Distribution of pulmonary stretch receptors in the intrapulmonary airways of the dog

Abstract

Fifty-eight pulmonary stretch receptors from 41 dogs have been localized in the intrapulmonary airways of the left lung through a direct dissection into the lung parenchyma. The intrapulmonary stretch receptors account for 44.4% of the total and their distribution in the intrapulmonary airways was 7.6% in the lobar bronchi, 18.4% in bronchi having a diameter greater than 1 mm and 18.4% in the remaining airways. Of all the receptors 82.8% were at an average distance of 3.1±0.2 cm (S.E.) from the lung root, thus within a volume approximately equal to 1 25 of the end-expiratory volume of the lung. The concentration of stretch receptors along the intrapulmonary airways was calculated from the surface area of the bronchial tree at different levels on the assumption of 2000 receptors from one lung. These data, together with those referring to extrapulmonary airways, show that the concentration nearly doubles going from the upper intrathoracic trachea to the lobar bronchi (from 34.8 receptors/cm 2 to 60.5/cm 2) and then sharply decreases to 7.0/cm 2 in bronchi having a diameter greater than 1 mm and 0.2/cm 2 in the smaller intrapulmonary airways.