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Science
Notes For Class 7th
Chapter-11
Transportation in Plants and Animals
All organisms need
food, water and oxygen for survival. Further, animals need to transport waste
to parts from where they can be removed.
Circulatory
System.
Blood- Blood is a fluid that flows in blood vessels. It
transports substances like digested food from the small intestine to other
parts of the body.
It
carries oxygen from the lungs to the cells of the body. It also transports
waste for removal body.
Blood
is composed of a fluid, called plasma in
which different types of cells are suspended.
One type of
cells are the Red blood cells(Rbc) that contain Red pigment called Haemoglobin. Haemoglobin binds with oxygen and
transports it to all parts of the body and ultimately to all cells.
The white
blood also has white blood cells (Wbc)
which fight against germs that may our body.
If you fell down while playing
a game and your knee got injured. So you have realised after some time, you
noticed that bleeding had stopped and a dark red clot had plugged the cut.
This clot is formed because of the presence of another type of cells in the blood,
called platelets.
So,
two types of blood vessels. arteries and veins are present in the
body.
Arteries
carry oxygen-rich
blood from the heart to all the parts of the body.
Can
you feel some throbbing is called the pulse and it is due to the blood flowing in the arteries. The number of beats per minutes is called the pulse rate. The arresting person usually has a pulse rate between
72 and 80 bets per minutes.
Veins
are
the vessels which carry carbon dioxide-rich blood from all parts of the body back
to heart. The veins have thin walls. There are valves present in veins which
allow blood to flow only towards the heart.