Due to the effects of gravity, the lungs receive uneven regional blood flow from the apex to the base of the lung when we stand i an upright position. The transmural pressure (pressure above atmospheric) in the right ventricle is 2.3 x10 Pa (or 23 emH>0). The lung height (H) 1s 30 cm, and the pulmonary artery enters the lung half-way up. There 1s a pressure drop of 1x10 Pa in the arteries between the pulmonary artery and the capillaries. blood = | gram/cm a) b) c) d) 3 gravity = 980 em/sec?, 1 = 0.03 gram/(cm *sec) Pulmonary Capillaries Pulmonary Zone 1 Arteries . > Zone 2 Right Ventricle Zone 3 QD Zone 4 Q___ > Show that the hydrostatic gradient of pressure in the vertical direction in the pulmonary arteries is about 0.1x10 Pa per centimeter vertical distance. Use the result of part (a) plus the given data to calculate the pressure at the entrance to the capillaries at the verv top. the very bottom, and half-way up the lung (that 1s, at the level of the right ventricle). Assume the pulmonary capillary radius (r) 1s Spm and that their length (L) 1s 100pm. Exit L Entrance l r 0 ) Pulmonary Capillary The average velocity of blood flow (vVmean) 1 the pulmonary capillaries 1s 0.2 em/sec. . : . . r2 d Use the Poiseuille flow expression for mean flow velocity Uppqn = (2) to Su dx calculate the pressure drop across the capillary. Assuming the actual pressure drop (since the flow in the capillaries 1s NOT a Poiseuille flow) 1s 5 times what you calculated in part (c), calculate the pressure that exists at the exit of the capillaries at the very top. very bottom, and half-way up the lung. Calculate the location of the highest point in the lung where the capillaries are fully open along their entire length