Alveoli
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Respiratory
- Respiratory Overview
- Airway Anatomy
- Alveoli
- Breathing Mechanics
- Gas Exchange in Tissues
- Nervous Control of Breathing
- Respiratory Defense Systems
- Alveoli
- Function: gas exchange
- Site of oxygen and carbon dioxide exchange between air and bloodstream
- Alveoli have high pO2 and low pCO2
- Gases diffuse down their concentration gradients
- High concentration → low concentration
- O2 diffuses from lungs to pulmonary capillaries
- CO2 diffuses from pulmonary capillaries to lungs
- Hyperventilation
- Equilibrium shifts towards CO2 (less CO2), less bicarbonate ions
- Hypoventilation
- Equilibrium shifts towards bicarbonate ions (more CO2)
- Gases diffuse down their concentration gradients
- Structure
- Alveoli are tiny sacs of elastic lung tissue, surrounded by capillaries
- Alveoli
- Walls are one cell thick to allow for rapid gas exchange
- Large surface area to volume ratio to maximize diffusion for small amount of gas
- Surfactant coats alveolar surface to reduce surface tension
- Prevent alveoli from collapsing
- Composed of amphipathic phospholipids
- Capillaries
- Extremely narrow that RBCs must pass through single file = maximizes surface area for gas exchange
- Large total surface area to maximize gas exchange
- Function: gas exchange