 Dear students, in this topic we shall discuss the concepts of osmoregulation and excretion. You know that water is a solvent in cells which makes solutions with solutes that is salts, electrolytes and ions which are dissolved in water. Each cell is adapted to a defined quantity of water in relation to salts to perform its functions normally. Changes in the concentration of either water or the solutes in it disturb the osmotic balance. Osmoregulation and excretion are those homeostatic mechanisms which maintain water and solute balance in the cell and in the body of an animal. Osmoregulation is the mechanism of regulation of solutes and concentration of water in the cells and body fluids of animals. While excretion is the mechanism which eliminates nitrogenous wastes from the body. These metabolic nitrogenous wastes, for example ammonia and eurya disturb the osmotic balance in animal cells at toxic levels because they disturb the osmotic balance and therefore their body's removal, because of their toxicity, their body's removal, that is excretion in the high is necessary to maintain osmotic balance because they disturb the osmotic balance and their body's removal, that is why excretion and osmoregulation are correlated processes. Students, now we shall discuss the concepts of osmolarity. Cells consistently encounter changing extracellular environment. An external medium which is dilute as compared to cells' concentration of solutes. While a more concentrated external environment is termed as hypertonic, an environment which resembles in solute concentration to that of present inside the cell is termed as isotonic. These hypotonic or isotonic solutions, they are called osmolarities of the solutions. The osmolarity has solution key, it has wide effects on the performance of animal cells. Hypotonic environments osmotically cause the entry of water into the cell. These results in dilution of the cell contents and cause it to become turgid or swell or even burst. Hypotonic environments its opposite effects produce and they cause the cell to lose water and to cause the cell solution to become more concentrated. Here students, now we shall discuss the importance of osmoregulation. Animal cells require a critical balance of water and solutes in the body. They cannot survive in net gain or loss of water. Water continuously enters and leaves the body. However, the quantity of water and solutes is kept in balance because of osmoregulation.