Q. 8.24 - An Introduction to General, Organic, and Biological Chemistry

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 relaxes, moving up into the thoracic cavity.

b. The volume of the lungs expands.

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

Step-by-Step Solution

Answer

a. The diaphragm relaxes, moving up into the thoracic cavity results in contraction of thoracic cavity which is known as expiration.

b. The volume of the lungs expands causes air to flow inside the lungs which is known as inspiration.

c. The pressure within the lungs is higher than that of the atmosphere causes air to flow out of the lungs known as expiration.

Part(a) Step 1: Given information

We need to identify the process when the diaphragm relaxes, moving up into the thoracic cavity. 

Part(a) Step 2: Explanation

Expiration, or the exhalation phase of breathing, happens when the diaphragm relaxes and returns to its resting position in the thoracic cavity. The thoracic cavity's volume shrinks, which squeezes the lungs and reduces their volume. Because the pressure in the lungs is now higher than the pressure in the environment, air is forced out by expiration.

Part(b) Step 1: Given information

We need to identify the process when volume of lungs expands.

Part(b) Step 2: Explanation

According to Boyle's law, as the volume of the lungs increases, the pressure inside the lungs drops, eventually falling below the atmospheric pressure. The lungs and the atmosphere are separated by a pressure gradient caused by the difference in pressures. Molecules flow from a higher pressure location to a lower pressure area in a pressure gradient. Inspiration occurs when air rushes into the lungs during the inhalation phase of breathing.

Part(c) Step 1: Given information

We need to identify the process the pressure within the lungs is higher than that of the atmosphere.

Part(c) Step 2: Explanation

Expiration, or the exhalation phase of breathing, happens when the diaphragm relaxes and returns to its resting position in the thoracic cavity. The thoracic cavity's volume shrinks, which squeezes the lungs and reduces their volume. Because the pressure in the lungs is now higher than the pressure in the environment, air is forced out by expiration.