Gas Exchange in Lungs
Gas exchange in the lungs is the process by which oxygen from inhaled air passes into the blood, while carbon dioxide from the blood is expelled into the air to be exhaled. This occurs in tiny air sacs called alveoli, where oxygen diffuses through thin walls into surrounding capillaries, and carbon dioxide moves from the blood into the alveoli. This exchange is essential for respiration and maintaining healthy body function.
Gas Exchange in Lungs
Gas exchange in the lungs is the process by which oxygen from inhaled air passes into the blood, while carbon dioxide from the blood is expelled into the air to be exhaled. This occurs in tiny air sacs called alveoli, where oxygen diffuses through thin walls into surrounding capillaries, and carbon dioxide moves from the blood into the alveoli. This exchange is essential for respiration and maintaining healthy body function.
💡 Key Takeaways
- Explain how oxygen moves from the alveoli into the blood and carbon dioxide moves from the blood into the alveoli by diffusion driven by partial pressure differences.
- Identify the structures involved in gas exchange—alveoli and pulmonary capillaries—and the thin respiratory membrane, plus the role of surfactant in maintaining efficient diffusion.
- Describe how diffusion is influenced by surface area, membrane thickness, and ventilation–perfusion (V/Q) matching.
- Explain how oxygen is transported in blood by hemoglobin and how carbon dioxide is carried (as bicarbonate and dissolved CO₂), linking transport to gas exchange.
❓ Frequently Asked Questions
Where does gas exchange occur in the lungs?
Gas exchange happens in the alveoli, across the thin alveolar–capillary membrane where O2 diffuses into blood and CO2 diffuses into the alveolar air.
How does oxygen move from air into the bloodstream?
Oxygen diffuses down its partial pressure gradient from alveolar air (about 100 mmHg) into the blood (about 40 mmHg) and binds to hemoglobin in red blood cells.
How is carbon dioxide removed from the blood?
CO2 diffuses from blood (higher PCO2) into the alveolar air (lower PCO2) to be exhaled; it is carried in blood as bicarbonate and other forms before diffusing into the alveoli.
What factors influence how efficiently gas exchange occurs?
Factors include alveolar surface area, thickness of the alveolar–capillary membrane, ventilation–perfusion (V/Q) matching, and conditions that alter these (e.g., emphysema, fibrosis).