Urinary system anatomy and physiology review

The urinary system is responsible for the production and elimination of urine when a type of waste called urea is removed from the blood. Urea is produced when protein-containing foods are broken down in the body. Urea is carried in the bloodstream to the two kidneys, where urine is formed. The two ureters, the urinary bladder, and the urethra, are responsible for the elimination of urine. Figure illustrates the urinary system in relationship to the body, and Figure illustrates the interior and exterior features of the urinary system organs.

The urinary system

FIGURE. The urinary system

Frontal section of the right kidney showing internal structures and blood vessels

FIGURE. (A) Frontal section of the right kidney showing internal structures and blood vessels. (B) Magnified section of the kidney shows several nephrons. (From Scanlon, VC, and Sanders, T: Essentials of Anatomy and Physiology, ed 5. FA Davis, Philadelphia, 2007, p 422, with permission.)

The kidneys, each about the size of a fist, help to regulate the water, electrolyte (ionized salt), and acid-base content of the blood, and they selectively filter the waste products of metabolism.

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They also play an important role in regulating blood pressure. Each kidney contains more than 1 million nephrons, which are the principal filtering units of the kidney. Each nephron houses a ball of tiny blood capillaries called the glomerulus and a renal tubule. It is here that the three-part process of selective filtration of wastes, reabsorption of vital minerals and fluid, and secretion of waste products and other substances takes place. As urine is formed, it passes through the nephrons into the renal tubules of the kidneys.

Nephron with associated blood vessels

FIGURE. Nephron with associated blood vessels

From the kidneys, urine travels into the ureters, thin tubes about 8 to 10 inches in length, on its way to the urinary bladder. Small amounts of urine drip into the urinary bladder about every 12 seconds. The urinary bladder is a balloon-shaped muscular organ that stores urine until it is emptied. It can hold about 16 ounces of urine for 2 to 5 hours. Nerves in the urinary bladder indicate when it should be emptied. Sphincter muscles keep urine from leaking into the urethra too soon and relax when it is time to urinate.

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It is worth emphasizing the reabsorption process of the kidneys’ nephrons. Were it not for this process, the body would rapidly be depleted of its fluid. Typically, only 1% of the fluid passing through a nephron is excreted as urine.

A routine diagnostic test for suspected urinary disease is a urinalysis, which includes testing the specific gravity; pH; and presence of protein, blood, sugar, and ketones. It includes a microscopic examination for the presence of white blood cells (WBCs) and red blood cells (RBCs), casts, bacteria, and crystals. Normal urine is amber in color with a slightly acid reaction, has a peculiar odor, and frequently deposits a precipitate of phosphates when fresh. The specific gravity varies from 1.005 to 1.030. The greater the rate of urine excretion, the lower is the specific gravity. Refer to Table, Significance of Changes in Urine, throughout the chapter, noting possible abnormalities and their significance to the disease in question.

Table. Significance of Changes in Urine

Significance of Changes in Urine

Renal cell carcinoma or Kidney cancer ICD-9: 189.x Description Renal cell carcinoma (RCC), also known as renal cell adenocarcinoma, is by far the most common type of kidney cancer, accounting for 90% of kidney cancers. RCC usually grows as a single mass within the kidney but can be found in more than one part of the kidney or in both kidneys. It occurs most often in individuals over age 40. Etiology The cause is essentially unknown; however, risk factors include smoking, obesity, hypertension, long-term dialysis, and exposure to chemicals and irritants, such as asbestos or cadmium in the workplace. Signs and Symptoms Symptoms may include hematuria, flank or side pain that does not go away, a lump or mass palpated in the side or abdomen, weight loss, and fever. Some clients report feeling listless and not well. Diagnostic Procedures A complete physical examination may reveal an enlarged mass. BUN and creatinine levels are checked. A CT scan using contrast media is often used in diagnosis, as is the i...
Urinary Tract Infection: Symptoms, Diagnosis, and Treatment What is a UTI? A urinary tract infection (UTI) is an infection from microbes. These are organisms that are too small to be seen without a microscope. Most UTIs are caused by bacteria, but some are caused by fungi and in rare cases by viruses. UTIs are among the most common infections in humans. A UTI can happen anywhere in your urinary tract. Your urinary tract is made up of your kidneys, ureters, bladder, and urethra. Most UTIs only involve the urethra and bladder, in the lower tract. However, UTIs can involve the ureters and kidneys, in the upper tract. Although upper tract UTIs are more rare than lower tract UTIs, they’re also usually more severe. UTI symptoms Symptoms of a UTI depend on what part of the urinary tract is infected. Lower tract UTIs affect the urethra and bladder. Symptoms of a lower tract UTI include: burning with urination increased frequency of urination without passing much urine increased urgency of urination bloody urine cloudy urine ...
Nephrotic syndrome ICD-9: 581.9 Description Nephrotic syndrome is a condition or a complex of signs and symptoms (syndrome) of the basement membrane of the glomerulus. (The basement membrane surrounds each of the many tiny capillaries comprising a glomerulus.) The disease is characterized by severe proteinuria, often to the extent that the body cannot keep up with the protein loss, which is known as hypoalbuminemia. The disease is further characterized by hyperlipemia (excessive levels of fatlike substances called lipids in the blood), lipiduria (lipids in the urine), and generalized edema. Etiology Nephrotic syndrome may result from a variety of disease processes having the capacity to damage the basement membrane of the glomerulus. Between 70% and 75% of the cases of nephrotic syndrome result from some form of glomerulonephritis. The syndrome also may arise as a consequence of diabetes mellitus, systemic lupus erythematosus, neoplasms, or reactions to drugs or toxins. The disease is occasio...
8 Signs and Symptoms of Kidney Stones What are kidney stones? Kidney stones are hard collections of salt and minerals often made up of calcium or uric acid. They form inside the kidney and can travel to other parts of the urinary tract. Stones vary in size. Some are as small as the period at the end of this sentence — a fraction of an inch. Others can grow to a few inches across. Some kidney stones can become so large they take up the entire kidney. A kidney stone forms when too much of certain minerals in your body accumulate in your urine. When you aren’t well hydrated, your urine becomes more concentrated with higher levels of certain minerals. When mineral levels are higher, it’s more likely that a kidney stone will form. About 1 out of every 11 people in the United States will get a kidney stone. Stones are more common in men, people who are obese, and those who have diabetes Smaller kidney stones that remain in the kidney often don’t cause any symptoms. You might not notice anything is amiss until the ...
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 ...