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A Sphincter in the Pulmonary Artery of the Frog Rana temporaria and Its Influence on Blood Flow in Skin and Lungs
Author(s) -
SaintAubain M. L.,
Wingstrand K. G.
Publication year - 1979
Publication title -
acta zoologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.414
H-Index - 37
eISSN - 1463-6395
pISSN - 0001-7272
DOI - 10.1111/j.1463-6395.1979.tb00609.x
Subject(s) - anatomy , rana , pulmonary artery , sphincter , biology , left pulmonary artery , reflex , respiration , medicine , neuroscience
Abstract A sphincter is described in the a. pulmonalis in the frog Rana temporaria. The sphincter begins abruptly where the pulmonary artery branches off from the a. pulmo‐cutanea. It is constricted by vagal stimulation and acetylcholine. It also contracts actively when the lungs are artificially collapsed and opens when the lungs are inflated. It is suggested that previously reported fibers in the vagus nerve, which come from stretch receptors in the lungs, act as the afferent reflex arch. When the pulmonary artery constricts, the cutaneous artery and vein are distended by increased pressure which contributes to increased cutaneous flow. The sphincter therefore seems to play an important role in the adjustment of circulation to exclusive cutaneous respiration as for instance in submerged, wintering frogs. It is suggested that the decrease of pulmonary flow in such situations causes increased mixing in the heart and, perhaps, complete break‐down of the double circulation. In frogs with exclusive skin respiration this would seem to be a functional necessity. Sphincters of similar location in turtles seem to be homologous with the one in Rana.