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If the mouth and nose are closed at the peak of a complete inspiration, but before expiration, and the breath is held, what is the pressure of gases within the alveoli relative to the pressure of atmospheric air?
- a)Alveolar pressure is greater than the pressure of atmospheric air
- b)Alveolar pressure is equal to the pressure of atmospheric air
- c)Alveolar pressure is less than the pressure of atmospheric air
- d)Cannot be predicted without more information
Correct answer is option 'A'. Can you explain this answer?
Verified Answer
If the mouth and nose are closed at the peak of a complete inspiration...
When the breath is held after a complete inspiration, the closure of the mouth and nose prevents the escape of air from the lungs. As a result, the volume of air in the lungs remains constant, but the metabolic activity of the body continues, leading to the production of carbon dioxide (CO2) as a waste product.
As CO2 accumulates in the alveoli, it diffuses into the pulmonary capillaries and enters the bloodstream. This results in an increase in the partial pressure of CO2 in the alveoli. The increased partial pressure of CO2 in the alveoli leads to a higher total pressure of gases within the alveoli, including both oxygen (O2) and CO2. This higher total pressure is greater than the pressure of atmospheric air.
Therefore, the pressure of gases within the alveoli, including O2 and CO2, is greater than the pressure of atmospheric air when the breath is held after a complete inspiration with the mouth and nose closed.
Most Upvoted Answer
If the mouth and nose are closed at the peak of a complete inspiration...
Explanation:
When the mouth and nose are closed at the peak of a complete inspiration and the breath is held, the pressure of gases within the alveoli is greater than the pressure of atmospheric air.
Alveoli and Pressure:
- The alveoli are tiny air sacs in the lungs where gas exchange occurs. Oxygen from the inhaled air diffuses from the alveoli into the bloodstream, while carbon dioxide, a waste product, diffuses from the bloodstream into the alveoli to be exhaled.
- The pressure within the alveoli is determined by the balance between the forces that promote inspiration (inhalation) and expiration (exhalation).
Inspiration and Expiration:
- During inspiration, the diaphragm and other respiratory muscles contract, causing the volume of the thoracic cavity to increase. This expansion lowers the pressure within the lungs, creating a pressure gradient that allows air to flow in.
- During expiration, the diaphragm and respiratory muscles relax, and the volume of the thoracic cavity decreases. This increased pressure within the lungs pushes air out.
Hold Breath at Peak Inspiration:
- When the mouth and nose are closed at the peak of a complete inspiration and the breath is held, the muscles involved in expiration are relaxed. The thoracic cavity remains expanded, and the volume of the lungs is increased.
- However, since there is no airflow, the pressure within the alveoli remains higher than the pressure in the atmosphere.
- This is because the pressure within the alveoli is determined by the elastic recoil of the lungs and chest wall, which tends to collapse the lungs. The alveolar pressure is therefore higher than atmospheric pressure to keep the airways open and prevent lung collapse.
Conclusion:
Therefore, at the peak of a complete inspiration when the breath is held, the pressure of gases within the alveoli is greater than the pressure of atmospheric air. This pressure difference allows for the maintenance of lung inflation and helps to keep the airways open.
When the mouth and nose are closed at the peak of a complete inspiration and the breath is held, the pressure of gases within the alveoli is greater than the pressure of atmospheric air.
Alveoli and Pressure:
- The alveoli are tiny air sacs in the lungs where gas exchange occurs. Oxygen from the inhaled air diffuses from the alveoli into the bloodstream, while carbon dioxide, a waste product, diffuses from the bloodstream into the alveoli to be exhaled.
- The pressure within the alveoli is determined by the balance between the forces that promote inspiration (inhalation) and expiration (exhalation).
Inspiration and Expiration:
- During inspiration, the diaphragm and other respiratory muscles contract, causing the volume of the thoracic cavity to increase. This expansion lowers the pressure within the lungs, creating a pressure gradient that allows air to flow in.
- During expiration, the diaphragm and respiratory muscles relax, and the volume of the thoracic cavity decreases. This increased pressure within the lungs pushes air out.
Hold Breath at Peak Inspiration:
- When the mouth and nose are closed at the peak of a complete inspiration and the breath is held, the muscles involved in expiration are relaxed. The thoracic cavity remains expanded, and the volume of the lungs is increased.
- However, since there is no airflow, the pressure within the alveoli remains higher than the pressure in the atmosphere.
- This is because the pressure within the alveoli is determined by the elastic recoil of the lungs and chest wall, which tends to collapse the lungs. The alveolar pressure is therefore higher than atmospheric pressure to keep the airways open and prevent lung collapse.
Conclusion:
Therefore, at the peak of a complete inspiration when the breath is held, the pressure of gases within the alveoli is greater than the pressure of atmospheric air. This pressure difference allows for the maintenance of lung inflation and helps to keep the airways open.
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If the mouth and nose are closed at the peak of a complete inspiration, but before expiration, and the breath is held, what is the pressure of gases within the alveoli relative to the pressure of atmospheric air?a)Alveolar pressure is greater than the pressure of atmospheric airb)Alveolar pressure is equal to the pressure of atmospheric airc)Alveolar pressure is less than the pressure of atmospheric aird)Cannot be predicted without more informationCorrect answer is option 'A'. Can you explain this answer? for MCAT 2025 is part of MCAT preparation. The Question and answers have been prepared according to the MCAT exam syllabus. Information about If the mouth and nose are closed at the peak of a complete inspiration, but before expiration, and the breath is held, what is the pressure of gases within the alveoli relative to the pressure of atmospheric air?a)Alveolar pressure is greater than the pressure of atmospheric airb)Alveolar pressure is equal to the pressure of atmospheric airc)Alveolar pressure is less than the pressure of atmospheric aird)Cannot be predicted without more informationCorrect answer is option 'A'. Can you explain this answer? covers all topics & solutions for MCAT 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for If the mouth and nose are closed at the peak of a complete inspiration, but before expiration, and the breath is held, what is the pressure of gases within the alveoli relative to the pressure of atmospheric air?a)Alveolar pressure is greater than the pressure of atmospheric airb)Alveolar pressure is equal to the pressure of atmospheric airc)Alveolar pressure is less than the pressure of atmospheric aird)Cannot be predicted without more informationCorrect answer is option 'A'. Can you explain this answer?.
If the mouth and nose are closed at the peak of a complete inspiration, but before expiration, and the breath is held, what is the pressure of gases within the alveoli relative to the pressure of atmospheric air?a)Alveolar pressure is greater than the pressure of atmospheric airb)Alveolar pressure is equal to the pressure of atmospheric airc)Alveolar pressure is less than the pressure of atmospheric aird)Cannot be predicted without more informationCorrect answer is option 'A'. Can you explain this answer? for MCAT 2025 is part of MCAT preparation. The Question and answers have been prepared according to the MCAT exam syllabus. Information about If the mouth and nose are closed at the peak of a complete inspiration, but before expiration, and the breath is held, what is the pressure of gases within the alveoli relative to the pressure of atmospheric air?a)Alveolar pressure is greater than the pressure of atmospheric airb)Alveolar pressure is equal to the pressure of atmospheric airc)Alveolar pressure is less than the pressure of atmospheric aird)Cannot be predicted without more informationCorrect answer is option 'A'. Can you explain this answer? covers all topics & solutions for MCAT 2025 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for If the mouth and nose are closed at the peak of a complete inspiration, but before expiration, and the breath is held, what is the pressure of gases within the alveoli relative to the pressure of atmospheric air?a)Alveolar pressure is greater than the pressure of atmospheric airb)Alveolar pressure is equal to the pressure of atmospheric airc)Alveolar pressure is less than the pressure of atmospheric aird)Cannot be predicted without more informationCorrect answer is option 'A'. Can you explain this answer?.
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