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Osmoregulation is one of the major process by which animals maintain homeostasis of fluids. "Osmoregulation is the active regulation of osmotic pressure of body fluids to keep them from becoming too dilute or too concentrated" (Solomon Animals in all environments (aquatic and terrestrial) must maintain the right concentration of solutes and amount of water in their body fluids; this involves excretion: getting rid of metabolic wastes and other substances such as hormones which would be toxic if allowed to accumulate in the blood via organs such as the skin and the kidneys; keeping the water and dissolved solutes in balanced is referred to as osmoregulation.

Table of contents
1 Forms of osmoregulation
2 Vertebrate excretory systems
3 References

Forms of osmoregulation

Two major types of osmoregulation are osmoconformers and osmoregulators. Osmoconformers are animals that allow their body fluid concentration to vary with the environment. An example are marine fish. By drinking in sea water, and actively excreting salt out from the gills, the fish will gain salt as it produces an isotonic urine. Omoregulators are more common in the animal kingdom. Osmoregulators actively control salt concentrations despite the salt concentrations in the environment. An example are freshwater fish. The gills actively uptake salt from the environment. Water will diffuse into the fish where the fish will excrete a very hypotonic urine to expel all the excess water.

Kidneys play a very large role in human osmoregulation. Kidneys regulate the amount of water in urine waste. With the help of naturally producing hormones such as antidiuretic hormone, aldosterone, and angiotensin II, the human body can increase permeability of the collecting ducts in the kidney to reabsorb water and prevent it from being excreted.

A major way animals have evolved to osmoregulate is by controlling the amount of water excreted through the excretory system.

Vertebrate excretory systems

Waste products of nitrogen metabolism

Ammonia is a toxic by-product of protein metabolism and is generally converted to less toxic substances after it is produced then excreted; mammals convert ammonia to urea while birds and reptiles form uric acid to be excreted with other wastes via their cloacas.

How osmoregulation is achieved in vertebrates

Four processes occur: