Anatomy of the Bladder

The bladder is a hollow organ in your lower abdomen. It’s the storage place for urine. This is the liquid waste that’s made by the kidneys. Urine flows from each kidney through a tube called a ureter. The ureters carry urine into the bladder. The urine stays in the bladder until you urinate.

An outer layer of muscle surrounds the inner lining of the bladder. When the bladder is full, the muscles in the bladder wall can be tightened to allow urination. Urine leaves the bladder through another tube. This is called the urethra. After you urinate, the bladder shrinks in size.

The bladder is made of several layers. These include the following:

  • Urothelium or transitional epithelium: This is the layer of cells that lines the inside of the kidneys, ureters, bladder, and urethra. Cells in this layer are called urothelial cells or transitional cells.

  • Lamina propria: This is the next layer down. It’s under the urothelium. It’s a type of connective tissue.

  • Muscularis propria: This is the next layer. It’s under the lamina propria. It is muscle tissue.

  • Fatty connective tissue: This separates the bladder from other organs.

Superficial bladder cancer affects only the lining of the bladder. This is the transitional epithelium. Invasive bladder cancer goes into deeper layers of the bladder wall.