What is the primary function of the external intercostal muscles during respiration?
Solution
Correct Answer: Option B
- The primary function of the external intercostal muscles is to facilitate inhalation during the respiratory process.
- These muscles are located between the ribs, with fibers running obliquely downward and forward from the rib above to the rib below.
- During inhalation, the external intercostal muscles contract, which causes the ribs to be elevated and moved outward.
- This action increases the volume of the thoracic cavity, leading to a decrease in intrathoracic pressure. As a result, air is drawn into the lungs.
- In contrast, the muscles primarily responsible for forced expiration are the internal intercostal muscles and abdominal muscles, which help push air out of the lungs by decreasing thoracic volume. The external intercostals do not compress the abdominal contents nor are they involved in stabilizing the thoracic cage during breath-holding.
Key points:
- External intercostal muscles contract during inhalation
- Elevate and expand the rib cage
- Volume of thoracic cavity increases
- Air is drawn into the lungs (inspiration)
Reference: Gray's Anatomy, 42nd Edition, Respiratory System, Chapter 7
- These muscles are located between the ribs, with fibers running obliquely downward and forward from the rib above to the rib below.
- During inhalation, the external intercostal muscles contract, which causes the ribs to be elevated and moved outward.
- This action increases the volume of the thoracic cavity, leading to a decrease in intrathoracic pressure. As a result, air is drawn into the lungs.
- In contrast, the muscles primarily responsible for forced expiration are the internal intercostal muscles and abdominal muscles, which help push air out of the lungs by decreasing thoracic volume. The external intercostals do not compress the abdominal contents nor are they involved in stabilizing the thoracic cage during breath-holding.
Key points:
- External intercostal muscles contract during inhalation
- Elevate and expand the rib cage
- Volume of thoracic cavity increases
- Air is drawn into the lungs (inspiration)
Reference: Gray's Anatomy, 42nd Edition, Respiratory System, Chapter 7
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