THE INTRINSIC INNERVATION OF THE PULMONARY VESSELS

Abstract

The intrinsic innervation of the pulmonary vessels has been studied using a variety of methods. The extrapulmonary parts of the arteries and veins are richly innervated in all the species studied. On entering the lungs the veins retain a substantial innervation in the cat, guinea pig and rat, but in the monkey the nerves become relatively sparse. Conversely the intrapulmonary parts of the arteries of the monkey have a profuse innervation, while the arteries of the other animals mentioned are poorly innervated. The possibility that these species differences are chemical rather than morphological is discussed. Nerve cells are associated with the extrapulmonary vessels and occasionally with the vessels inside the lungs. These latter are scanty and must be relatively unimportant. Two or more types of nerve cells can be identified, and the possibility that primary sensory neurons are admixed with effector neurons cannot be excluded. Structures resembling complex endformations occur in the extrapulmonary parts of the arteries and veins. Some or all of these may be artefacts, because they increase in number and become more distinct if the vessels are deliberately subjected to trauma such as stretching or deep-freezing during the process of preparation.