Secretory Granule Types

Abstract

The various exocrine and endocrine glands as well as single exocrine, endocrine and neuroendocrine cells scattered in different organs, and some neurons store their excretory products in secretory granules. In addition, a wide range of cells including the different types of leukocytes, macrophages, mast cells, platelets, T lymphocytes, melanocytes, type II alveolar epithelial cells, and endothelial cells contain secretory granules. All types of secretory granules are sealed off by a membrane. But their size and shape, and the appearance of their content differ greatly by electron microscopy. The latter largely depends on the chemical nature of the stored products (which can be identified by immunoelectron microscopy) and a few examples are presented here.