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Pressure in the Lungs and Pleural Cavity quiz #1

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  • What is the role of intrapleural pressure in keeping the lungs inflated, and how does it compare to intrapulmonary pressure?
    Intrapleural pressure is the negative pressure within the pleural cavity that acts like suction, resisting the lungs' natural tendency to collapse due to elasticity and surface tension. It is always less than intrapulmonary pressure, and as long as intrapulmonary pressure is greater than intrapleural pressure, the lungs remain inflated.
  • How does surfactant affect the surface tension within the alveoli, and why is this important for lung function?
    Surfactant reduces the surface tension within the alveoli, making it easier for the lungs to expand and preventing alveolar collapse. This is important because high surface tension would otherwise cause the alveoli to stick together and collapse, making breathing difficult.
  • What are the three key pressures involved in lung ventilation, and what are their typical values relative to atmospheric pressure?
    The three key pressures are atmospheric pressure (760 mmHg at sea level), intrapulmonary pressure (equalizes with atmospheric pressure, fluctuating about ±2 mmHg), and intrapleural pressure (always negative, typically -4 to -6 mmHg relative to atmospheric pressure).
  • Why do the lungs have a natural tendency to collapse, and what prevents this from happening under normal conditions?
    The lungs tend to collapse due to their elastic recoil and the surface tension of fluid in the alveoli. This is prevented by the negative intrapleural pressure, which creates a suction effect that keeps the lungs expanded.
  • What two main forces contribute to the lungs' natural tendency to collapse?
    The lungs tend to collapse due to their elastic recoil (from elastin and collagen) and the surface tension of fluid in the alveoli.
  • How does surfactant help prevent alveolar collapse in the lungs?
    Surfactant reduces the surface tension within the alveoli, making it easier for the lungs to expand and preventing the alveoli from sticking together and collapsing.
  • What is intrapleural pressure and how does it keep the lungs inflated?
    Intrapleural pressure is the negative pressure within the pleural cavity that acts like suction, resisting the lungs' tendency to collapse and keeping them inflated.
  • How does intrapleural pressure compare to intrapulmonary pressure under normal conditions?
    Intrapleural pressure is always less than intrapulmonary pressure, and as long as this relationship is maintained, the lungs remain inflated.
  • What are the three key pressures involved in lung ventilation and their typical values relative to atmospheric pressure?
    The three key pressures are atmospheric pressure (760 mmHg at sea level), intrapulmonary pressure (equalizes with atmospheric pressure, fluctuating about ±2 mmHg), and intrapleural pressure (always negative, typically -4 to -6 mmHg relative to atmospheric pressure).
  • Why is it dangerous if intrapleural pressure equals intrapulmonary pressure?
    If intrapleural pressure equals intrapulmonary pressure, the suction effect is lost, allowing the lungs to collapse because the inward forces are no longer resisted.
  • Is thoracentesis performed to inflate a collapsed lung, and what is its actual purpose in relation to pleural cavity pressure?
    Thoracentesis is not performed to inflate a collapsed lung. Its actual purpose is to remove excess fluid or air from the pleural cavity, which can help restore the negative intrapleural pressure necessary to keep the lungs inflated. By removing fluid or air, thoracentesis can relieve pressure on the lung and allow it to re-expand if it has collapsed due to loss of negative pressure.