Fill up the blanks in the following paragraph by selecting the correct option.
The movement of air into and out of the lungs is carried out by creating a (i).____ between the lungs and the atmosphere. Inspiration can occur if intra-pulmonary pressure is (ii).____ Expiration takes place when the intra-pulmonary pressure is (iii).____ than the atmospheric pressure. Expiration takes place when the intra-inspiration is initiated by the (iv).____ of diaphragm which (v).____the volume of thoracic chamber in the antero-posterior axis.

Options

A. `{:("(i)",(ii),(iii),(iv),(v)),("concentration gradient","less","higher","relaxation","increases"):}`
B. `{:("(i)",(ii),(iii),(iv),(v)),("concentration gradient","higher","less","contraction","decrease"):}`
C. `{:("(i)",(ii),(iii),(iv),(v)),("pressure gradient","higher","less","relaxation","decrease"):}`
D. `{:("(i)",(ii),(iii),(iv),(v)),("pressure gradient","less","higher","contraction","increase"):}`

Answer

### Step-by-Step Solution:

1. **Understanding the Mechanism of Breathing**:
- Breathing consists of two main phases: inspiration (inhaling) and expiration (exhaling).
- The movement of air into and out of the lungs is facilitated by pressure differences between the lungs and the atmosphere.

2. **Filling in the Blanks**:
- (i) The movement of air into and out of the lungs is carried out by creating a **pressure gradient** between the lungs and the atmosphere.
- (ii) Inspiration can occur if intra-pulmonary pressure is **less** than the atmospheric pressure.
- (iii) Expiration takes place when the intra-pulmonary pressure is **greater** than the atmospheric pressure.
- (iv) Expiration takes place when the inspiration is initiated by the **contraction** of the diaphragm.
- (v) The contraction of the diaphragm **increases** the volume of the thoracic chamber in the antero-posterior axis.

3. **Final Paragraph**:
- The movement of air into and out of the lungs is carried out by creating a **pressure gradient** between the lungs and the atmosphere. Inspiration can occur if intra-pulmonary pressure is **less**. Expiration takes place when the intra-pulmonary pressure is **greater** than the atmospheric pressure. Expiration takes place when the inspiration is initiated by the **contraction** of the diaphragm which **increases** the volume of the thoracic chamber in the antero-posterior axis.