Urinary System

Functions

1. Waste Removal
The urinary system is a complimentary waste removal system to that of the digestive system.
2. Homeostasis 
The Urinary system is important in also changing levels of various minerals, vitamins, and nutrients in the body, as well as maintaining a certain pH. 

Kidneys

The kidney's are one of the most waste-filtering systems in the body. These two small organs that lie around the lower back of humans are especially important. A large amount of blood is diverted from the heart to the kidneys, so almost all blood passes through a kidney several times a day. Here, the blood is "washed" of any toxins and harmful chemicals or residue before being sent back to the heart. The kidneys also function in homeostasis, changing electrolyte levels to suit the body's needs. 

Urethra

Another simple organ, the urethra simply takes urine from the bladder and expels it. 

Ureters

Each kidney is connected to a thin tube known as a ureter. Once the kidney's have collected their waste, they send it down their respective ureters in liquid form where it all collects in the bladder. 

Bladder

The bladder is nothing past a storage facility. It collects waste from the ureters in the form of urine and releases it all when the time comes to finally expel all the waste.

Urine

The namesake of the urinary system is the main reason it exists. The urinary system is primarily a waste-removal system and urine is the waste. This waste is anything in the body that could prove toxic. It is mixed in with large amounts of water to help it through the system and expelled as urine. The concoction is in fact around 95% water - the remaining 5% is the remaining wastes of everyday function. Various toxins can include random excess particles of carbon monoxide or other gases, and often includes nitrogenous wastes, or urea, that arise due to everyday interactions with amino acids. Many animals actually have a similar system, but expel their urea as a solid uric acid.