| No. | Alveoli | Nephrons |
| 1. | Alveoli are pouch-like air sacs that are made up of simple squamous epithelium. | 1. Nephrons are the elongated tubules that form an anatomical and functional unit of the kidney. |
| 2. | It has a thin cell wall to facilitate gaseous exchange. | 2. Each nephron has Bowman's capsule, proximal convoluted tubule, a loop of the nephron, distal convoluted tubule and the collecting ducts. |
| 3. | It is surrounded by blood capillaries. | 3. Blood capillaries are present as glomerulus and peritubular capillaries. |
| 4. | Presence of millions of alveoli in lungs provide ample surface area to facilitate gaseous exchange between air in alveoli and blood in capillaries. Oxygen diffuses across the alveolar and capillary wall into the bloodstream while carbon dioxide diffuses from blood across the mentioned walls into the alveoli. | 4. It serves in fluid and electrolyte balance of the body through the process of urine formation. Each part performs different role in urine formation. |