Human Anatomy - Kotsan I. Y. 2009

Endocrine glands
Paraganglia - chromaffin organs

Paraganglia are isolated clusters of chromaffin Cells that originate from the primordium of the sympathetic Nervous system and are closely associated with sympathetic ganglia. Due to their property of staining with chromium salts, they are referred to as chromaffin Organs. The endocrine function of these structures is analogous to that of The adrenal medulla.

In humans, during various periods of prenatal and Postnatal development, as well as in adulthood, chromaffin tissue is dispersed throughout different PARTS OF THE body, yet it is always associated with the Autonomic nervous system. Small individual clusters of chromaffin tissue can be found along the digestive tract and within sympathetic ganglia. These clusters undergo regression relatively early in life. They are most prominent in early childhood and are typically undetectable in adults. The most constant and persistent ones are the carotid body and the lumbar-aortic paraganglia.

The carotid body (glomus caroticum) is located on the posterior and medial surfaces of the common carotid artery near its bifurcation into the external and internal carotid Arteries. In shape, it resembles a grain of rice. In children, its dimensions do not exceed 1–2 mm, while in adults they range from 8 × 2 mm to 3 × 2 mm.

The lumbar-аortic paraganglia are located as small, thin strips on both sides of the aorta at the level of Water/144.html">Origin of the inferior mesenteric artery. They are present in newborns and infants. In newborns, their dimensions are 8–15 × 2–3 mm. After the first year of life, they begin to regress and disappear by the age of 2–3 years. The typical chromaffin cells that comprise them eventually degenerate into Connective Tissue with age.

Paraganglia are also found along the subclavian and renal arteries. Occasionally, an inconstant supercardiac paraganglion is present, located between the pulmonary trunk and the aorta.