Question

When diaphragm of man is completely dome shaped it shows
A. End of expiration and beginning of inspiration
B. Beginning of expiration and end of inspiration
C. Increased rate of breathing
D. Decreased rate of breathing

Answer 1

Hint: A diaphragm is a dome shaped muscular structure separating thorax from abdomen in mammals. Its main function is it helps in breathing by increasing or decreasing the chest volume.

Complete Answer:
The diaphragm is a c-shaped muscular fibrous tissue. Diaphragm is located below the lungs and separates the thoracic cavity from abdomen which domes upward. It is a thin muscular sheet like structure which plays a major role in respiration. It contracts and relaxes rhythmically and involuntarily.

Mechanism of breathing:
- It is the main muscle involved in breathing. It helps in increasing and decreasing the lungs volume.
- During inhalation: The diaphragm contracts and moves downward. It enlarges the volume of the chest cavity which creates a partial vacuum in the thorax. This forces the lung to expand and draws air from outside.
- During Expiration: The diaphragm relaxes and attains its original dome shape and the air is exhaled by the recoil of the lungs and other tissues. This process is supported by both intercostal muscles and abdominal muscles.

Thus the correct answer is (B). Diaphragm of man is completely dome shaped; it shows the beginning of expiration and end of inspiration.

Note: Apart from breathing, the diaphragm is also involved in non respiratory functions like expel vomit, faeces and urine. It also aids in childbirth. It also plays a significant role in strength training.