Question

The concentration of dissolved $C{O}_2$ in blood varies in different blood vessels. Choose the most appropriate option with decreasing order of dissolved $C{O}_2$ concentration in the blood vessels.

• A. Pulmonary artery $>$ Skin capillaries $>$ Aorta $>$ Alveolar capillaries
• B. Alveolar capillaries $>$ Aorta $>$ Skin capillaries $>$ Pulmonary artery
• C. Pulmonary artery $>$ Aorta $>$ Alveolar capillaries $>$ Skin capillaries
• D. Skin capillaries $>$ Pulmonary artery $>$ Aorta $>$ Alveolar capillaries

Answer 1

The correct option is A Pulmonary artery $>$ Skin capillaries $>$ Aorta $>$ Alveolar capillaries

The concentration of dissolved CO₂ in blood is directly proportional to its partial pressure i.e., more the partial pressure more is the concentration and solubility in blood.

Partial pressure of CO₂ in different blood vessels is as follows:

pCO₂ in pulmonary artery = 46 mm Hg

pCO₂ in aorta = 45 mm Hg

pCO₂ in alveolar capillaries = 40 mm Hg

Since skin capillaries contain arterial blood, pCO₂ is almost same as that of aorta but due to respiration of cells, CO₂ concentration is increased and so pCO₂ is a little bit higher in them. Hence, the decreasing order of CO₂ concentration in different blood vessels will be :

Pulmonary artery >> Skin capillaries >> Aorta >> Alveolar capillaries

So, the correct answer is A.