The presence of paraganglia in the human ascending aortic fold: histological and ultrastructural studies.

Light and electron microscopic features of the human ascending aortic fold are described. Histological examination showed the characteristic epicardial structures continuous with a stroma of abundant adipose tissue. In addition, randomly distributed tissue resembling the carotid body was observed by both light and electron microscopy throughout postnatal life, from a fullterm stillborn fetus to the oldest subject (65 y). The size of the paraganglionic cell nests was variable at all ages. The presence of paraganglia in the aortic fold raises the possibility that they are concerned with chemoreception.