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Due to which forces the air from outside...

Due to which forces the air from outside move into the lungs
(i) An increase in pulmonary volume
(ii) Decrease the intra-pulmonary pressure
(iii) Reduction in thoracic volume

A

i and ii

B

i, ii, iii

C

i and iii

D

ii, iii

Text Solution

AI Generated Solution

The correct Answer is:
To understand the forces that cause air to move from outside into the lungs, we need to analyze the three options provided: 1. **Increase in Pulmonary Volume**: - When the diaphragm contracts and the rib cage expands, the volume of the thoracic cavity increases. This increase in volume leads to a decrease in pressure within the lungs (intrapulmonary pressure). According to Boyle's Law, when the volume of a container increases, the pressure inside that container decreases. Therefore, as the pulmonary volume increases, air is drawn into the lungs from the outside due to the pressure difference. 2. **Decrease in Intrapulmonary Pressure**: - As the volume of the lungs increases during inhalation, the intrapulmonary pressure drops below atmospheric pressure. This pressure difference creates a vacuum effect, causing air to flow into the lungs. The intrapulmonary pressure typically becomes lower than the atmospheric pressure (approximately -4 mmHg), which facilitates the movement of air into the lungs. 3. **Reduction in Thoracic Volume**: - A reduction in thoracic volume occurs during expiration, not during inhalation. When the thoracic cavity decreases in volume, the pressure inside the lungs increases, pushing air out of the lungs rather than drawing it in. Therefore, this option does not contribute to the movement of air into the lungs. **Conclusion**: The correct forces that cause air to move into the lungs are (i) an increase in pulmonary volume and (ii) a decrease in intrapulmonary pressure. Thus, the correct answer is options (i) and (ii).
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