Anatomy and Function
The bladder is a hollow balloon-shaped mostly muscular organ that stores urine until ready for release. A thin surface layer called the urothelium lines the inside of the bladder. Next is a layer of loose connective tissue called the lamina propria. Covering the lamina propria is the bladder muscle, covered on the outside by fat.
More than 90 percent of all bladder cancers originate in the urothelium. The majority of diagnosed bladder tumors are confined to the urothelium or the lamina propria and have not invaded the bladder muscle.