Bladder tumour. Illustration of a tumour (pink, centre right) inside a sectioned view of the bladder. Bladder cancers usually arise in the internal lining of the bladder. Here, the tumour has penetrated the detrusor muscle layer in the wall of the bladder. Treatment involves excision of affected tissues, chemotherapy and radiotherapy. The ureters (upper left and upper right) bring urine into the bladder from the kidneys. The urine leaves the body through the urethra (bottom). Also seen is the prostate gland (lower centre) at the base of the bladder and wrapped around the urethra. The membrane seen lying across the top of the bladder is part of the peritoneum.