Question

Which of these will be the immediate effect if gaseous exchange in the lung capillaries reduce? A. Blood will flow in the reverse direction. B. Pulmonary veins will receive blood with less oxygen. C. The space inside the left and right atrium will increase. D. The pressure of blood inside the capillaries will decrease.​

Answer 1

Answer will be option B.

Explanation:

• In lungs gaseous exchanges take place between Alveolar air and blood within pulmonary capillaries.
• Deoxygenated blood enter pulmonary capillaries through pulmonary arteries which has pO2 of 40 mm hg and pCo2 of 46 mm hg.
• Alveolar air has a pO2 of 100 mm hg and pCo2 of 40mm hg
• so oxygen diffuse from alveoli into the blood through the respiratory membrane down their concentration gradient and carbon di oxide diffuse out of the blood into alveoli down their concentration gradient
• Pulmonary vein then collect this oxygenated blood from pulmonary capillaries.
• If gaseous exchange is reduced then less oxygen will diffuse into the blood and less carbon di oxide will diffuse out of the blood. So, the blood collected by pulmonary vein will have less oxygen than usual and contain carbon di oxide more than usual.
• so option B. will be correct i.e. pulmonary vein will receive blood with less oxygen