Anatomy of the Urinary System

How do the kidneys and urinary system work?

The body takes nutrients from food and converts them to energy. After the body has taken the food components that it needs, waste products are left behind in the bowel and in the blood.

Illustration of the anatomy of the urinary system, front view

The kidney and urinary systems help the body to eliminate liquid waste called urea, and to keep chemicals, such as potassium and sodium, and water in balance. Urea is produced when foods containing protein, such as meat, poultry, and certain vegetables, are broken down in the body. Urea is carried in the bloodstream to the kidneys, where it is removed along with water and other wastes in the form of urine.

READ:   Urinary System: Facts, Functions & Diseases

Other important functions of the kidneys include blood pressure regulation and the production of erythropoietin, which controls red blood cell production in the bone marrow. Kidneys also regulate the acid-base balance and conserve fluids.

Illustration of the anatomy of the kidney

Kidney and urinary system parts and their functions

  • Two kidneys. This pair of purplish-brown organs is located below the ribs toward the middle of the back. Their function is to remove liquid waste from the blood in the form of urine; keep a stable balance of salts and other substances in the blood; and produce erythropoietin, a hormone that aids the formation of red blood cells. The kidneys remove urea from the blood through tiny filtering units called nephrons. Each nephron consists of a ball formed of small blood capillaries, called a glomerulus, and a small tube called a renal tubule. Urea, together with water and other waste substances, forms the urine as it passes through the nephrons and down the renal tubules of the kidney.
  • Two ureters. These narrow tubes carry urine from the kidneys to the bladder. Muscles in the ureter walls continually tighten and relax forcing urine downward, away from the kidneys. If urine backs up, or is allowed to stand still, a kidney infection can develop. About every 10 to 15 seconds, small amounts of urine are emptied into the bladder from the ureters.
  • Bladder. This triangle-shaped, hollow organ is located in the lower abdomen. It is held in place by ligaments that are attached to other organs and the pelvic bones. The bladder’s walls relax and expand to store urine, and contract and flatten to empty urine through the urethra. The typical healthy adult bladder can store up to two cups of urine for two to five hours.
  • Two sphincter muscles. These circular muscles help keep urine from leaking by closing tightly like a rubber band around the opening of the bladder.
  • Nerves in the bladder. The nerves alert a person when it is time to urinate, or empty the bladder.
  • Urethra. This tube allows urine to pass outside the body. The brain signals the bladder muscles to tighten, which squeezes urine out of the bladder. At the same time, the brain signals the sphincter muscles to relax to let urine exit the bladder through the urethra. When all the signals occur in the correct order, normal urination occurs.
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Facts about urine

  • Adults pass about a quart and a half of urine each day, depending on the fluids and foods consumed.
  • The volume of urine formed at night is about half that formed in the daytime.
  • Normal urine is sterile. It contains fluids, salts and waste products, but it is free of bacteria, viruses and fungi.
  • The tissues of the bladder are isolated from urine and toxic substances by a coating that discourages bacteria from attaching and growing on the bladder wall.
Bladder cancer ICD-9: 188.x* Description Tumors of the bladder arise from the epithelial cell membrane lining the bladder interior. These neoplasms are almost always malignant, and they metastasize readily. Bladder tumors are staged according to their depth of penetration. Transitional cell carcinoma is the most common type of bladder cancer in the United States. Etiology The cause of bladder tumors is unknown; however, cigarette smoking is thought to be the predominant cause. Predisposing factors may include exposure to certain types of industrial chemicals. Individuals with chronic cystitis also seem prone to develop bladder tumors. The disease affects men three times more frequently than women and generally occurs between ages 50 and 70. Bladder cancer is the fourth most common cancer in men. Signs and Symptoms Many persons are asymptomatic until advanced stages of the disease. For those presenting with symptoms, however, painless, gross hematuria is the most common indicator. Le...
Acute Tubular Necrosis ICD-9: 584.5 Description Acute tubular necrosis is the rapid destruction or degeneration of the tubular segments of nephrons in the kidneys. The disease is characterized by a sudden deterioration in renal function, with resulting accumulation of nitrogenous wastes in the body. Impaired or interrupted renal function from acute tubular necrosis is considered reversible. Etiology The majority of cases of acute tubular necrosis are due to renal ischemia, or the interruption or impairment of blood flow in and out of the kidneys. This disease is the most common cause of acute renal failure in critically ill persons. Although there can be numerous causes for such impairment, renal ischemia leading to acute tubular necrosis is most frequently produced by severe bodily trauma or as a complication following surgery. The renal tubules also can be damaged in other ways. Acute tubular necrosis may be toxin induced (as a result of exposure to solvents, heavy metals, or certain medication...
Polycystic Kidney disease ICD-9: 753.12 Description Polycystic kidney disease is a developmental defect of the collecting tubules in the cortex of the kidneys. Groups of tubules that fail to empty properly into the renal pelvis slowly swell into multiple, grapelike, fluid-filled sacs or cysts. The pressure from the expanding cysts slowly destroys adjacent normal tissue, progressively impairing kidney function. Both kidneys are usually affected and are grossly enlarged. Polycystic kidney disease is one of the most common hereditary diseases in the United States, affecting more than 600,000 people. It is the cause of nearly 10% of end-stage renal disease and affects men, women, and all races equally. Etiology There are two forms of the disease, each due to a genetic defect. The more common adult form, usually manifested during midlife, is an autosomal dominant defect. The much less common infant and childhood forms, manifested at birth or during childhood, are autosomal recessive defects. The followin...
Kidney Stones What are kidney stones? Kidney stones, or renal calculi, are solid masses made of crystals. Kidney stones usually originate in your kidneys. However, they can develop anywhere along your urinary tract, which consists of these parts: kidneys ureters bladder urethra Kidney stones are one of the most painful medical conditions. The causes of kidney stones vary according to the type of stone. Types of kidney stones Not all kidney stones are made up of the same crystals. The different types of kidney stones include: Calcium Calcium stones are the most common. They’re often made of calcium oxalate (though they can consist of calcium phosphate or maleate). Eating fewer oxalate-rich foods can reduce your risk of developing this type of stone. High-oxalate foods include: potato chips peanuts chocolate beets spinach However, even though some kidney stones are made of calcium, getting enough calcium in your diet can prevent stones from forming. U...
Urinary System: Facts, Functions & Diseases The urinary system, also known as the renal system, produces, stores and eliminates urine, the fluid waste excreted by the kidneys. The kidneys make urine by filtering wastes and extra water from blood. Urine travels from the kidneys through two thin tubes called ureters and fills the bladder. When the bladder is full, a person urinates through the urethra to eliminate the waste. The urinary system is susceptible to a variety of infections and other problems, including blockages and injuries. These can be treated by a urologist or another health care professional who specializes in the renal system. Description of the urinary system The urinary system works with the lungs, skin and intestines to maintain the balance of chemicals and water in the body. Adults eliminate about 27 to 68 fluid ounces (800 to 2,000 milliliters) per day based on typical daily fluid intake of 68 ounces (2 liters), National Institutes of Health (NIH). Other factors in urinary system function include fluid ...