A sagittal tissue section of a 7th week embryo (HE stain, 10 × 10). The brain vesicle can be seen, and the base of the diencephalon thickens. Meanwhile, Rathke’s pouch grows into the incrassated diencephalon. A clear acidophilic stained demarcation is showed between them, which is considered to be the pia mater. (1) Diencephalon, (2) Rathke’s pouch, (3) stomodeal, (4) brain vesicle. Arrow: Pia mater
and Embryology Related to Craniopharyngiomas
The pia mater reportedly appears during early neural tube development from glioblasts. Both the arachnoid and the dura mater are differentiated from ectoderm mesenchymal cells. The arachnoid structure can be observed in the 10th week. As the approach of the anterior pituitary and posterior pituitary occurs during the 5th to 7th week of embryogenetic development, the pia mater and several layers of mesenchymal cells should separate Rathke’s pouch and brain tissue (Fig. 1.3). Thus, from the point of view of embryonic development, Rathke’s pouch is located in the outside of the pia mater.