The ultrastructure of the secretory cells of the human carotid body.

Objective: The purpose of this study was to study the ultrastructure of the human carotid body by using transmission electron microscopy. This is to distinguish the secretory cells of the human carotid body and classify the cells by the characteristic size, shape and electron density of the secretory granules, since nowadays there is still no data about TEM of the human carotid body. There is also no report about the exact secretions of the organ. Methods: 4 carotid bodies at the carotid bifurcations were identified and dissected from 2 fresh cadavers. The specimens were prepared for routinely TEM. Results: There are at least 3 secretory cell types in the human carotid body accordings to TEM. The cells were classified by the characteristic size, shape and the electron density of the secretory granules. The type I has large clear membrane bound granules, type II has small electron dense membrane bound granules and type III has large moderately electron dense membrane bound granules while type IV is thought to be the degranulated form of the type I. Conclusion: There are at least 3 types of secretory cell in the human carotid body and there may be 3 types of secretion as well. The immunocytochemical technique will be performed in future to identify the secretions.