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At birth the structures of the urinary system are fully developed and function under the automatic control of the nervous system. The newborn’s kidneys filter blood and make urine. The bladder collects the urine and, when it fills to a point that triggers the micturition reflex, it empties to drain urine via the urethra to outside the body. Voluntary control over urination develops between three and five years of age, the rite of passage from babyhood to childhood. The urinary system typically then functions at a steady level for decades, unless disease alters its structures (notably the kidneys).
Changes in the Kidneys and Bladder
Beginning around age 40 the number, size, andefficiency of nephrons, the filtering units of the kidneys, begins to diminish. At birth each kidney contains a million or more nephrons. By age 70 the kidneys have lost about 30 percent of the nephrons they contained at birth. They are smaller overall in size and take longer to filter the blood that flows through them. They may allow more water to enter the urine and keep more electrolytes in the blood circulation. The imbalance, even when slight, often affects blood pressure and other vital functions and increases the risk for dehydration.
Other changes in the body often affect the kidneys as well as other structures of the urinary system. With aging fibrous tissue throughout the body begins to lose elasticity, becoming more rigid. This reduced flexibility can harden and narrow the blood vessels that supply the kidneys, slowing blood flow into the kidneys and through the nephrons. It also diminishes the bladder’s ability to distend (expand), decreasing bladder capacity. Age-related changes in nerve and brain function also slow the micturition reflex, allowing the bladder to become more full before triggering the urge to urinate. These changes can result in urinary urgency and urinary frequency.
The Effects of Other Changes and Health Conditions
Age-related changes in the reproductive system-menopause in women and benign prostatic hyperplasia (bph) in men-affect the urinary system as well. The normal and usually harmless enlargement with aging of the prostate gland in men can constrict the urethra, interfering with the flow of urine during urination. Relaxation of the pelvic structures that accompanies the decline of the levels of estrogens in women who are past menopause affects the woman’s ability to control the flow of urine, allowing problems such as stress incontinence (urine leakage with coughing, sneezing, or laughing). As well, stretching and tearing of the pelvic muscles and ligaments that may have occurred during pregnancy and childbirth may weaken these structures, allowing the bladder to sag and pressure the vagina (cystocele).
Hypertension (high blood pressure) and diabetes, two conditions that become increasingly common with advancing age, are particularly hazardous to the kidneys and between them account for about 80 percent of renal failure (acute and chronic) and end-stage renal disease (esrd). Early and appropriate treatment for these conditions can significantly slow their actions on the kidneys, highlighting the importance of routine health screening for them. The risks for bladder cancer, renal cancer, nephropathy, nephrolithiasis (kidney stones), and urolithiasis (bladder stones) also increase with age.
Measures to Maintain Urinary Health
Though it is not possible to prevent many of the health conditions affecting the urinary system that become more common with age, there are preventive lifestyle measures that can help maintain urinary health. These include
- drink a minimum of 8 to 12 eight-ounce glasses of water daily, more when it is hot or with exercise (urine should be colorless or slightly yellow)
- get blood pressure checked by a health-care provider at least yearly
- get checked for diabetes regularly
- urinate when the urge occurs and empty the bladder completely when urinating
- minimize use of over-the-counter products containing acetaminophen or nonsteroidal anti-inflammatory drugs (nsaids)
- do not smoke (cigarette smoking accounts for 50 percent of bladder cancers)
Maintaining a healthy weight, nutritious EATING HABITS, and daily physical exercise are important for good health overall. People who have diagnosed hypertension or diabetes should strive to maintain the best possible control over these conditions through appropriate lifestyle measures and by taking medications as prescribed.
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