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Bladder Anatomy & Physiology

Female Urological System:

In both sexes, the bladder is a hollow organ located within the pelvis (unless it is full and distended.)  It consists primarily of smooth muscle protected on the interior surface by a two flexible stretchy layers, the submucous, and the mucous coats - which serve to protect the muscle layer from the acids, salts, and toxins in urine. 

The outside of the bladder is encased in and supported by a layer of connective tissue called fascia.

The ureters are thin, stretchy tubes which lead from the bladder to the kidneys, and the urethra is a much shorter tube which leads from the bottom of the bladder, to the external opening known as the urethral orifice.  The urethra contains mucous glands which secrete protective mucous into the urethral canal.  In females, this tube is fairly short, about 4 cm. (or slightly less than 2 inches) long.

The urethral orifice (external opening) is located anteriorly above the vaginal opening, but can vary a little from person to person, based on anatomical differences.  The urethra in females is designed to carry only urine and mucous secretions.  At the point where the bladder empties into the urethra (the bladder neck) there is an internal urethral sphincter, or a ring of muscular tissue.

The process of voiding is quite complicated, even in normal, non-dysfunctional circumstances.  The important detrusor muscle, the perineal muscles (bottom of the pelvic floor), the muscles of the abdominal wall, the muscles of the urethral sphincters, and even the diaphragm are involved in the process of building pressure within the bladder and then relaxing once the nerves have succeded in transmiting the urge to void.

Male Urological System:

There are obvious differences in the anatomy of the male urological system.   In males, the urethra is much longer, and is made up of three parts:  the prostatic, the membranous, and the spongy.  Males also have a donut-shaped organ called the prostate gland surrounding the urethra.  It is this gland that the section of the urethra called the prostatic urethra must pass through, which can cause problems later in life as the prostate gland enlarges and can constrict the flow of urine.

The membranous section of the male urethra passes through the urogenital diaphragm, and through the ring of muscular tissue known as the external urethral sphincter.

The final section of the male urethra is the spongy section that passes through the length of the penis to the urethral meatus, or external orifice.  In males, the urethra serves more than one function.  Both urine and seminal fluid from the reproductive organs pass through this tube.  This requires great elasticity to open up and accomodate a larger flow during both urination and ejaculation.

Beyond this simplified description, it is important to realize that a great  many nerves and accessory muscles are involved in the process of bladder filling, and emptying in both sexes.  These nerves are part of both the parasympathetic and sympathetic nervous systems.  Some nerves control voluntary muscles, and some nerves control involuntary muscles.