Page 104 - Science Class 07

BLOOD TRANSFUSION There are two types of blood circula on in our
Blood is formed in our body by a natural
process. Though scien sts are trying to find any
suitable subs tute of blood yet they have not
got any success. Therefore, blood is very much
important for our survival. Some mes, in
accidents people get serious injuries and lose a
large amount of blood from their body. It may
be fatal. In some cases of diseases like
anaemia, people become the vic m of
deficiency of blood. A blood loss of 40 percent
of more may be fatal for anyone.
In case of heavy blood loss, the pa ent is
provided with the blood from a healthy person.
The blood is transferred through the veins of
the pa ent. This process is called transfusion
of blood.
The person who is provided with blood is called
the recipient and who gives blood is called the
donor. But you should remember that different
persons have different blood groups such as A,
B, AB and O. In case of blood transfusion, the
recipient and the donor must be of the same
blood group. If the blood group of donor does
not match properly with that of the recipient,
the red blood cells can s ck together and may
cause death of the recipient.
BLOOD CIRCULATION
A great English physician, William Harvey
(1578-1657) first discovered
that blood circulates in
body through blood vessels.
But, his discovery was not
accepted by majority of
doctors. But, a few years
later a er his death it was
proved that blood circulate
in our body through blood
vessels.
Circula on of Blood
104
body:
v Pulmonary Circula on of Blood
v Systemic Circula on of Blood
Pulmonary Circula on of Blood
Deoxygenated blood is collected from different
parts of the body by veins and this blood is sent
to right auricle. This is then transferred to the
right ventricle and is pumped into the right
pulmonary artery which carries it into the
lungs. In lungs, the blood is oxygenated and is
carried by the pulmonary vein to the le
auricle.
Systemic Circula on of Blood
The oxygenated blood from the le auricle
passes to the le ventricle and is then pumped
to all parts of the body to supply oxygen and
the other materials. This process goes on and
on and our body gets required amount of
oxygen.
PULSE RATE AND HEART BEAT
Your pulse is your heart rate or the number of
mes your heart beats in one minute. Pulse
rates vary from person-to-person. Your pulse is
lower when you are at rest and increases when
you exercise (more oxygen-rich blood is needed
by the body when you exercise). Knowing how
to take your pulse can help you evaluate your
exercise program. It can be felt by placing the
index finger on our right hand of the inner side
of or le wrist. Actually, when blood passes
through the arteries with great force from the
auricles to the ventricles the arteries expands.
But, arteries contract when blood flows from
the ventricles to the arteries. Normally, heart
beats 72 mes in a minute. But the heart of a
newly born baby beats 130-140 mes in a
minute. A child’s heart normally beats 90-100
mes a minute.
Science-7