The pineal body makes its first appearance in man at about the second fetal month as a cellular mass and an evagination in the roof of the diencephalon. The two structures fuse, and the cavity of the united mass deepens to form the pineal recess. The cells lining the recess develop cilia and come to resemble the ependyma closely. The histogenesis of the pineal body itself is complicated, but the parenchymal cells seem to develop from ependymal anlages. Several facts support this opinion, in particular the occurrence of tubules in the fetal pineal body and the possession of blepharoplasts and processes by pineal cells. At about the sixth fetal month, masses of small, darkly staining cells, thought by Globus and Silbert,1 Bailey2 and others to be mesenchymal in origin, appear in the pineal body in conjunction with connective tissue and blood vessels. These smaller cells form a mosaic
Mackay RP. PINEALOMA OF DIFFUSE EPENDYMAL ORIGIN. Arch NeurPsych. 1939;42(5):892–902. doi:https://doi.org/10.1001/archneurpsyc.1939.02270230114009
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