Urinary system

Urinary system of the body plays a crucial role in our sustenance. Also referred to as the genitourinary or excretory system of the body, this system is responsible for the elimination of various metabolic waste materials from the body, in the form of urine. Essential nutrients from food ingested, is absorbed and used for their respective uses in the body. The remaining waste in the bowel and blood needs to be thrown out, thus, the kidney in coordination with the lungs, intestines and skin evacuates all wastes in the body. If the elimination of these waste substances is not done, accumulation of the same can conduce to poisoning. The urinary system gets rid of urea and other waste materials from the blood and produces urine to throw them out. Moreover, this system also controls the amount of water and mineral salts to be absorbed back into the bloodstream.

Parts of the Urinary System

The urinary system comprises two kidneys, two ureters, one bladder and urethra. All these parts of the urinary system coordinate with each other and eliminate wastes. Let us have a closer look at these parts and their functioning to understand the working of the urinary system.

 Kidneys: We have two bean-shaped, purplish-brown organs placed just below the rib cage, near the mid portion of the back. Approximately the size of one's fist, the kidneys are made up of myriads of infinitesimal filters, called nephrons, which are the functional units of the kidneys. Blood containing metabolic wastes are passed through these nephrons, which filter the urea from the blood. The remaining 99% of the body fluid is sent back to the body minus the urea. The urea filtered out is combined with water and other waste materials like organic materials and excess salts to form urine. So kidneys are sites of urine production! About one to two liters of urine is produced on a daily basis, depending on the amount of water consumed each day. Besides this, kidneys are also responsible for maintaining fluid and salt balance in the body, thereby maintaining blood consistency. 


Ureters: Two tube-like structures called ureters connect the kidneys to the urinary bladder. The ureters are pipelines through which the waste-rich urine passes from the kidney to the bladder. Ureters feature the presence of muscles in their walls which undergo continuous contraction and relaxation movements, so as to force the urine downward towards the bladder. Every 10-15 seconds urine trickles from the kidneys and collects in the bladder. 

 Urinary Bladder: This pear-shaped, hollow organ is situated in the pelvic region and is kept in place by ligaments that bind it to the pelvic bones. Like ureter muscles, these muscles also contract and relax constantly. The muscles relax to allow entry of urine from ureter and contract (when full) to send urine out of the body, via the urethra. On an average, the bladder can hold about two cups of urine, however, the urge to urinate will begin when the bladder is about a cup full. The circular sphincter muscles present around the bladder's opening prevents the urine from leaking out from the bladder. The bladder does not release urine until it is full. Thank goodness the bladder waits till it's full! 

Urethra: When the bladder is gorged with urine, the nerves in the bladder send signals to one's brain to urinate. The brain in response sends signals to bladder muscles to contract and release the stored urine. The sphincter muscles also receive instructions from the brain to allow the urine to pass out. Urine exits from the bladder through a small tube called urethra, out of the body. 

Interesting Urinary System Facts for Kids

•  In a healthy adult, almost 440 gallons of blood is passed through the kidneys on a daily basis, thereby resulting in formation of almost one to two liters of urine. However, this amount varies with the amount of water (or fluid) intake and the amount of sweat produced by the body.
•  Though we keep describing kidneys as bean-shaped organs, the beans were named after the organ and not vice versa! Moreover, one of the other urinary system facts is that, if at all one kidney fails to function, the other kidney takes up the entire load of filtration.
•  Urine is almost odorless when it leaves a healthy body. Surprised! Well, another surprising urine fact is that urine is also sterile when it leaves the body. It does contain metabolic wastes, salts and fluids, however, it is devoid of viruses, bacteria and fungi. Once the urine comes outside the body, bacteria in the air converts chemicals present in it to other forms of smelly chemicals like ammonia, etc. So this is how the foul smell of urine comes!
•  Kidneys of the urinary system maintain the amount of fluid balance in the body. Consumption of excess water results in diluted, pale-colored urine and consumption of inadequate amounts of water results in conservation of water by the kidneys, thereby conducing to dark yellow-colored urine.
•  Sometimes people have this urge to urinate shortly after visiting the restroom. Then when they try to urinate, only a little urine comes out. This mostly happens during a bladder or urinary tract infection.
•  Frequent urination is also a sign of pregnancy. The growing uterus applies pressure on the urinary bladder, which causes one to urinate frequently. Moreover, during pregnancy blood flow to the kidneys increases rapidly, thereby resulting in faster filtration and urine formation. About 2 to 4% pregnant women develop urinary infections, which can also be the reason for frequent urination sensation.
•  Urine is often diluted and added to potted plants and plants in gardens. This is because, the adequate urea content in urine is a wonderful source of nitrogen to plants. So if you have a garden, you now know what to do!
•  Have you heard of urine therapy? Well, urine therapy involves application of urine for medical or cosmetic purposes. People apply urine on the skin and even drink urine for medicinal benefits. Don't freak out, they drink their own urine only! Moreover, during wars in historic times, urine was applied on open wounds to destroy bacteria, due to its antiseptic qualities. According to them, the darker the urine, the more effective would be the urine!
•  Urine should normally contain only salts, metabolic wastes and fluids. However, at times sugar is seen to be present in the urine. This is an indication of diabetes. Some other problems associated with the urinary system are polyuria (excess urine production), oliguria (little urine production), dysuria (difficulty and pain in urination), kidney failure, kidney stones, bladder control problems, prostate enlargement and urinary tract infections.
• Most of us have found ourselves in situations where we have had to control our full bladders due to the unavailability of a restroom. However, there is a control limit which shouldn't be exceeded. In the year 2007, Jennifer Strange (age 28) of California participated in a radio station's contest that involved drinking the maximum water without having to visit the restroom. She won the contest, however, was found dead the next day in her house. Doctors confirmed she died of water intoxication. Thus, it is important not to take the importance of the urinary system lightly.

The urinary system is truly a fascinating body system. The way each organ functions, the coordination between different structures, etc. causes one to look at the human body with awe!