Question

In human beings, partial pressure of carbon dioxide in the inspired and expired air is respectively.
A) 0.3 and 40mm Hg
B) 0.3 and 32mm Hg
C) 40 and 46mm Hg
D) 40 and 0.3mm Hg

Answer 1

Hint:- The aim of the respiratory system is to exchange gases. It is important to understand the fundamental concepts of gases and their behaviour in order to understand the processes of gas exchange in the lungs. Several other gas laws help to define the actions of gases, in addition to Boyle 's law.

Complete Answer:-
For this gas exchange method, pulmonary ventilation supplies air to the alveoli. Gases pass across the membranes at the respiratory membrane, where the alveolar and capillary walls cross, with oxygen joining the bloodstream and leaving carbon dioxide. Blood is oxygenated by this process and carbon dioxide, the waste product of cellular respiration, is eliminated from the body.
Ventilation and perfusion are two essential components of gas exchange in the lungs. Ventilation is the passage of oxygen into and out of the lungs, and in the pulmonary capillaries, perfusion is the flow of blood. The volumes involved in ventilation and perfusion should be consistent in order for gas exchange to be successful. However, breathing and perfusion may be imbalanced by causes such as regional gravity influences on blood, blocked alveolar ducts, or illness.
External respiration occurs as a result of oxygen and carbon dioxide partial pressure changes in the pulmonary capillaries between the alveoli and the blood. Oxygen diffuses from the alveolus to the capillary through the respiratory membrane in external respiration, while carbon dioxide diffuses through the alveolus from the capillary. While the solubility of oxygen in the blood is not high, the partial pressure of oxygen in the alveoli varies significantly from that of the pulmonary capillaries in the blood.
The discrepancy is about 64 mm Hg: the partial oxygen pressure in the alveoli is approximately 104 mm Hg, while the partial oxygen pressure in the capillary blood is approximately 40 mm Hg. The partial pressure of carbon dioxide in the capillary blood is about 45 mm Hg, while the partial pressure of carbon dioxide in the capillary blood is about 40 mm Hg. However, in all blood and alveolar fluids, the solubility of carbon dioxide is much greater than that of oxygen by a ratio of about 20. As a consequence, the relative oxygen and carbon dioxide concentrations that disperse across the respiratory membrane are identical.
From these discussions we can conclude that 40 and 46mm Hg is the required partial pressure of carbon dioxide in the inspired and expired air respectively in human beings.
Therefore the correct answer is option (C).

Note:- Ventilation is the mechanism that brings oxygen into and out of the alveoli, and the flow of blood in the capillaries is affected by perfusion. In gas exchange, both are essential, as ventilation must be adequate to produce a high partial oxygen pressure in the alveoli. If breathing is inadequate and the partial oxygen pressure in the alveolar air decreases, the capillary is constrained and the blood supply is diverted to properly ventilated alveoli.