The excretory system serves the purpose of waste disposal for the body. The excretory system excretes toxins, excess water, and other solutes. In addition the excretory system regulates blood pressure, metabolism, and blood composition and volume. Some of the major organs in the excretory system are the kidneys, ureters, bladder and urethra. The interstitial waste is drained to the iliac node. The excretory system receives its food and oxygen from the iliac and renal arteries and its wastes leave through the renal and hypogastric veins.

The kidney is made up of tiny units called nephrons. The nephrons do three things, the secrete, they filter and they re-absorb. The kidney first filters the blood, removing toxins and other unneeded wastes. After the blood has been filtered it is reabsorbed, the waste that has been filtered out is secreted as urine through a tube called the ureter.

The ureters(one for each kidney) carry the urine from the kidneys by peristaltic contractions. The ureters empty into the urinary bladder.

The urinary bladder is a hollow organ. Its walls are made of muscle and it expands and contracts due to its contents. When full is spherical, when empty it is like a piece of muscle. The urinary bladder dumps the urine into the urethra.

The urethra is the last step in the urinary, or excretory system. The urethra receives the urine from the urinary bladder and is assigned with the job of disposing of it. In females the urethra empties between the clitoris and vaginal opening.