Question

Which of the following associations between the two stages of respiration and the contraction of muscles is correct? A. Inhalation-diaphragm relaxes B. Inhalation-intercostal muscles relax C. Exhalation-diaphragm contracts D. Exhalation-intercostal muscles relax

Short answer

D. Exhalation-intercostal muscles relax

Step-by-step solution

- Understanding Inhalation

Inhalation is the process of taking air into the lungs. During this phase, the diaphragm contracts and moves downward and the intercostal muscles (the muscles between the ribs) also contract, causing the rib cage to expand.

- Understanding Exhalation

Exhalation is the process of expelling air from the lungs. During this phase, the diaphragm relaxes and moves upward into a dome shape, and the intercostal muscles relax, causing the rib cage to return to its original position.

- Analyzing the Choices

Evaluate each given association based on the understanding of inhalation and exhalation: A. Inhalation-diaphragm relaxes (Incorrect, as diaphragm contracts during inhalation). B. Inhalation-intercostal muscles relax (Incorrect, as intercostal muscles contract during inhalation). C. Exhalation-diaphragm contracts (Incorrect, as diaphragm relaxes during exhalation). D. Exhalation-intercostal muscles relax (Correct, as intercostal muscles relax during exhalation).

Key concepts

Inhalation

Inhalation is the process of drawing air into the lungs. This phase is active and requires the diaphragm and intercostal muscles to work together.
When you breathe in, the diaphragm, which is the main muscle responsible for breathing, contracts and moves downward. This creates more space in the chest cavity and reduces the pressure inside the lungs compared to the outside atmosphere.
To further assist in expanding the chest cavity, the intercostal muscles between the ribs also contract. This action lifts the rib cage up and outward, allowing more air to flow into the lungs.

• The diaphragm contracts and flattens.
• The intercostal muscles contract and lift the rib cage.

These movements result in decreased lung pressure, drawing air in through the nose and mouth, and filling the lungs with oxygen.

Exhalation

Exhalation is the process of expelling air from the lungs. Unlike inhalation, exhalation is generally a passive process.
During exhalation, the diaphragm relaxes and moves back to its dome-shaped position. This occurs because the muscle no longer needs to contract.
Similarly, the intercostal muscles also relax, causing the rib cage to move back down and inward. This restoration to its original state reduces the space in the chest cavity and increases the pressure in the lungs, pushing air out.

• The diaphragm relaxes and rises.
• The intercostal muscles relax and lower the rib cage.

The increase in lung pressure forces air, now rich in carbon dioxide, out of the lungs through the airways and out through the nose or mouth.

Diaphragm

The diaphragm is a large, dome-shaped muscle located at the base of the lungs. It plays a crucial role in the respiratory process.
When the diaphragm contracts, it flattens and moves downward. This contractions create more space in the chest cavity, making it easier for air to enter the lungs.
Conversely, when the diaphragm relaxes, it returns to its dome shape, and this movement helps push air out of the lungs.

• The diaphragm contracts to facilitate inhalation.
• The diaphragm relaxes to aid exhalation.

This muscle is essential for breathing and works in conjunction with other muscles to ensure efficient movement of air.

Intercostal Muscles

Intercostal muscles are muscles located between the ribs. They also play a significant role in the breathing process.
During inhalation, the external intercostal muscles contract, causing the rib cage to lift and expand. This action creates more space in the chest cavity, allowing the lungs to fill with air.
In contrast, during exhalation, the intercostal muscles relax. This relaxation causes the rib cage to drop back to its resting position, which helps expel air from the lungs.

• External intercostal muscles contract during inhalation.
• Intercostal muscles relax during exhalation.

The coordinated movements of these muscles are essential for the respiration process and ensure that inhalation and exhalation occur smoothly.