The urinary system produces urine

and conducts it to outside the body.

As the kidneys produce urine, they

carry out four functions: excretion

of metabolic wastes, maintenance

of water-salt balance, maintenance

of acid-base balance, and secretion

of hormones.

Organs of the Urinary System

Kidneys: paired organs located near the small of the back in the lumbar region on wither side of the vertebral column

Ureters: extend from the kidneys to the bladder, are small, muscular tubes about 25 cm long and 5 mm in diameter

Urinary bladder: located in the pelvic cavity, below the parietal peritoneum and just posterior to the pubic symphysis

Urethra: a small tube that extends from the urinary bladder to an external opening

URINATION

As the bladder fills with urine, sensory impulses go to the spinal cord and then to the brain. The brain can override the urge to urinate. When urination occurs, motor nerve impulses cause the bladder to contract and an internal sphincter to open. Nerve impulses also cause an external sphincter to open.

A sagittal section of a kidney shows that many branches of the renal artery and renal vein reach inside a kidney. Removing the blood vessels shows that a kidney has three regions. The renal cortex is an outer, granulated layer that dips down in between a radially striated inner layer called the renal medulla. The renal medulla consists of cone-shaped tissue masses called renal pyramids. The renal pelvis is a central space, or cavity, that is continuous with the ureter.

Reabsorbed Filtrate Components Nonreabsorbed Filtrate Components

Most water Some water

Nutrients Much nitrogenous waste

Required salts (ions) Excess salts (ions)

Problems with kidney function

Urinalysis is an examination of the physical, chemical, and microscopic properties of the urine. This is done to help determine the state of the body. Many types of illnesses, especially diabetes, hypertension, and inherited conditions, cause progressive renal disease and renal failure. Some of the things are called urethritis, cystitis, and pyelonephritis.

Effects of Aging

Urinary disorders are significant causes of illness and death among the elderly. With increasing age, the kidneys decrease in size and have significantly fewer nephrons. Kidney stones occur more frequently with age, possibly as a result of improper diet. Involuntary loss of urine is another effect of aging.

Dangers

The idea that smoking can be harmful to your urinary tract may seem a bit strange at first, since your lungs and your kidneys are nowhere near each other in your body. But because of the way that substances circulate through your blood, toxic substances from cigarette smoke can reach your urinary tract quite easily, and they may be damaged as a result.

Cystitis: Inflammation of the urinary bladder caused by a bacterial infection

Kidney stones: Large accumulations of calcium salt crystals from urine that may form in the kidneys

Pyelonephritis: Inflammation of the kidneys caused by a bacterial infection.

Warnings

Bladder cancer develops when cells lining the urinary bladder become abnormal and grow uncontrollably, forming tumors. It is the fifth most common cancer in the United States. The disease is three times more common in men than woman. Most cases of bladder cancer are found in people who are fifty to seventy years old.

Urethritis: Inflammation of the urethra caused by a bacterial infection

Urinary incontinence: Involuntary and unintentional passage or urine.

definition

What does the urinary system do?

The urinary system allows for the body to keep the chemicals and water in you balanced by working with the lungs, skin, and intestines -- all of which excrete wastes. The urinary system consists of two kidneys, two ureters, the bladder, two sphincter muscles, and the urethra. When we eat, the body takes nutrients from the food and uses them to provide energy.

The job of the urinary system is to excrete the waste product urea from the blood; urea is produced when foods containing protein are broken down in the body. Urea is carried in the bloodstream to the kidneys, which remove urea from the blood through nephrons, which are tiny filtering units. Urea, water, and other waste substances together form urine as it passes through the nephrons. From the kidney, two tubes called ureters transport the urine to the bladder. The bladder is a hollow muscular organ whose job it is to store urine until you are ready to go to the bathroom, at which time the urine passes outside the body via the urethra. Muscles called sphincters keep the urine from leaking.

Why is the urinary system important?

Without the urinary system, the waste product urea wouldn't be able to be exreted and would build up inside the body.

explanation

If you smoke a cigarette, harmful substances from the smoke are absorbed from your lungs into your bloodstream. These substances then travel through your bloodstream to all parts of your body, including your kidneys. It is the job of the kidneys to filter waste products and toxic substances out of the blood, so that they can be removed from the body. The kidneys filter out many tobacco smoke components and collect them in the urine. The urine -- now filled with harmful substances -- then goes into the bladder before it is excreted from the body. Thus, both the kidney and bladder are exposed to harmful substances from cigarette smoke, and they may be damaged as a result.