Download The Urinary System - Marshall Middle

(Students: Bolded, italicized, and underlined sections will be on the exam)
The Urinary System:
I. Function of the System: The function of the urinary system is to rid the blood
stream of salt, water, and other wastes. Other functions include making sure your
body is balanced with the amount of salt and water. This system also helps to
regulate blood pressure.
II. The Main Parts of the System:
The major parts of this system include the kidneys, ureter, bladder, and urethra.
A. The Kidneys: The two kidneys are located at the backbone just above your
waist. The main function of the kidneys is to filter waste products from blood.
Although a normal person has two kidneys, they only need one to survive. The
kidneys receive blood from the aorta, filter it, and send it back to the heart with
the right balance of chemicals and fluid for use throughout the body. There are
miniature ‘blood filters’ inside your kidney called nephrons. The kidneys have
many jobs besides the filtering of the blood. These jobs include regulating
blood pressure, regulating salt balance, and controlling water balance.
Without the kidneys, your body would have too much` water, salt, and other
wastes.
1. The Nephrons: The nephrons are small filtering units inside the kidneys.
The nephrons remove excess water, salts, and urea from the blood. Urea is
a nitrogen-based waste which is made when proteins are broken down. All
this waste is turned into urine. Urine is made from salt, water, and urea.
Doctors can use a urine test ensure sure your kidneys and other organs are
working.
B. The Urinary Tract: The urine created by the kidneys is moved out of the body
via the urinary tract. The urinary tract include the ureters, bladder, and urethra.
1. Ureters: The ureters carry the urine from the kidneys to the bladder.
2. Bladder: The urinary bladder is a sac that holds the urine until it travels
through the urethra. The urinary bladder can hold about half a liter of
urine at one time.
3. Urethra: The urethra is the final tube that releases the urine wastes out
from the body.
III. Interactions With Other Systems:
The endocrine system interacts with every system, since it protects every cell in
every organ system from harmful organisms. Also, it helps to regulate fluid levels
throughout the body. Some examples of systems that directly interact with the
system include:
• The Circulatory System: The blood contains the cellular wastes for the kidneys
to filter out.
• The Nervous System: The nervous system controls the kidneys.
IV. Some Disease and Disorders:
• Urinary Tract Infection: Urinary tract infection (UTI) is a common infection that
usually occurs when bacteria enter the opening of the urethra and multiply in the
urinary tract. The urinary tract includes the kidneys, ureters, bladder, and urethra.
The special connection of the ureters at the bladder help prevent urine from
backing up into the kidneys, and the flow of urine through the urethra helps to
eliminate bacteria. Men, women, and children develop UTIs. Most infections arise
from one type of bacteria, Escherichia coli (E. coli), which normally lives in the
colon. In most cases, bacteria first begin growing in the urethra. An infection
limited to the urethra is called urethritis. From there bacteria often move on to the
bladder, causing a bladder infection (cystitis). If the infection is not treated
promptly, bacteria may then go up the ureters to infect the kidneys
(pyelonephritis). Microorganisms called Chlamydia and Mycoplasma may also
cause UTIs in both men and women, but these infections tend to remain limited to
the urethra and reproductive system. Unlike E. coli, Chlamydia and Mycoplasma
may be sexually transmitted.
• Kindey Stones: A kidney stone can develop when certain chemicals in your urine
form crystals that stick together. The crystals may grow into a stone ranging in size
from a grain of sand to a golf ball. Small stones can pass through the urinary
system without causing problems. However, larger stones might block the flow of
urine or irritate the lining of the urinary tract. Most stones form in the kidney.
Some travel to the ureter or bladder. Most stones (70 to 80 percent) contain mainly
calcium oxalate crystals. A smaller number are uric acid stones or cystine stones.
Cystinuria and hyperoxaluria are two other rare, inherited metabolic disorders that
often cause kidney stones. In cystinuria, too much of the amino acid cystine, which
does not dissolve in urine, is voided. This can lead to the formation of stones made
of cystine. In patients with hyperoxaluria, the body produces too much of the salt
oxalate. When there is more oxalate than can be dissolved in the urine, the crystals
settle out and form stones. Absorptive hypercalciuria occurs when the body
absorbs too much calcium from food and empties the extra calcium into the urine.
This high level of calcium in the urine causes crystals of calcium oxalate or calcium
phosphate to form in the kidneys or urinary tract. Other causes of kidney stones
are hyperuricosuria (a disorder of uric acid metabolism), gout, excess intake of
vitamin D, and blockage of the urinary tract. Certain diuretics (water pills) or
calcium-based antacids may increase the risk of forming kidney stones by
increasing the amount of calcium in the urine.
• Polycystic Kidney Disease (PKD) is a genetic disorder characterized by the growth
of numerous cysts in the kidneys. The cysts are filled with fluid. PKD cysts can
slowly replace much of the mass of the kidneys, reducing kidney function and
leading to kidney failure. PKD can cause cysts in the liver and problems in other
organs, such as the heart and blood vessels in the brain. These complications help
doctors distinguish PKD from the usually harmless "simple" cysts that often form in
the kidneys in later years of life. ADULT POLYCYSTIC kidney disease (APKD)
is characterized by large cysts in one or both kidneys and a gradual loss of normal
kidney tissue which can lead to chronic renal failure.