00:00 / 00:00
Airflow, pressure, and resistance
Alveolar gas equation
Breathing cycle and regulation
Diffusion-limited and perfusion-limited gas exchange
Fick's laws of diffusion
Gas exchange in the lungs, blood and tissues
Ideal (general) gas law
Reading a chest X-ray
Respiratory system anatomy and physiology
Alveolar surface tension and surfactant
Combined pressure-volume curves for the lung and chest wall
Compliance of lungs and chest wall
Carbon dioxide transport in blood
Oxygen binding capacity and oxygen content
Oxygen-hemoglobin dissociation curve
Anatomic and physiologic dead space
Lung volumes and capacities
Pulmonary changes at high altitude and altitude sickness
Pulmonary changes during exercise
Pulmonary chemoreceptors and mechanoreceptors
Regulation of pulmonary blood flow
Ventilation-perfusion ratios and V/Q mismatch
Zones of pulmonary blood flow
The primary role of the lungs is to ensure gas exchange between the external environment, and the blood within the circulatory system.
This happens thanks to a series of branching tubes called airways, which conduct the air down into small thin-walled sacs called alveoli, which are wrapped in an intricate network of tiny blood vessels called pulmonary capillaries.
And the alveolo-capillary membrane, where the layer of alveolar cells lining the alveoli meets the endothelial cells that make up the pulmonary capillary, is where gas exchange occurs.
Now, before we delve into diffusion, perfusion and their limits, remember that gas exchange across the alveolo-capillary membrane happens according to Fick’s law.
Fick’s law states that the net rate of diffusion - V of any particular gas across the alveolar-capillary membrane, is proportional to the pressure gradient across the wall; which is the difference between the partial pressure of the gas in the alveolar sacs, or PA, and the partial pressure of the gas in the blood, or Pa, and also proportional to the surface area of the wall, or A, but inversely proportional to the wall’s thickness - T. And this is all times the diffusion constant - D, which varies from gas to gas.
So, diffusion-limited gas exchange means that a gas like oxygen or carbon dioxide can diffuse across the alveolo-capillary membrane as long as the partial pressure gradient is maintained.
Latest on COVID-19
Nurse Practitioner (NP)
Physician Assistant (PA)
Create custom content
Raise the Line Podcast
Copyright © 2024 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Cookies are used by this site.
Terms and Conditions
USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.