Identify the structure marked by a red arrow in the given image:
A. Great vein of galen
B. Pineal gland
D. Falx cerebri
Answer C. Fornix
- The fornix is the main efferent system of the hippocampus and an important part of the limbic system.
- It is one of the commissural fibers connecting the cerebral hemispheres.
- Roughly C-shaped, the fornix extends from the hippocampus to the mammillary bodies of the hypothalamus and the anterior nuclei of the thalamus.
- It is a curvilinear bundle of white matter fibers that begins as a group of myelinated fibers called the alveus.
- The alveus joins to form the fimbria of the hippocampus.
- The fimbria of each hippocampus thickens and then splits off from the hippocampus to form the crus (leg) of the fornix.
The fornix is composed of four parts:
- crura: best seen at the splenium of the corpus callosum at the level of the superior colliculus on coronal images
- commissure: connects the crura
- body: from the merging of the crura, provides one of two major paths through which the hippocampus communicate with each other
- columns (anterior pillars): curves anteriorly and dives into the hypothalamus (mammillary bodies)