Vascular Histology (III): Pressure sensors (Baroreceptors) .

Aortic bodies or baroreceptors. Baroreceptors are found in the atrial-venous junctions and are easily identified in the adventitia of the aortic wall near the root and the ascending portion of the vessel. These baroreceptors are though to be the end organs of small nerve endings and function as pressure sensors. On cursory microscopic examination, they can be confused with small periaortic lymph nodes. ­­Other parasympathetic ganglia are present throughout the adventitia of the aorta, and in some regions they form discrete structures such as the carotid bodies or the organ of Zuckerdandl. A. Light micrograph of a fetal aorta with its adventitial layer and the edge of an aortic body (right lower corner) (H&E 20 X). B. Higher magnification view of the aortic body shown in A. The cells are eosinophilic and pale. These bodies are well vascularized, like their counterpart in the carotid bifurcation and along the thoracic and abdominal aorta (50 X). C. In adults, these bodies are larger in size but much smaller in relative proportion. The cells are round, pale and form glomus-like structures with a dense network of vessels and collagen. Small bundles of baroreceptor cells branch to and from these bodies (H&E 150X). D. The collagen network of the aortic bodies is shown (Masson trichrome 150X). E. These bodies do not have prominent elastic lamellae, although elastic fibers have been shown by ultrastructural studies (Verhoeff 150X). F. The pale cells contain few glycogen granules (PAS 150X).

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