young adult it will be 120 mm of Hg. The second reading is taken during
the resting period, as the ventricles refill with blood. This is called diastolic
pressure. It will be 80 mm of Hg.
B.P. will change according to the activity in which the person is
engaged, such as resting, walking and running. People who have high B.P.
during resting period are said to have hypertension. Discuss with your
teacher about low blood pressure.
Coagulation of blood
Another important part in the story of blood is coagulation. Only
because of this character animals survive when they meet severe injuries.
When there is an injury blood clots in 3-6 minutes. How does the
blood clot? What chemistry involved in blood coagulation. You know that
when you cut yourself, the blood flows out of the wound for only a short
time. Then the cut is filled with a reddish solid material. This solid is
called a blood clot. If blood did not clot, anyone with even a slight wound
bleeds profusely.
When the blood flows out, the platelets release an enzyme called
thrombokinase.
Thrombokinase acts on another substance present in the blood called
pro-thrombin converting it into thrombin.
Thrombin acts on another substance called fibrinogen, that is present
in dissolved state converting it into insoluble fibrin.
The blood cells entangle in the fibrin fibres forming the clot.
The fibrin fibres are attached to the edges of the wound and pull them
together.
The yellowish straw coloured fluid portion after formation of the clot
is serum.
Discuss with your teacher about vitamin K in relation to coagulation of blood.
