How does the body keep itself working properly?
Millions of chemical reactions take place in the body, and because they can influence one another, they all need to be kept in balance. This process is called homeostasis, and it ensures that the whole complicated system works smoothly, and that problems are usually overcome before they can cause illness. The brain monitors what happens within the body and controls everything by means of nerves and chemical messengers called hormones that switch chemical reactions on and off as needed.
What is excretion?
Excretion is the removal of waste material from the body. Most of this material is removed from the blood by the kidneys, but waste carbon dioxide produced by the activity of the cells is removed by the lungs, and other waste is excreted as sweat, through the skin. The liver gets rid of many poisonous materials by making them harmless and passing them on to the kidneys.
What is urine?
Urine is the liquid produced in the kidneys and discharged from the bladder when we pass water. It contains waste materials.
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