Question

We know that in our blood platelets are present which clots the blood outside the body, then why does they don't clot the blood inside our body?

Answer 1

Answer:

When blood is exposed to new surface or air it clots.

Explanation:

Blood clotting factors are intrinsic and extrinsic. Intrinsic factors when are in cells, tissues and plasma blood do not clot. Some of the factors as surface activation factor stimulates blood to clot when exposed.
Inside the body, the liver secretes a substance called heparin. This prevents clotting of blood in blood vessels. But if there is internal injury, platelets break to release a thermoplastic substance. It initiates clotting.