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KIDNEY ANATOMY |
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OVERVIEW |
 Kidneys are fist-sized organs located near the middle
of the back, just above your waist. Their job is to
filter and get rid of waste from the body, and make
chemicals
(hormones) that keep the bones strong and the blood
healthy. Most
people have two kidneys to help deal with water and
waste. As blood passes
through the kidneys, it is "cleaned": that is, the
body’s waste products and
excess fluid are removed from the blood. These waste products, along
with any excess fluid, are then sent through the ureters to the
 . They
are then passed out of the body as urine.
Kidney functions:
Removing
toxins.
The kidneys are responsible for removing wastes and
toxins from the bloodstream, producing urine in the
process.
Regulating
water within the body.
Kidneys make sure the body contains the amount of
water it needs to work properly, removing excess water
or retaining water as necessary.
Regulating
hormones.
Kidneys release three different hormones that help
regulate blood pressure, produce red blood cells and
provide calcium for strong bones.
Controlling chemicals.
Kidneys monitor the amount of sodium, phosphorus and
potassium in the blood, and make sure there is the
right balance of these substances.
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| Maintaining the body’s water
balance |
| By removing excess fluid from your body. |
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| Removing waste products
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| There
are many chemical reactions that take place in your
body to keep you |
alive.
This process is called
 .
Metabolism results in waste products |
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become poisonous if they are left to build up in your
body. Healthy kidneys |
filter blood
to get rid of waste products such as
 and
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| Maintaining normal blood
chemistry
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Lots of chemicals such as
 ,
 ,
 ,
 ,
, |
 ,
and
are important to your blood chemistry. |
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Healthy kidneys make sure you keep the right amounts
of these chemicals and |
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rid of those you don't
need. |
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| The
kidneys also produce chemical messengers called
hormones. The three |
important hormones the kidney makes are-
 ,
and
 . |
| These hormones help you with many body functions: |
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Renin: keeps your blood pressure steady
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Erythropoietin: makes sure that you have enough red blood
cells so that you |
don’t
become
 . |
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Calcitriol: absorbs enough calcium from the food that you
eat to keep your |
| bones
strong and healthy. |
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| People
can live a relatively normal life with only one
working kidney. However, if both
kidneys stop working properly, a number of symptoms
can develop and a
replacement will be necessary. |
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In situations where both
kidneys have stopped working,
 is
required. An
organ transplant may be the best option for those who
are suitable as it offer the best
replacement of kidney function. |
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Kidney
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Short descriptions
of the parts of the kidney labelled above:
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Renal hilus: |
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The renal hilus
is an indentation near to the centre of the
concave area of the kidney. This is the area of
the kidney through which the ureter leaves the
kidney and the other structures including blood
vessels (illustrated), lymphatic vessels, and
nerves enter/leave the kidney. |
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Renal capsule: |
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The renal capsule is a
smooth, transparent, fibrous membrane that
surrounds, encloses, and protects the kidney. Each
kidney has it's own renal capsule (outer layer),
which helps to maintain the shape of the kidney as
well as protecting it from damage.
The renal capsule is itself surrounded by a mass
of fatty tissue that also helps to protect the
kidney by damage by cushioning it in cases of
impact or sudden movement. |
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Renal cortex: |
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The renal cortex is the
outer part of the kidney and has a reddish colour
(shown as very pale brown above). It has a smooth
texture and is the location of the Bowman's
Capsules and the glomeruli, in addition to the
proximal and distal convoluted tubules and their
associated blood supplies (these
structures are part of the kidney nephrons -
described in further detail on the page about
kidney nephrons). |
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Renal medulla: |
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The renal medulla is the
inner part of the kidney. "Medulla" means "inner
portion". This area is a striated (striped)
red-brown colour. |
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Renal pyramids: |
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There are approx. 5 - 18
striated triangular structures called "Renal
Pyramids" within the renal medulla of each kidney.
The apperance of striations is due to many
straight tubules and blood vessels within the
renal pyramids. |
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Renal pelvis: |
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The renal pelvis is the
funnel-shaped basin (cavity) that receives the
urine drained from the kidney nephrons via the
collecting ducts and then the (larger) papillary
ducts.. |
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Renal
artery: |
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The renal vein delivers
oxygenated blood to the kidney. This main artery
divides into many smaller branches as it enters
the kidney via the renal hilus. These smaller
arteries divide into vessels such as the segmental
artery, the interlobar artery, the arcuate artery
and the interlobular artery. These eventually
seperate into afferent arterioles, one of which
serves each nephron in the kidney. |
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Renal vein: |
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The renal artery receives
deoxygenated blood from the peritubular veins
within the kidney. These merge into the
interlobular, arcuate, interlobar and segmental
veins, which, in turn, deliver deoxygenated blood
to the renal vein, through which it is returned to
the systemic blood circulation system. |
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Interlobular artery: |
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The interlobular artery
delivers oxygenated blood at high pressure to the
glomerular capillaries. |
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Interlobular
vein: |
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The interlobular vein
receives deoxygenated blood (at lower pressure)
that it drains away from the glomerular
filteration units and from the Loops of Henle.
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Kidney nephron: |
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Kidney nephrons are the
functional units of the kidneys. That this, it is
the kidney nephrons that actually perform the
kidney's main functions. There are approx. a
million nephrons within each kidney. To find out
more about these, visit the page about Kidney
Nephrons. |
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Collecting Duct
(Kidney): |
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The collecting duct
labelled in the diagram above is part of the
kidney nephron (shown much enlarged). The distal
convoluted tubules* (term
explain on the page about kidney nephrons)
of many nephrons empty into a single collecting
duct. Many such collecting ducts unite to drain
urine extracted by the kidney into papillary
ducts, then into a minor calyx, then the major
calyx (at the centre of the kidney), and finally
into the ureter through which the urine leaves the
kidney en-route to the urinary bladder. |
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Ureter: |
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The ureter is the structure
through which urine is conveyed from the kidney to
the urinary bladder.. |
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Causes of Kidney Failure |
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The most common causes of kidney failure are
 ,
 , |
and
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Most kidney diseases
attack the nephrons, causing them to lose their
filtering capacity. Damage to the nephrons may happen
quickly, often as the result of injury or poisoning.
But most kidney diseases destroy the nephrons slowly
and silently. Only after years or even decades will
the damage become apparent. Most kidney diseases
attack both kidneys simultaneously.
The two most common causes
of kidney disease are diabetes and high blood
pressure. If your family has a history of any kind of
kidney problems, you may be at risk for kidney
disease.
Diabetic Nephropathy
Diabetes is a disease
that keeps the body from using glucose (sugar) as it
should. If glucose stays in your blood instead of
breaking down, it can act like a poison. Damage to the
nephrons from unused glucose in the blood is called
diabetic nephropathy. If you keep your blood glucose
levels down, you can delay or prevent diabetic
nephropathy.
High Blood Pressure
High blood pressure can
damage the small blood vessels in your kidneys. The
damaged vessels cannot filter wastes from your blood
as they are supposed to.
Your doctor may
prescribe blood pressure medication. Blood pressure
medicines called angiotensin-converting enzyme (ACE)
inhibitors and angiotensin receptor blockers (ARBs)
have been found to protect the kidneys even more than
other medicines that lower blood pressure to similar
levels. The National Heart, Lung, and Blood Institute
(NHLBI), one of the National Institutes of Health,
recommends that people with diabetes or reduced kidney
function should keep their blood pressure below 130/80
mm Hg.
Glomerular Diseases
Several different types
of kidney disease are grouped together under this
category, including autoimmune diseases,
infection-related diseases, and sclerotic diseases. As
the name indicates, glomerular diseases attack the
tiny blood vessels (glomeruli) within the kidney. The
most common primary glomerular diseases include
membranous nephropathy, IgA nephropathy, and focal
segmental glomerulosclerosis. Protein, blood, or both
in the urine are often the first signs of these
diseases. They can slowly destroy kidney function.
Blood pressure control is important with any kidney
disease. Treatments for glomerular diseases may
include immunosuppressive drugs or steroids to reduce
inflammation and proteinuria, depending on the
specific disease.
Inherited and Congenital Kidney
Diseases
Some kidney diseases
result from hereditary factors. Polycystic kidney
disease (PKD), for example, is a genetic disorder in
which many cysts grow in the kidneys. PKD cysts can
slowly replace much of the mass of the kidneys,
reducing kidney function and leading to kidney
failure.
Some kidney problems
may show up when a child is still developing in the
womb. Examples include autosomal recessive PKD, a rare
form of PKD, and other developmental problems that
interfere with the normal formation of the nephrons.
The signs of kidney disease in children vary. A child
may grow unusually slowly, may vomit often, or may
have back or side pain. Some kidney diseases may be
“silent” for months or even years.
If your child has a
kidney disease, your child’s doctor should find it
during a regular checkup. Be sure your child sees a
doctor regularly. The first sign of a kidney problem
may be high blood pressure, a low number of red blood
cells (anemia), or blood or protein in the child’s
urine. If the doctor finds any of these problems,
further tests may be necessary, including additional
blood and urine tests or radiology studies. In some
cases, the doctor may need to perform a
biopsy—removing a tiny piece of the kidney to examine
under a microscope.
Some hereditary kidney
diseases may not be detected until adulthood. The most
common form of PKD was once called "adult PKD" because
the symptoms of high blood pressure and renal failure
usually do not occur until patients are in their
twenties or thirties. But with advances in diagnostic
imaging technology, doctors have found cysts in
children and adolescents before any symptoms appear.
Other Causes of Kidney Disease
Poisons and trauma, for
example a direct and forceful blow to your kidneys,
can lead to kidney disease.
Some over-the-counter
medicines can be poisonous to your kidneys if taken
regularly over a long period of time. Products that
combine aspirin, acetaminophen, and other medicines
such as ibuprofen have been found to be the most
dangerous to the kidneys. If you take painkillers
regularly, check with your doctor to make sure you are
not putting your kidneys at risk. |
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How the kidneys work
Waste materials in the blood
come from the normal breakdown of active tissues and the food that
you eat. After your body has taken what it needs for energy and to
repair itself, the waste is carried in the blood and passed
through the filtration system of the kidney.
Every minute, your kidneys
process about 1.3 litres of blood to sift out the waste
products and extra water. If your kidneys did not
remove these wastes, they would
build up in the blood and damage your body.
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| The
actual processing or filtering of the blood occurs in
small units inside your |
kidneys called
 .
Every kidney has about a million nephrons in total. |
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In the nephron, a structure
called the
acts as the main filter for |
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the blood. It is actually a very small blood vessel,
or capillary, that is |
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wrapped around a very small urine-collecting tube
called a tubule. |
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| A
complicated chemical exchange takes place, as waste
materials and water |
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your blood and enter your urinary system. |
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| During the process of
filtration, your kidneys measure the levels of chemicals like |
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,
,
and
and decide how much of each is |
| needed
to be released back into the blood so it can return to
the body. |
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this way, your kidneys regulate the body's level of
these substances. |
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right balance of the chemicals is necessary for life,
as levels that are |
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high or too low can be harmful. |
