Question

In normal expiration the diaphragm is-
A) Arched
B) Flattened
C) Not involved
D) Perforated

Answer 1

Hint: Expiration is a breathing exercise where air is expelled out from the lungs into the external environment. During this process, the diaphragm relaxes and also there is a decrease in the thoracic cavity.

Complete answer:
Lungs are present in the thoracic cavity. There is a muscle sheet called diaphragm which allows the other parts of the respiratory system like trachea, bronchi to conduct air to the lungs.
During inhalation the diaphragm contracts causing expansion of the thoracic cavity. This gives a flattened appearance because of the enlarged diaphragm.
Then, during expiration or exhalation the contracted diaphragm relaxes to reduce the volume of the thoracic cavity giving itself an arched appearance.

Let us analyze the options to find out the correct option.
Option A: In normal expiration the diaphragm is arched. Therefore, this is the correct option.
Option B: Flattened appearance of diaphragm is during inspiration. Therefore, this is an incorrect option.
Option C: Diaphragm is involved in the process of breathing. Therefore, this is an incorrect option.
Option D: Perforated diaphragm is a result of tear or injury in the diaphragm. Therefore, this is an incorrect option.

Hence the correct answer is option (A) i.e, Arched.

Note:
-Expiration is a passive process which starts by relaxation of the inspiratory muscles.
-This relaxation causes the thoracic cavity’s volume to decrease making them return to their original size.
-This increases the pressure within lungs according to Boyle's law.
-Since the pressure is more inside than the external environment, hence air is expelled out.