Page 112 - Science Class 07
P. 112
THE PROCESS OF EXCRETION IN HUMAN For example:
BEINGS v If urine test shows that it contains glucose,
You have just studied about the human it is considered that the person may be
exeretory system. suffering from diabetes mellitus.
Let’s see how does it work: v Frequent discharge of urine also indicate
that the man may be suffering from
v The blood of the circulatory system also
diabetes.
passes through the kidneys for the removal
of waste products that it contains. v If urine contains blood it is considered that
man may be suffering from any infec on in
v When this blood passes through the
kidneys, the nephrons present in the excretory system or kidney failure.
kidneys filter this blood and separate waste
products which get collected in tubules of
the nephrons. Our body needs 2-3 litres of water daily to
v The filtrate (free of blood cells and flush out the urea from the body and to
proteins) moves into the tubules. keep the concentra on of sugar at a low
level. It also saves the kidneys from the
v Some of the useful products such as
toxins produced by the body bacteria. If not
glucose and amino acids are also filtered.
checked, blood can pass into the urine and
These useful products are reabsorbed into
it is a clear cut sign of damaged kidneys.
the blood through the walls of the tubules.
v The waste products are sent to urinary DIALYSIS
bladder through ureter for storage. When kidneys are damaged, the excretory
v During storage, the muscle sphincter at the system fails to remove toxic wastes which can
base of the urethra remains contracted. be fatal for the pa ent. Doctors keep such
pa ents on dialysis to remove toxic wastes
Accumula on of urine distends the
through ar ficial methods. Dialysis is an
bladder. A certain degree of muscular
ar ficial filtra on of the blood through semi-
tension s mulates the sense organs in the
permeable membrane to remove urea and
wall of the bladder and the resultant
other wastes. However, there is another way to
contrac on of its muscles expels the urine.
treat such pa ents. This is kidney transplant in
MALFUNCTION OF THE EXCRETORY SYSTEM which the pa ent’s kidney is replaced by
You know, the kidneys are the most important donor’s kidney. You should remember that a
organs of the excretory system and they man can survive with a single kidney.
perform the most important func on, i.e., Procedure of Dialysis
removal of toxic wastes from the body. During dialysis, blood from the arm is allowed
Therefore, any kind of malfunc on of the to flow into the dialysing machine. This is made
kidneys can be dangerous for life. The up of a long cellophane tube coiled in a
malfunc oning of excretory system can be chamber with a dialysing solu on. When the
detected by the examina on of urine blood pass through this machine, the impure
cons tuents. substances are separated and the pure blood is
sent to pa ent’s body.
112 Science-7
