Studies on intra-arterial cushions. III. The cushions at the origin of the rat carotid body artery (CBA).

The orifice of the rat carotid body artery is surrounded by intra-cranial cushions which form a boat-like structure. The cushions are covered by normally looking endothelium, ramified smooth muscle cells are seen in its stroma. The internal elastic lamella remifies where the cushions originate, and delicate elastic fibres extend into the cushions. Axon profiles are confined to the medioadventitial border. They were never seen to penetrate into the tunica media or even to reach the cushions. It is suggested that the cushions are passively flattened during pulsatile dilatation of the external carotid artery.