Development of the Diencephalon/Telencephalon (4th of 10)
The lamina terminalis (represents the membrane formed at the point of closure of the anterior neuropore) is the most rostral structure of the early telencephalon. By 10 weeks it contains the rudiments of the commissural bundles i.e., corpus callosum, optic chiasm and anterior commissure. The lamina terminalis provides the only location where nerves interconnect the cerebral hemispheres. Crossing fibers of the optic chiasm develop in the lamina ventrally, the anterior commissure connects olfactory bulbs and temporal lobes, the commissure of the fornix joins the hippocampal formations, and most dorsally is the corpus callosum which connects non-olfactory cortical areas. Other crossing fibers do not connect the hemispheres e.g., the posterior commissure connects preoptic areas, the habenular commissure connects habenular nuclei.
The interventricular foramina, which connects the 3rd ventricle with the lateral ventricles, lies just caudal to the lamina terminalis.). The stria medullaris and tela choroidea form the roof of the 3rd ventricle.