Anatomy

The urinary tract consists of the kidneys, the ureters, the bladder, and the urethra. The urinary tract is lined with transitional cell urothelium from the renal pelvis to the proximal urethra. Transitional cell carcinoma (also known as urothelial carcinoma) can develop anywhere along this pathway.

This module is specific to bladder sites (excludes kidney, renal pelvis, urethra, and ureters).

The empty bladder is about the size and shape of a pear. It is located in the lower pelvic cavity. Urine drains from the kidneys into the bladder through the ureters. From the bladder, urine is excreted through a tube called the urethra. In women, this tube is about 1.5 inches long and exits the body at the upper aspect of the vaginal opening. In men the urethra is about 8 inches long and passes through the penis, opening at its tip.

The bladder has a muscular wall that allows it to expand so that it can store urine made by the kidneys and allows it to shrink in order to squeeze urine out of the body. There are two kidneys, one on each side of the backbone, above the waist.

The bladder and kidneys work together to remove toxins and wastes from the body through urine.

1. Tiny tubules in the kidneys filter and clean the blood.
2. These tubules take out waste products and make urine.
3. The urine passes from each kidney through a long tube called a ureter into the bladder.
4. The bladder holds the urine until it passes through a tube called the urethra and leaves the body.

Diagram of bladder and kidneys. Source: © 2010 Terese Winslow LLC.

Updated: April 22, 2025