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ORGANS OF THE HUMAN URINARY SYSTEM
1. The principal systemof excretion is the
urinary system, which
is considered far more
efficient than themost modern sewage
disposal system in the
world. The urinary
system, consisting of
the kidneys, ureter,
urinary bladder, and
urethra, disposes
such metabolic
nitrogenous wastes as
urea, uric acid, and
creatinine.
2. Organs of the Urinary Systema. The kidneys are two bean-shaped
organs, each about four inches long and lying near
the base of the spinal cord. Each contains about half
a million tubules called nephrons, which are the filter
devices of the kidneys. The function of the kidneys is
primarily to eliminate nitrogenous wastes, excess
water, sugar, mineral salts, and other toxic or
unnecessary substances. As blood passes through
the glomerulus, a ball of capillaries on top of the
nephrons, the wastes are collected by the tubules
and sent for temporary storage to the urinary
bladder through the ureter.
b. The ureter is the long tube that leads from the kidneys to the urinary bladder.c. The urinary bladder is the bag that temporarily holds the urine.d. The urethra is the tube exit for the urine.
3. Blood and urine are two body fluids associated with kidneys. Each of these fluids can provideinformation about the health condition of the body.
4. A urine analysis is often performed in order to determine the state of a patients health. Thisanalysis consists of tests that can detect various substances in the urine that can provide clues
to various disorders and ailments. These tests are as follows:
a. Acidity Test. Normal urine is slightly acidic.b. Protein Test. The presence of protein may indicate kidney infection.c. Blood Test. The presence of blood may indicate chemical poisoning or internal bleeding.d. Glucose Test. The presence of sugar may indicate diabetes or kidney infection.
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COMMON AILMENTS OF THE URINARY SYSTEM
1. The urinary tract may sometimes get infected by microorganisms, which usually enter the bodythrough the urethra, other body organs, or the blood. Some infections can be treated by
drinking lot water, resting, cushioning your diet, or taking antibiotics. Other infections are
more serious and need medical attention.
2. Nephritis. When the nephrons of the kidneys become infected, a disease called nephritis mayresult. The disease causes inflammation of some parts of the kidney, reducing its ability to
filter blood. if untreated or if it occurs repeatedly, the infection can damage the kidneys to the
point that they cannot remove wastes anymore. The body becomes poisoned with its own
waste, resulting in a condition called uremia.
3. A person with severe kidney damage may have to be connected to an artificial kidney, called adialysis machine. During dialysis, the patients blood is pumped into special tubing made ofsemipermeable membrane and surrounded by a special fluid. Wastes and other unneeded
materials diffuse from the tubing into the fluid. At the same time, certain substances from the
fluid diffuse into the blood. in this way, the blood is cleansed and replenished. The blood then
flows back into the person.
4. If the kidneys no longer function, a new kidney may have to be transplanted. Fortunately, onekidney is enough to do the work of two.
5. Kidney Stones. Thesestones form in the
kidneys when salts in
the urine form
crystals. The stones
may be as small as
gravel or large enough
to block the ureter
and keep urine from
leaving the kidneys.This can be a very
painful experience. If
the stone is not
removed, it can lead
to the destruction of
the kidneys.
6. Kidney stones areoften treated with atechnique called
ultrasound. The ultrasonic vibrations break up the stones into smaller pieces so they can pass
out of the ureter.
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THE SKIN
1. The skin is the largest organ of the human body, weighing up to 4.5 kg, with a surface area ofabout 17,000 sq.cm. in the average adult. It is divided into three tissue layers: epidermis (outer
layer), dermis (inner layer), and the subcutaneous layer.
2. Structures ofthe Skin
a. TheEpidermis. The
epidermis is
subdivided into 4
layers. The top layer
is made up of dead
cells containing
keratin, which
toughens the skin.
The bottom layer is
made up of live,
reproducing cells
whose main purpose
is to replenish the top
layer. These cells move up through the two intermediate layers until they arrive, dead at
the surface. The bottom layer also contains cells producing a brown pigment called
melanin, the bodys adaptation against ultraviolet radiation. The greater the melanin, the
darker is the skin. Exposure to sunlight and artificial ultraviolet tends to increase the
melanin production.
b. The Dermis. The dermis contains nerve endings, blood vessels, fatty tissue, and glands. Thedermis has tiny projections called papillae, which help join the dermis to the epidermis.
c. Under the dermis is a flexible tissue containing many spaces called areolar tissue whichconnects the skin to the body and helps the skin intact.
3. The skin has two kinds of glands:a. Sebaceous glands. Sebaceous glands secrete oil called sebum, which lubricate the hairs and
surface.
b. The Sweat Glands. The sweat glands are of two kinds: eccrine and apocrine. The eccrineglands secrete sweat that cools the body. The apocrine glands secrete a small amount of
fluids that give odor to the skin.
4. The skin can be considered another organ of excretion of the human body for excess water,urea, and mineral salts. The sweat gland is the principal excretory structure of the skin. It
consists of a long tubule which is partly coiled at the lower end. The upper end is straight andleads to an opening on the skin called pore.
5. The excretion of the fluid waste through the pores of the skin is called perspiration. The fluidwaste is also called sweat.