The renal system is a group of organs which work together to produce, store, and release urine. Urine is the liquid waste material excreted from the body. The organs which work together to form the renal system include the kidneys, bladder, ureters, and urethra. The renal system is also known as the urinary system or the excretory system.

The kidneys are a vital part of the renal system. They are located in the back portion of the abdominal cavity, with one kidney on either side. Perhaps the most well-known function of the kidneys is to transport urine into the tubes known as ureters before the urine exits the body. However, the kidneys also have several other important functions, such as helping to regulate blood pressure. They also work to regulate the pH balance in the human body as well as the balance of electrolytes such as sodium and potassium.

The next part of the renal system is the bladder, sometimes referred to as the urinary bladder. The bladder is shaped much like a muscular, hollow balloon and sits in the pelvic area of the body. The primary function of the urinary bladder is to collect and store the urine which has left the kidneys. Once the bladder starts to becomes full, the urine begins to leave the bladder and pass into the ureters.

The ureters, another part of the renal system, are small tubes made of muscle. These structures are attached at one end to the kidneys and to the bladder at the other. The ureters use a small amount of pressure to gently force or push urine from the kidneys to the bladder and then from the bladder to the urethra on its way out of the body. Another role of the muscular nature of the ureters is to prevent urine from backing up and going back into the kidneys once it has passed into the bladder, a disorder which would be known as reflux.

The urethra is the final portion of the renal system. This structure is a hollow tube which is connected to the ureters and passes through the genitals, finally exiting the body. The urethra passes through the penis in males and is responsible for transporting both urine and semen. This tube is significantly shorter in females and stops just above the opening to the vagina. An external muscle known as the urethral sphincter helps to control the action of voluntary urination.