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In mammals and birds, low oxygen levels in the lungs cause a constriction of the pulmonary vasculature that increases the
 

Summary: In mammals and birds, low oxygen levels in the lungs cause
a constriction of the pulmonary vasculature that increases the
resistance to pulmonary blood flow and elevates the pulmonary
arterial blood pressure (Euler and Liljestrand, 1946; Faraci et
al. 1984). This response is locally mediated and can be
demonstrated in denervated lungs that are devoid of external
neurohumoral influences (e.g. Fishman, 1976). Hypoxic
pulmonary vasoconstriction (HPV) is believed to be important
for the local matching of perfusion and ventilation by diverting
pulmonary blood flow from poorly ventilated to well-
ventilated regions of the lung (Euler and Liljestrand, 1946;
Marshall et al. 1994c; Brimioulle et al. 1996). The effects of
hypoxia on pulmonary vascular resistance have not been
studied in reptiles, and it is not known whether the structurally
simple lungs of these animals display HPV. In non-crocodilian
reptiles, the ventricle is not fully divided and, with the notable
exception of varanid lizards (e.g. Burggren and Johansen,
1982; Heisler et al. 1983), the distribution of blood flows
between the pulmonary and systemic circulations is largely
determined by differences in vascular resistances (cf. Hicks

  

Source: Altimiras, Jordi - Department of Biology, Linköpings Universitet

 

Collections: Environmental Sciences and Ecology