Question

Use the words inspiration and expiration to describe the part of the breathing cycle that occurs as a result of each of the following:

a. The diaphragm contracts.

b. The volume of the lungs decreases.

c. The pressure within the lungs is less than that of the atmosphere.

Short answer

a. During the process of contraction of the diaphragm the volume of thoracic cavity increases which is known as inspiration.

b. When the volume of lungs decreases the pressure inside the lungs increases so air will flow out which is known as expiration.

c. When the pressure in lungs is less than that of atmosphere air will flow inside the lungs which is known as inspiration.

Step-by-step solution

Part(a) Step 1: Given information

We need to find the process taking place in contraction of diaphragm.

Part(a) Step 2: Explanation

When the diaphragm contracts and the rib cage expands, the thoracic cavity expands, causing the volume of the thoracic cavity to grow. When the thoracic cavity expands, the lungs' flexibility permits them to expand. According to Boyle's law, as the capacity of the lungs rises, the pressure inside the lungs drops, eventually falling below the atmospheric pressure. A pressure gradient exists between the lungs and the atmosphere due to this difference in pressures. Molecules flow from a higher pressure location to a lower pressure area in a pressure gradient. Air rushes into the lungs during the inhalation phase of breathing, known as inspiration, until the pressure within the lungs equals the pressure in the environment.

Part(b) Step 1: Given information

We need to find the process takes place when the volume of lungs decreases.

Part(b) Step 2: Explanation

The thoracic cavity's volume shrinks, which squeezes the lungs and reduces their volume. Expiration occurs when the pressure in the lungs exceeds the pressure in the environment, causing air to flow out of the lungs.

Part(c) Step 1: Given information

We need to find the process which takes place when pressure in lungs is less than that of atmosphere.

Part(c) Step 2: Explanation

According to Boyle's law, as the capacity of the lungs rises, the pressure inside the lungs drops, eventually falling below the atmospheric pressure. A pressure gradient exists between the lungs and the atmosphere due to this difference in pressures. Molecules flow from a higher pressure location to a lower pressure area in a pressure gradient. Air rushes into the lungs during the inhalation phase of breathing, known as inspiration, until the pressure within the lungs equals the pressure in the environment.