During inspiration muscles of diaphragm

Options

A. Contracts
B. Expands
C. No effect
D. Coiled like string

Answer

**Step-by-Step Solution:**

1. **Understanding Inspiration**: During inspiration, the body takes in air. This process involves specific movements of the diaphragm and intercostal muscles.

2. **Role of the Diaphragm**: The diaphragm is a dome-shaped muscle located at the base of the thoracic cavity. When we inhale, the diaphragm contracts and moves downward.

3. **Effect of Diaphragm Contraction**: As the diaphragm contracts, it increases the volume of the thoracic cavity. This increase in volume leads to a decrease in the pressure inside the lungs (intrapulmonary pressure).

4. **Pressure Changes**: According to Boyle's Law, when the volume of a container increases, the pressure inside that container decreases. Therefore, as the volume of the thoracic cavity increases due to diaphragm contraction, the intrapulmonary pressure decreases.

5. **Airflow into the Lungs**: The decrease in intrapulmonary pressure creates a pressure difference between the atmosphere (higher pressure) and the inside of the lungs (lower pressure). This pressure gradient causes air to flow into the lungs from the atmosphere.

6. **Conclusion**: Therefore, during inspiration, the diaphragm contracts, leading to an increase in thoracic volume and a decrease in intrapulmonary pressure, which allows air to enter the lungs.

**Final Answer**: During inspiration, the muscles of the diaphragm **contract**.

---