Urinary System

Excretion can be defined as the removal of toxic waste products of metabolism from the body. These wastes can be either solid, liquid or in the gaseous state. The liquid wastes are ammonia and urea, which exist in the blood along with the nutrients and other useful substances. So there is a need of complex organ that may separate or filter out the dissolved excretory wastes from blood while retaining the nutrients in the latter. Two kidneys in human beings are the organs that perform this task. There is a distinct advantage of the two kidneys in our body. If one kidney fails, the other can still deal with functions of excretion and regulation.

The kidneys are solid, bean-shaped, reddish brown-paired structures, which lie in the abdominal cavity one on either side of the vertebral column. The kidneys collect the excretory products and eliminate them in the form of urine, which then passes down the two tubular ureters into the collapsible urinary bladder, which is a muscular reservoir of urine. The urine is released periodically to the outside via the urethra.

Interesting Urine Facts:

- Adults pass about a quart and a half of urine each day, depending on the fluids and foods consumed.

- The volume of urine formed at night is about half of that formed in the daytime.

- Normal urine is sterile. It contains fluids, salts and waste products, but it is free of bacteria, viruses and fungi.

- The tissues of the bladder are isolated from urine and toxic substances by a coating that discourages bacteria from attaching and growing on the bladder wall.

- The human bladder can stretch to hold about 400 ml of urine.

- All the blood in our body passes 400 times through each kidney every day.

- Urine therapy uses urine by applying it to the skin or drinking it; this is common practice in traditional medicine in India.

- Since urine contains large amounts of urea, it is an excellent source of nitrogen for plants and a good accelerator for compost; it is thousands of times less toxic than ammonia. Gardeners often recommend a dilution of 10-15 parts water to one of urine for application to pot plants and flower beds during the growing season.

- The ancient Romans used urine as a bleaching agent for cleaning clothes.

- People adrift at sea or lost in the desert for long periods often resort to drinking their urine when no rainwater is available. However, this won't prevent you from dying of dehydration, especially if it causes vomiting.

- Urine has historically been used as an antiseptic. In times of war, when other antiseptics were unavailable, urine, the darker the better, was utilized on open wounds to kill bacteria.

- The yellow colour of urine was once thought to come from gold. Alchemists in the middle ages spent much time trying to extract gold from urine. Of course, they were unsuccessful, but along the way made other discoveries, including white phosphorus and urea.