Structure- Alveoli are tiny balloon like structures present inside the lungs. Its walls are made of an extensive network of blood capillaries. Nephrons are tubular structure present inside the kidney. It is made of renal capsule and renal tubule. Thin walled capillaries are found inside the nephrons.

Functioning- Alveoli are the sites of gaseous exchange; oxygen and carbon dioxide are exchanged between the blood of capillaries and the gases present in the alveoli. Nephrons regulate the concentration of water and salts by filtering the blood, reabsorbing what is needed and excreting the non-required as urine