The bladder is the part of the urinary tract that collects and stores urine via the ureters from the kidneys. The bladder is a muscular, elastic organ which varies in size, shape and position, and it is depending from degree of filling. When empty, the adult urinary bladder is located in the lesser pelvis. As the bladder fills, it enters the grater pelvis. In some individuals, a full bladder may ascend to the level of umbilicus. In most adults, the bladder capacity is around 600 mls of urine. It passes up to 2L of urine a day. At the end of urination the bladder of a healthy adult contains almost no urine. The bladder has an apex, body, fundus and neck. The bladder has four surfaces – superior, two inferolateral and posterior.
In male urine is expelled from bladder through the urethra, which passes through the prostate gland and travels through the penis. The urinary sphincter, which holds back the urine, is largely included into the prostate. The vasa deferentia and seminal vesicles lie behind the bladder. Behind them lies the rectum, separated from the bladder by the thin sheet of tissue called the fascia of Denonvilliers.
The mucosa layer is the innermost layer of the bladder. It is multilayered transitional epithelium, which is able to stretch significantly to accommodate urine. The bladder mucosa is coated by a protective layer of molecules called the glycosaminoglycan (GAG) layer.
The submucosa is the surrounding of the mucosal layer. This layer is rich of connective tissue with thin and thick elastic fibers. The blood vessels and nervous supports and controls the surrounding tissue layers. The bladder submucosa, or lamina propria, overlies the detrusor muscle.
The muscle is a main part of the bladder wall, which composed of three different layers (external, median and internal) and commonly referred to as a detrusor. The muscles provide the urinary bladder with its ability to expand, contract and expel urine from the body. They also form the internal urethral sphincter. Urethral sphincter is a ring of muscle that surrounds the urethral opening and holds urine in the urinary bladder. During urination, the sphincter relaxes to allow urine to flow into the urethra.
The serosal layer is the outermost layer of the bladder. The dome of the bladder is covered by peritoneum – a thin bag of tissue holding the intestines and other organs.