Osmoregulation is the active regulation of the osmotic pressure of an organisms body fluids to maintain the homeostasis of the organisms water content. It is the process of maintaining salt and water balance across membranes within the body. Osmotic pressure is a measure of the tendency of water to move into one solution from another by osmosis. The higher the osmotic pressure of a solution, the more water tends to move into it. The key features of osmoregulation are:
-
Fluid balance: Osmoregulation maintains the fluid balance and the concentration of electrolytes (salts in solution which in this case is represented by body fluid) to keep the body fluids from becoming too diluted or concentrated.
-
Osmoconformers and osmoregulators: There are two major types of osmoregulation. Osmoconformers are organisms that try to match the osmolarity of their body with their surroundings. In other words, these organisms maintain the same osmotic pressure inside the body as outside water. They conform either through active or passive means. Most marine invertebrates such as starfish, jellyfish, and lobsters are osmoconformers. Osmoregulators, on the other hand, actively regulate their internal osmolarity, regardless of the external environment. Humans and most other warm-blooded organisms are osmoregulators.
-
Osmoreceptors: Osmoreceptors are specialized cells that can detect changes in osmotic pressure. Humans and most other warm-blooded organisms have osmoreceptors in the hypothalamus. Besides the brain, osmoregulators are also found in the kidneys.
-
Kidneys: The kidneys serve as the main osmoregulatory organs in the human body. They filter the blood and remove excess water and electrolytes, which are then excreted as urine.
Osmoregulation is critical to sustaining many bodily functions, including metabolic and biochemical reactions, transport of nutrients, and thermoregulation.
