Urine
 | This article does not have any sources. (January 2021) |
Urine (also called pee) is a liquid that is created by the body, in the kidneys. It is stored in the bladder and comes out of the human body through the urethra, a tube which leads from the bladder to the urethral meatus (meatus is an opening in the body), at the tip of the penis (men) or the vulva (women). Urination is how the body gets rid of unwanted or unneeded substances in the blood. Urine is the liquid that these substances are put in. Some slang terms for urine are "pee", "wee", "wee wees" and "piss".
After the blood has circulated through the body, its composition has changed. This is because some substances in the blood have been absorbed by the body and because the body has released other substances into the blood. The blood has also absorbed substances produced from food and drink. The liver removes many toxins (harmful substances) and adds other substances that the blood needs (like amino acids, proteins, coagulation factors, hormones, for example). Then the kidneys remove excess amounts of salts (like urea) by putting them into the urine. After the blood has passed through the liver and the kidneys, it has the correct composition that the body needs.
Urine is mostly water, and contains mineral salts, and about 2% urea, which is produced in the liver to remove ammonia. Ammonia is a very toxic substance and has to be removed. It is made by breaking down food and some medications and drugs. Urea has very low toxicity, although a continuously high level of urea in the blood (a condition called hyperuricemia) can cause disease.
The color of urine normally ranges from colourless to yellow. The yellow color is caused by urobilins. These are produced by the breakdown of hemoglobin, the substance that gives blood its red color. If a person is dehydrated, less urine will be produced (maybe less than one liter per day),[source?] and it will be more concentrated. If a person drinks a lot of water, though, more urine will be produced (maybe as much as two liters per day) and it will be less concentrated.
Urine lets the body get rid of:
- Extra water
- Extra electrolytes (salts)
- Urea (mostly not needed by the body)
- Drugs
- Toxins (poisons in the body)( Note that most toxins are removed in the bile of the liver, which transfers the toxins to the feces. Many descriptions of urine say that some toxins are removed in urine, but do not say what toxins these are).
