Oxygen and carbon dioxide diffuse across thin alveolar and capillary walls down concentration gradients.
Alveolar walls are one cell thick, moist, surrounded by capillaries. Steep gradients are maintained by ventilation and blood flow. Surfactant reduces surface tension.
Partial pressure gradients drive diffusion. Haemoglobin loads oxygen quickly. Carbon dioxide is transported mostly as bicarbonate.
Example: pulmonary oedema thickens the barrier and reduces exchange.
Oxygen and carbon dioxide diffuse across thin alveolar and capillary walls down concentration gradients.
Gas Exchange in Alveoli is one of the 51 topics in Human Physiology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Blood Vessels, Respiratory System, Lung Compliance and Surfactant.
Emphysema destroys alveolar walls, reducing area.
Work through the Beginner topics in Human Physiology first, such as Homeostasis, Tissues and Organs, Skeletal System, then return to Gas Exchange in Alveoli. Intermediate topics assume the Beginner vocabulary.
The closest topics to Gas Exchange in Alveoli are Blood Vessels, Respiratory System, Lung Compliance and Surfactant, Altitude Physiology. Comparing them side by side is a good way to see how the ideas connect.
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Gas Exchange in Alveoli. To practise the whole of Human Physiology, use the Human Physiology quiz.
Gas Exchange in Alveoli: Oxygen and carbon dioxide diffuse across thin alveolar and capillary walls down concentration gradients. Blood Vessels: Arteries carry blood away from the heart, veins return it and capillaries exchange materials. Read both side by side and note what each one explains.
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Blood Vessels and explain the difference aloud. Finally, take the Human Physiology quiz and come back to this page for any question you miss.
Arteries carry blood away from the heart, veins return it and capillaries exchange materials.
❤️ Human PhysiologyAirways and lungs that bring oxygen in and remove carbon dioxide.
❤️ Human PhysiologySurfactant reduces alveolar surface tension, preventing collapse and easing breathing.
❤️ Human PhysiologyLow oxygen triggers erythropoietin, raising red cell count over days and weeks.
❤️ Human Physiology