this is abt the blood

1. BLOOD {THE CIRCULATING
FLUID IN OUR BODY}
BY SWATI

2. HUMAN CIRCULATORY SYSTEM
The to and fro movement of the blood carried
out by the heart is called the blood circulatory
system.
Our circulatory system consists of heart , blood
and blood vessels.

3. Blood
the blood consists of two parts:-
1. plasma-it is a yellowish fluid which has 90%
water and 10%nutrients such as food ,
vitamins and minerals.
2. corpuscles-is the cellular part

4. Corpuscles of the blood
1. Red blood cells{rbc}-the red blood cells are
circular or disc-shaped. These cells have
nucleus to start with but then they lose it
during maturation. The rbc’s are about 4.5 to
5.0 million in one cubic millimeter of blood.
They are produced in the bone marrow. There
red colour is due to the iron and protein
compound known as hemoglobin which acts
as the “oxygen carrier”.

5. White blood ells {wbc}
The white blood cells are also known as
leuclocytes. They are larger than the rbc’s and
have a distinct nucleus. They are much less in
number ,about 5000-8000 per cubic
millimeter of blood. The wbc’s capture and
destroy germs thus providing immunity.
The wbc’s are of two types:-
1. Granulocytes
2. agranulocytes

6. platelets
• They are somewhat round in shape and
smallest in size. They are about 2-3 lacs per
cubic millimeter of blood. The platelets help in
the clotting of blood thus stopping excessive
bleeding of blood.

7. functions of blood
1. The blood transports the digested food from
the intestines to other organs where they are
either stored or utilised.
2. it carries out cellular wastes to the kidneys
where it is removed out of our body.
3. it protects against diseases by destroying the
germs.
4. it prevents excessive bleeding of blood by
blood clotting.

8. Difference between arteries and veins
Arteries- carry blood away from the heart
- have thick muscular walls
-the blood flows with jerk and under great
force
- usually , deeply placed
Veins-carry blood into the heart
-have thin and less muscular walls
-the blood flows smoothly and under
pressure
- usually placed more superficially.

9. Blood circulation
• the blood returning from the geart is received
in the right auricle
• the oxygen rich blood returning from the
lungs is received in the left auricle
• when the auricles contract they force the
blood into the 2 ventricles.