anteriorly, they form the forceps minor (forceps frontalis), connecting the frontal lobes. Posteriorly, they form the forceps major (forceps occipitalis), connecting the occipital lobes.
The superior surface of the corpus callosum is covered by the indusium griseum (indusium griseum), a delicate vestigial layer of gray matter. Within this gray layer, anatomists identify the medial and lateral longitudinal striae (striae longitudinales mediales and striae longitudinales laterales).
Fornix: White Matter Tracts
The fornix (fornix) is a massive, arching white matter tract composed of longitudinally running nerve fibers. Topographically classified as telencephalic white matter, it functions as part of the limbic system.
For descriptive purposes, the fornix is divided into three main parts:
- Columns of the fornix (columnae fornicis) — curving anteriorly and inferiorly;
- Body of the fornix (corpus fornicis) — the central, elevated portion;
- Crura of the fornix (crura fornicis) — diverging posteriorly and inferiorly.
A transverse interhemispheric connection between the right and left fornices is known as the commissure of the fornix (commissura fornicis), which enables communication between symmetrical structures. Inferiorly, the crura continue seamlessly into the fimbria of the hippocampus (fimbria hippocampi).
Hippocampus and Its Topography
The hippocampus (hippocampus) is a prominent curved elevation of gray matter approximately 3 centimeters long, located within the floor of the inferior horn of the lateral ventricle.
The ventricular surface of the hippocampus is covered by a thin layer of white matter termed the alveus of the hippocampus (alveus hippocampi).
Relationships with Other Structures
Medial to the hippocampus lies the fimbria of the hippocampus (fimbria hippocampi), visualized as a prominent white band. As noted earlier, this fimbria is the direct anatomical continuation of the crus of the fornix (crus fornicis).
The anterior end of the hippocampus expands and curves to form the uncus (uncus), which is structurally continuous with the parahippocampal gyrus.