Question

Select the correct events that occur during inspiration?

(a) Contraction of diaphragm

(b) Contraction of external intercostal muscles

(c) Pulmonary volume decrease

(d) Intra pulmonary pressure increase

• A. (a), (b) and (d)
• B. Only (d)
• C. Both (a) and (b)
• D. Both (c) and (d)

Answer 1

The correct option is C

Both (a) and (b)

The correct option is C.

Explanation of the correct option:

Option C:

1. Diaphragm is a large muscular dome-shaped structure that helps during respiration.
2. Diaphragm contracts during inspiration creating more volume for the lungs to expand and take in more air.
3. The small muscles present between each rib bone, starting from the first rib and extending down to the 11th rib are known as external intercostal muscles.
4. These muscles contract to elevate the ribs during inspiration. This process then helps to expand the lungs and facilitate the entry of air into them.

Explanation of the incorrect options:

Option A:

1. The intrapulmonary pressure also known as intrapleural pressure does not increase but decreases during the inspiration process.
2. The average intrapulmonary pressure of a human lung is 759 mmHg or lower.
3. The lower intrapulmonary pressure than the atmospheric pressure allows the air to be sucked in creating an equilibrium.
4. Hence, this is an incorrect option.

Option B:

This is an incorrect option as the intrapulmonary pressure increases during the process of inspiration.

Option D:

1. Pulmonary volume is known as the respiratory volume which is the total volume of gas inside the lungs.
2. It increases during the respiratory process.
3. The pulmonary volume of an average human lung is 6 liters and hence, this is an incorrect option.

Final answer: During inspiration contraction of the diaphragm and contraction of external intercostal muscles occurs.