Normally, the average person urinates no more than six to eight times each day, and does not have to get up at night to use the bathroom. When a person needs urinate more than once every couple of hours during the day, or get up several times during the night, something is probably wrong.
After urine is produced by the kidneys
, it flows down the ureters into the bladder. The bladder is a hollow, balloon-like organ, most of its wall being made of muscle. As the bladder fills, the muscle relaxes so that the bladder expands and holds urine. During urination, the bladder muscle contracts to squeeze out the urine. The urethra is the tube through which urine passes from the bladder to the outside. The urethra has a muscle – the sphincter – which is completely separate to the bladder muscle. The sphincter normally stays closed and makes a seal to keep urine from leaking. During urination, the sphincter opens and lets urine pass.
The bladder and urethra have a specialized lining called the epithelium. The epithelium forms a barrier between the urine and the bladder muscle. The epithelium also helps to keep bacteria
from sticking to the bladder, so it helps to prevent bladder infections
Causes and Development
Common causes of frequent urination include:
Added to these possible causes is the natural process of aging: As we get older, the muscle of the bladder loses elasticity and tone. As a result, the bladder's capacity can be reduced by almost 50%, causing more frequent urination, and may empty less completely. The warning period between the urge and actual urination is also shortened or even lost as one ages. In addition, muscular disability, spinal cord effects on the bladder muscle, tumors
, infection, or anatomic damage to the sphincters and/or bladder neck may cause incontinence
in advancing age. Other risks for incontinence in old age include chronic disease, cognitive impairment, medications, smoking, pelvic
muscle weakness, low fluid intake and environment.