Female urinary tract
Male urinary tract
The bladder and kidneys are part of the urinary system. These are the organs that make, store, and pass urine. When the urinary system is working well, the kidneys make urine and move it into the bladder. The bladder is a balloon-shaped organ that serves as a storage unit for urine. It is held in place by pelvic muscles in the lower part of your belly.
When it is not full of urine the bladder is relaxed. Nerve signals in your brain let you know that your bladder is getting full. Then you feel the need to urinate. The brain tells the bladder muscles to squeeze (or "contract"). This forces the urine out through your urethra, the tube that carries urine from your body. Your urethra has muscles called sphincters. They help keep the urethra closed so urine doesn't leak before you're ready to go to the bathroom. These sphincters open up when the bladder contracts.