Electron microscopic studies on the problem of photo-sensory and secretory functions of the pineal organ of Lacerta viridis and L muralls

Baumgarten, Hans Georg

Z Anat Entwicklungsgesch: 99-120

1968


Accession: 024601136

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Abstract
The fine structure of the pineal organ was investigated in the lizard L. viridis and L. muralis. There are pinealocytes, supporting cells and basal light cells. Pinealocytes are columnar cells consisting of a supranuclear part which corresponds to the inner segment of photoreceptor cells and a basal part which splits into several basal processes. The inner segment is regularly separated into 2 sections. The distal section protrudes into the pineal lumen, whereas the proximal contains the ellipsoid, a Golgi field, rough endoplasmatic reticulum and 3 types of dense bodies and granules. The outer segments are scarce end little differentiated. The basal processes of pinealocytes do not contain any synaptical ribbons, and the basal light cells (sensory nerve cells of Kappers, do not show any synaptical contact with pinealocytes. Secretion was demonstrated at the apices as well as at the basal processes of the pinealocytes. Thus, although the architecture of pineal organs resembles that of other photosensorial epithelia, there is little evidence that the pinealocytes of lizards are involved in photosensory activity. There are intra-epithelial nerve processes, apparently having synaptical contact with cell processes of unknown origin. They seem to be efferent nerves. The parietal nerve passing the pineal organ outside its rostral wall sometimes seems to be divided into 2 branches. In 1 case the thicker one, located at the left, consisted of 275 fibers, 34 of which are myelinated. In serial sections both parietal nerves have been traced to the parietal eye. There is evidence that they cross below the tip of the pineal organ.