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What do kidneys do? What do the kidneys do? • The kidneys are bean-shaped organs, each about the size of a fist. They are located near the middle of the back, just below the rib cage, one on each side of the spine. The kidneys are sophisticated reprocessing machines. Every day, a person’s kidneys process about 200 quarts of blood to sift out about 2 quarts of waste products and extra water. The wastes and extra water become urine, which flows to the bladder through tubes called ureters. The bladder stores urine until releasing it through urination. • Wastes in the blood come from the normal breakdown of active tissues, such as muscles, and from food. The body uses food for energy and self-repairs. After the body has taken what it needs from food, wastes are sent to the blood. If the kidneys did not remove them, these wastes would build up in the blood and damage the body.
What is a nephron • The actual removal of wastes occurs in tiny units inside the kidneys called nephrons. Each kidney has about a million nephrons. In the nephron, a glomerulus—which is a tiny blood vessel, or capillary—intertwines with a tiny urine-collecting tube called a tubule. The glomerulus acts as a filtering unit, or sieve, and keeps normal proteins and cells in the bloodstream, allowing extra fluid and wastes to pass through. A complicated chemical exchange takes place, as waste materials and water leave the blood and enter the urinary system.
ureters • Two ureters - narrow tubes that 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 • bladder - a triangle-shaped, hollow organ 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. • two sphincter muscles - circular muscles that help keep urine from leaking by closing tightly like a rubber band around the opening of the bladder. • nerves in the bladder - alert a person when it is time to urinate, or empty the bladder.
urethera • the tube that 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.
FYI 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.
Nephron structure • Kidney nephrons are the functional units of the kidneys. There are typically over 10,000 kidney nephrons in each of the two kidneys in the body.
renal cortex • The cortex is the outer part of the kidney. This is where blood is filtered. We call this process "ultra-filtration" or "high pressure filtration" because it only works if the blood entering the kidney in the renal artery is at high pressure. • Billions of glomeruli are found in the cortex. A glomerulus is a tiny ball of capillaries. Each glomerulus is surrounded by a "Bowman's Capsule". Glomeruli leak. Things like red blood cells, white blood cells, platelets and fibrinogen stay in the blood vessels. Most of the plasma leaks out into the Bowman's capsules. This is about 160 litres of liquid every 24 hours.
renal medulla • The medulla is the inside part of the kidney. This is where the amount of salt and water in your urine is controlled. It consists of billions of loops of Henlé. These work very hard pumping sodium ions. ADH makes the loops work harder to pump more sodium ions. The result of this is that very concentrated urine is produced. • The opposite of an anti-diuretic is a "diuretic". Alcohol and tea are diuretics.
glomerus • the glomerulus filters proteins and cells from the blood.
collecting ducts Collecting ducts run through the medulla and are surrounded by loops of Henlé. The liquid in the collecting ducts (ultra-filtrate) is turned into urine as water and salts are removed from it. Although our kidneys make about 160 litres of urine every 24 hours, we only produce about ½ litre of urine. It is called a collecting duct because it collects the liquid produced by lots of nephrons.
Bowman capsule A cup-shaped structure around the glomerulus of each nephron of the vertebrate kidney. It serves as a filter to remove organic wastes, excess inorganic salts, and water. Bowman's capsule is named after its identifier, English physician and physiologist, Sir William Bowman (1816-1892).
azoturia • Genetic disorder which occurs in both humans and horses, where it is also known as Impressive Syndrome. It is an inherited autosomal dominant disorder which affects sodium channels in muscle cells and the ability to regulate potassium levels in the blood. It is characterized by muscle hyperexcitability or weakness which, exacerbated by potassium or cold, can lead to uncontrolled shaking followed by paralysis.
diuresis • Diuresis is an increase in the production of urine by the kidneys
dysuria • refers to painfulurination • This is typically described to be a burning or stinging sensation. It is most often a result of a urinary tract infection. It may also be due to an STD, bladder stones, bladder tumours, and virtually any condition of the prostate.
end stage renal disease (ESRD) • End-stage kidney disease is the complete, or almost complete failure of the kidneys to function. The kidneys can no longer remove wastes, concentrate urine, and regulate many other important body functions.
enuresis • Refers to an inability to control urination.Use of the term is usually limited to describing individuals old enough to be expected to exercise such control. • Nocturnal enuresis, commonly called bedwetting, is a medical term for involuntary urination while asleep after the age at which bladder control usually occurs
hypospadias • Hypospadias is a birth defect of the urethra in the male that involves an abnormally placed urinary meatus (opening). Instead of opening at the tip of the glans of the penis, a hypospadic urethra opens anywhere along a line (the urethral groove) running from the tip along the underside (ventral aspect) of the shaft to the junction of the penis and scrotum or perineum
interstitial nephritis • is a form of nephritis affecting the interstitium of the kidneys surrounding the tubules. This disease can be either acute, meaning it occurs suddenly, or chronic, meaning it is ongoing and eventually ends in kidney failure.
renal hypertension • High blood pressure that results from kidney disease.
uremia • In kidney failure, urea, nitrogenous waste products , and other waste products, which are normally excreted into the urine, are retained in the blood.
Wilms tumor • cancer of the kidneys that typically occurs in children, rarely in adults
blood urea nitrogen (BUN) test is a measure of the amount of nitrogen in the blood in the form of urea, and a measurement of renal function. Urea is a substance secreted by the liver, and removed from the blood by the kidneys.
kidney, ureter, bladder (KUB) • A KUB is a plain frontal supine radiograph of the abdomen
