The Carotid Body as Part of a Unified Sympathoadrenal System of Neural Crest Derivatives: Insights from Two Centuries of Research.

The carotid body-a chemoreceptive derivative of the neural crest located at the bifurcation of the carotid artery-has been studied for over 282 years. The history of research into this small but vital organ is full of unexpected turns and offers many valuable lessons. Initially considered part of a unified system of paraganglia performing the endocrine function, the carotid body was later reclassified and recognized as a chemosensory organ. This article highlights the key controversies encountered by past researchers. These contradictions though largely forgotten, remain unresolved. The aim of our article is to propose a unified model of the carotid body that integrates its endocrine and chemosensory structural aspects. As we show, the main problem in studying the carotid body was its isolated investigation, detached from other organs of the sympathoadrenal system. Only a comprehensive analysis of the carotid body with other components of this system has allowed researchers to form a more complete understanding of both the structure and function of these formations. Contrary to the prevailing view of the carotid body as the main peripheral chemoreceptor organ, it may also perform endocrine functions during certain periods of human ontogeny. It is these potential functions that may explain the presence of certain morphological structures in the carotid body, the significance of which has until recently remained a mystery.