You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is During standing. In apex of lung - and explain in detail?
Ans. is "c" i.e., V/Q is high o Due to gravity, the apical alveoli are both underventilated and underperfused while the basal alveoli are both overventilated and overperfused.o However, gravity affects perfusion much more than it affects ventilation.o Hence, apical alveoli are more underperfused than underventilated while the basal alveoli are more overperfused than overventilated.o Therefore, V/Q is maximun at apex (about 3.0) and least at base (about 0.6).o Since ventilation is far in excess of perfusion at apex, comparatively little oxygen is transferred from the alveoli to the blood, and CO2 transferred to the alveoli is also less.o Hence the gas tension at the apices are quiet close to those of inspired air, i.e., High PaO2 and low PaCO2.o On the other hand, at the base of lung perfusion is better than ventilation; Hence PaO2 and PaCO2 of basal alveoli are quiet close to those of pulmonary artery, i. e., low PaO, and high PaCO2o In simple words, ventilation-perfusion mismatch is responsible for high PO2 with low PCO2 at apex and Low PO2 with high PCO2 at base.