| Alveoli | Nephrons |
| Shape. They are rounded or polyhedral. | They are elongated tubules, |
| Components. Alveoli are single entities. | Each nephron has two components-Malpighian capsule and renal tubule. Renal tubule has three parts – PCT, loop of Henle and DCT. |
| Blood Capillaries. They are of one type and lie all over the alveoli. | Blood capillaries form two patches-glomerulus and peritubular capillaries |
| Materials. They deal with respiratory gases. | They deal with body fluids. |
| Function. Alveoli perform exchange of gases between blood and inhaled air. | Nephrons bring about separation of waste products from blood. |