Micturition is the process of excreting excess fluid and substances that have potential harm to the body through the acts of urination and voiding. The renal system is involved in micturition. The kidneys filter excess water and waste products to produce urine. The ureters connect each kidney to the urinary bladder for storage until the time for micturition. When urinating, urine flows from the bladder through the urethra and out of the body from the urethra opening.
Micturition is supposed to be a somewhat voluntary reflex. The bladder sends signals through the spinal cord to the brain and creates and urge to urinate. The bladder sends signals when its walls have been stretched and it cannot accumulate more fluid or when it is convenient to urinate. At urination, the brain then commands the bladder’s muscular walls to contract so that the urine is expelled from the body through the urethra.
In young and old people, or some people with spinal injuries or brain damage, the micturition reflex lacks the voluntary aspect involved in someone ensuring that they are in control of where and how they urinate. Other micturition problems include urinary retention when a bladder cannot be emptied completely; the inability to hold back urine, urinary incontinence; and more than normal urination urges, urinary frequency. Anuria occurs when there is no urine output and oliguria is when there is very little urine being excreted. Problems in micturition are often caused by prostrate problems in men, pregnancy in women and urinary tract infections.