BIOM20002 Lecture Notes - Lecture 54: Partial Pressure, Extracellular Fluid, Arteriole
Document Summary
Amount of fluid in here is controlled by starlings forces. So need low hydrostatic pressure there to maintain thin layer of interstitial fluid. If you have high hydrostatic pressure you get pulmonary edema. Blood pressure of pulmonary circulation is low for alveolar perfusion - 25/8mmhg. 10% of blood volume (0. 5 litres) at any given time. Net hydrostatic pressure filtering fluid out of capillary low. Lung interstitial fluid volume usually minimal reduces distance between alveolar air space & capillary. Distensibility & large total cross-sectional area of pulmonary arterioles. Local control mechanisms attempt to match ventilation and perfusion. Not all alveoli are getting the same ventilation at any one time (e. g. blockages, posture squeezes some shut) Blood will reroute to alveoli that are highly ventilated. Less ventilation = less perfusion to that alveoli + an attempt to increase ventilation. If ventilation decreases in alveoli, pco2 increases and po2 decreases.
