Kidneys... The waste disposal units
Your two kidneys - the renal organs - are the master chemists
of the body. They monitor the quality of the blood, separating out
harmful substances from beneficial ones. They act as waste disposal
units. The kidneys maintain the internal environment essential for life
- whatever the diet or the climate.
The kidneys filter the blood, clean it and keep its composition
balanced. They maintain the correct levels of fluids, minerals and other
substances including salt and water. They react to hormones from the
brain and produce vital hormones of their own.
We can live quite well with only one kidney - indeed, some people
live healthily even though born with only one kidney. But while bones
can break, muscles can atrophy (waste away) and the brain can sleep
without risk to life, if both kidneys fail - renal failure - neither
bone nor muscle nor brain can carry on.
Instead, wastes and fluids will build up and poison our whole system.
This is why people who suffer from renal failure need to have the blood
cleaned artificially with a dialysis machine, or require a kidney
What the kidneys look like...
The kidneys are smooth, maroon, bean-shaped organs, each about the
size of a child's fist and weighing around 140-170 grams (5-6 ounces).
They are located within the abdomen, near the middle of your back,
just above the waistline on each side of the spine. They are buried in
protective fat - below the liver on the right, below the spleen on the
Blood flows into the kidneys through renal arteries, which comes from
the aorta, the main artery of the body leading from the heart. The renal
arteries divide and sub-divide into ever smaller branches, ending in
coils known as glomeruli, which are capillaries (the smallest blood
vessels) that act as filters.
We have about a million of these hairpin-like glomeruli at birth, but
are reduced by a 100,000 with each decade (ten years) of life.
Droplets of filtered blood pass through a number of tubules (tiny
tubes) into the medulla, a central collecting region. The glomeruli and
tubules together make up nephrons, long and extremely fine tubes which,
if connected, would run for 80 kilometres (50 miles).
The nephrons are the basic working units of the kidneys, controlling
the formation of urine. Extending from each kidney is a vein through
which filtered blood flows back into the circulation. There is also a
duct from each kidney called the ureter, which carries urine to the
How to keep your kidneys healthy
* As with all aspects of keeping fit, the basic rule is to be kind to
your body - maintain a sensible, balanced diet and do not smoke, take
drugs or drink alcohol.
* Drink one and a half to two litres of water a day and drink only
moderate amounts of tea, coffee and cola because they contain caffeine.
This, like alcohol, is a diuretic - which means that it dehydrates the
* Stick to a diet high in carbohydrates and low in protein (the main
source of waste products) as this reduces the kidneys' workload.
* Like the rest of our amazing body, the kidneys are designed to last
a lifetime. They do a wonderful job of maintaining our internal
environment and should continue to do so, as long as we look after them
by drinking plenty of water and eating a balanced healthy diet.
What the kidneys do
The kidneys keep the blood clean by filtering it to clear it of
wastes, such as creatinine, left over from the breakdown of muscle, and
urea, from the breakdown of proteins. The filtered wastes are combined
with water to make urine, which passes down into the bladder.
The kidneys keep the blood in chemical balance (homeostasis),
maintaining fluids, minerals (such as calcium and magnesium) and
electrolytes (such as sodium and potassium) at the right levels. About
400 gallons (1,800 litres) of blood are pumped through the kidneys every
The kidneys also regulate water, which accounts for more than half
the body's weight. If too much water is lost, as through sweating, the
kidneys respond to try to conserve it.
The kidneys react to hormones from the brain. They also produce three
important hormones of their own: 1. Erythropoietin (EPO), which
stimulates the bone marrow to make red blood cells 2. Renin, which helps
to regulate blood pressure 3. The hormonal form of Vitamin D, which
helps maintain calcium for bones and for chemical balance
What can go wrong with the kidneys?
There are often no symptoms in the early stages of many kidney
conditions. When they do occur, the initial signs may be general -
frequent headaches or feeling tired or generalised itching. As kidney
disease progresses, the symptoms can include changes in the urine
(reduced volume, discolouration, blood or pus), nausea and vomiting and
Other symptoms include swollen or numb hands and feet (because of
water retention), weakness and lethargy, darkened skin and muscle