The structural organization of the pineal complex in the domestic goose

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Abstract
The light and electron microscopic structure of the pineal complex of the domestic goose was studied. The complex is tubulofollicular but there is no direct connection between the constituent system of ducts and the third ventricle of the brain. Within the pineal, blood vessels accompanied by sympathetic nerve bundles are confined to the connective tissue. Other nerve fibers and occasional nerve cell bodies, however, do occur among the pineal cells. Three basic pineal cell types were distinguished: (1) elongate epithelial cells which are arranged around follicles and ducts and resemble degenerate photo‐receptor cells; (2) intramural supportive cells which are interspersed with elongate epithelial and intramural supportive cells; and (3) small supportive cells which lie between the bases of the elongate epithelial and intramural supportive cells. The follicular structure, vascularization, presence of secretory granules, and the nature of the elongate epithelial cells indicate that the pineal complex is primarily endocrine though a possible photoreceptive function cannot be ignored. Vesicles, 100‐300 and 40‐100 nm wide, were found within nerves and intramural supportive cells. The larger vesicles, present in pineals collected in the night, probably contain peptidic hormones. The smaller vesicles present in both day and night samples probably contain aminergic hormones.