Which of the following changes occur in diaphragm and intercostal mus...
Changes in diaphragm and intercostal muscles during expiration:
During expiration, the process of expelling air from the lungs, several changes occur in the diaphragm and intercostal muscles. The correct answer is option 'c', which states that the external intercostal muscles and diaphragm relax. Let's understand why this is the correct answer.
1. Function of the diaphragm:
The diaphragm is a dome-shaped muscle located at the base of the thoracic cavity. It plays a crucial role in respiration by separating the thoracic and abdominal cavities. During normal breathing, the diaphragm contracts and moves downward, increasing the volume of the thoracic cavity.
2. Function of the external intercostal muscles:
The external intercostal muscles are located between the ribs. They play a significant role in increasing the size of the thoracic cavity during inhalation. These muscles contract during inspiration, lifting the ribcage upward and outward, thereby expanding the thoracic cavity and allowing air to enter the lungs.
3. Expiration process:
Expiration is the process of expelling air from the lungs. During expiration, the diaphragm and external intercostal muscles undergo relaxation.
4. Relaxation of the diaphragm:
When the diaphragm relaxes, it moves back to its dome-shaped position. This relaxation decreases the volume of the thoracic cavity, causing an increase in the pressure within the lungs. This increased pressure forces the air out of the lungs.
5. Relaxation of the external intercostal muscles:
The external intercostal muscles also relax during expiration. This relaxation allows the ribcage to move downward and inward, reducing the size of the thoracic cavity. As a result, the pressure within the lungs increases, facilitating the expulsion of air.
Therefore, during expiration, the external intercostal muscles and diaphragm both relax. This relaxation of the muscles aids in reducing the volume of the thoracic cavity, increasing the pressure within the lungs, and expelling air from the respiratory system.
Which of the following changes occur in diaphragm and intercostal mus...
Expiration is a process by which foul air (carbon dioxide) is expelled out from the lungs. Expiration is a passive process that occurs as follows.
The muscle fibres of the diaphragm relax making it convex, decreasing the volume of the thoracic cavity. Internal intercostal muscles contract so that they pull the ribs downward and inward decreasing the size of the thoracic cavity. Contraction of the abdominal muscles such as external and internal oblique muscles compresses the abdomen and pushes its contents (viscera) towards the diaphragm, thus further decreasing the volume of the thoracic cavity. This results in an increase in the pressure inside the thoracic cavity as compared to the atmospheric pressure which results in the expiration of air.
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