Carotid body containsislands of two types of cells, type I and type II cells, surrounded by fenestrated sinusoidal capillaries. Type I cells are excited byhypoxia, and the principal transmitter appears to be

Carotid & Aortic Bodies There is a carotid body near the carotid bifurcation on each side, and there are usually two or more aortic bodies near the arch of the aorta . Each carotid and aortic body (glomus) contains islands of two types of cells, type I and type II cells, surrounded by fenestrated sinusoidal capillaries. Type I cells The type I or glomus cells are closely associated with cup-like endings of the afferent nerves. The glomus cells resemble adrenal chromaffin cells and have dense-core granules containing catecholamines that are released upon exposure to hypoxia and cyanide . The cells are excited byhypoxia, and the principal transmitter appears to be dopamine, which excites the nerve endings by way of D2 receptors. Type II cells The type II cells are glia-like, and each surrounds four to six type I cells. Their function is probably sustentacular.