The body excretes urine which is a liquid waste material. The group of organs which produce, store and release urine are known as the renal system, the excretory system or the urinary system. These organs include the kidneys, bladder, ureters and urethra.
Most of the renal system’s functions are carried out by the kidneys which are at the lower back part of the abdomen. Besides passing the urine into the ureters, the kidneys help to regulate blood pressure, they regulate the body’s pH balance and also the balance the amounts of electrolytes, mostly sodium and potassium in the body.
The ureters are small muscular tubes which connect the kidneys to the bladder. The muscles of the ureters exert a pressure to force urine out of the kidneys and into the bladder. The ureters ensure that urine cannot flow back into the kidneys. When they do not function, the backward flow of urine is known as reflux.
The bladder is a muscular, hollow balloon placed in the pelvic area. It collects and stores urine. The muscles and balloon structure allow the bladder to hold urine amounting from half a cup to just a little less than two cups. When a feeling of fullness is felt in the bladder, it means that the urine needs to be excreted. The urine then passes into the urethra, which is the final part of the renal system. The urethra is a tube connected to the genitals and transports the urine to the exit, an opening in the genitals.