A good number of chemical reactions take place inside the cells of
an organism. So, all the physiological phenomena are performed neatly.
Organisms remain alive. Some products are produced by chemical reactions which are
essential for body. The products of some of these reactions are poisonous and
these must be removed from the body. For example, the breakdown of glucose
during respiration produces carbon dioxide. This is carried away by the blood
and is removed from lungs. Elimination of nitrogenous waste products and
various diseases in kidney are discussed in this chapter.
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Human Excretion
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Metabolism is the biological process through which waste products
are produced in and excreted from the body. These substances are of no use for
the body, but it may cause various diseases if they remain inside the body for
a long time. It may cause death. Excretory system assists to remove the
poisonous products from the blood that maintains the physiological balance. Excessive
water, salt, carbon dioxide and organic substances are excreted or expelled
from the body.
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Excretory
system
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Kidney is the excretory organ. The basic unit of kidney is
nephron.
Excretory products
Basically excretory product means nitrogenous waste. Human excretory
product is expelled from the body as urine. Almost 90% water is the component
of urine. Other components are urea, uric acid, creatanine and different kinds of
salts. The color of the urine is light yellow due to the presence of a pigment
called urochrome. Excessive intake of proteins increases the acidity, fruits
and vegetables generally make the urine alkaline.
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A
nephron
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Kidney
Excretory organ of human body is kidney. Two kidneys lie at the
back of the abdominal cavity, on either side of the vertebral column and lower
part of the ribcage attached to the back wall. They are red brown and bean
shaped. The outer side of the kidney is convex and inner side is concave having
an indentation called hilus. The chamber in the hilus is pelvis. There are two
uretus (urinary duct) one arising from the pelvis of each kidney and proceeding
downwards to open into the urinary bladder. From the hilus the renal vein comes
out and renal artery enters the kidney. Pelvis is the enlarged funnel shaped
part of the ureter.
Each kidney is enclosed by one type of fibrous membrane. This is
capsule. In longitudinal section of each kidney shows two regions, the outer
one is cortex and part is inner medulla. The regions are composed of connective
tissues and blood vessels. Generally, there are 8-12 renal pyramids in the
medulla. The apex of each pyramid is called papilla.
Each kidney contains a particular type of tubules, these are
uriniferus tubules. Each uriniferus tubule has two parts, such as- nephron and
collecting tubule. Urine is produced in nephron and collecting tubules carry
urine to the pelvis.
Nephron
The functional unit and secretory part of uriniferons tubule of
kidney is nephron. Each human kidney contains about 1 million (1,000,000)
nephrons. Each nephron is composed of a renal corpuscle, malphigian body and
renal tubule.
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A
nephron
|
Each renal corpuscle is divided into two parts, glomerulus and
Bowman’s capsule. Bowman’s capsule encloses the glomerulus. Each Bowman’s
capsule is a cup shaped organ and composed of two epithelial layers. The Bowman’s
capsule, containing a small cluster of blood vessels is called glomerulus.
Afferent arteriole from the renal artery enters the capsule, after entering the
Bowman’s capsule it breaks into about 50 capillaries. These capillaries divide
again and form a mass of fine capillaries. These capillaries unite together and
form efferent arteriole and leave the Bowman’s capsule.
Glomerulus acts as a filter and produces glomerular filtrate from
the blood. The convoluted tubule behind the Bowman’s capsule, which spreads up
to the collecting tubule, is called the renal tubule. Each kidney contains
about 2 million renal tubules. Each renal tubule is divided into three regions
e.g. proximal convoluted tubule,
Henley’s loop and distal convoluted tubule.
A normal adult man expels almost 1500 milliliter urine daily.
Urine contains nitrogenous waste products, such as- urea, uric acid, ammonia, creatanine
etc. These are very much harmful to health. Kidney has an important role to
eliminate these harmful and needless products. Each nephron of the kidney is
continuously producing urine through a complex process. This urine reaches to
the pelvis of the kidney through collecting tubules and proceeds through the
funnel like extended part of the pelvis and enters ureter. Ureter carries urine
from kidney to urinary bladder, stores there for the time being. When the urinary
bladder is filled up with urine, a sensation of urination is created and allows
urine to pass out of the body through urethra. In this way kidney helps to
expel nitrogenous waste product from the body. Kidney maintains the balance of
mineral salts e.g. Sodium chloride, potassium chloride etc. Besides this it
maintains the balance of water, acid and base of blood.
Osmoregulation
For all physiological processes adequate amount of water is
inevitable. Basically, most of the water goes out of the body as urine. The
main function of kidney is to keep balance of water. Nephron of kidney
maintains the water equilibrium by re-absorption. Liquid substances are
filtered in glomerulus. If the blood contains too much water, blood becomes
dilute. It creates different complexity within the body, such as – excessive nitrogenous
products in blood, harm of cell, disturbance in blood transportation etc.
Kidney stone
Small stones like substances produced by kidney are known as
kidney stone. Anyone can be attacked by these diseases. But it has been noticed
that the male have the higher possibility of stone formation than the female. Excessive
body weight/obesity, infection in kidney, drinking insufficient water, in
taking of excessive protein e.g. meat and eggs are the causes of kidney stones.
Initially formation of kidney stones causes no remarkable problem
and problem occurs when it goes downward the ureter water and obstructs
urination. A very dull and steady pain in the back waist is the symptom of this
disease. Blood passes into the urine. Fever starts with shaking. Treatment
depends upon the size and location of the stones. Stones can be removed by
taking sufficient water and medicament. Stones can be removed be the modern
methods uterus stereoscopic conic, ultra sonic lithotripsy or surgical
operation.
Kidney failure
Kidney failure occurs gradually from the diseases like nephritis,
Diabales, hypertension (high blood pressure). Complex nephritis, excessive
blood loss, diarrhea etc. are the causes of sudden kidney failure.
Symptoms of kidney failure are difficulty in urination, increased
level of creatanine in blood. Kidney machine (dialysis machine) can be used to
remove the harmful waste products from a patient’s blood. The patient has to
use the kidney machine after particular / definite intervals and the blood is
purified.
Kidney dialysis
When kidney failure happens then the process of purifying by
scientific method is named dialysis. Usually with the help of kidney machine,
blood can be purified.
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Dialysis
machine
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A kidney machine (dialysis machine) receives blood through a tube
connected to an artery. Inside the machine blood flows through dialysis tubing which
allow small molecules, including urea, uric acid to pass through its walls. The
‘cleaned’ blood is returned to the patient through a tube connected to a vein.
The dialysis tubing is bathed in a liquid similar to blood plasma.
In this way a kidney machine purifies blood through dialysis tubing. This
allows wastes to diffuse out of the blood. But regular dialysis is expensive
and time consuming.
Kidney transplantation
An alternative to this is kidney transplantation. A person can
survive adequately with one kidney. In such cases it is to replace the diseased
kidney with a normal kidney from some other person. But one should be aware /
sure of tissue matching between donor and recipient. There is every possibility
of tissue matching if it is donated by parents, brother or sisters and nearest
relatives. Again the kidney transplant can be done by collecting it from a dead
man. Here dead means “brain death”. Like posthumous eye donation kidney
donation can save the life of a kidney failure patient. Donation of posthumous
kidney is a good service to mankind.
Leading unhealthy living, drinking insufficient water causes
urinary tract or ureter disease. Infection in ureter causes burning sensations
along with other symptoms. Consult with doctor as soon as immediately and with
proper treatment most patients recover completely.
Measure to keep the urinary tract sound / free from diseases
Be careful about the tonsillitis and scabies of the children; keep
control of high blood pressure and diabetes. Immediate treatment for diarrhea,
blood loss, avoid smoking and pain relieving medicine, drink adequate amount of
water, lead a regular life.
End
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