Alveoli Nephron 1. Alveoli are functional unit of lungs. 1. Nephrons are functional unit of kidney. 2. A mature lung has about 30 crore alveoli. 2. A kidney has about 10 lakh nephrons. 3. Alveoli provide a wide surface for gaseous exchange. 3. The surface area of a nephron is not much more. 4. The exchange of O2 and CO2 takes place through the network of capillaries in alveoli. 4. The Bowman’s capsule in nephron regulates the concentration of water and salts.