blood clotting

Question 1

purpose of blood clotting

Answer 1

when an injury occurs that involves damage to blood vessels, the events that follow help to minimise blood loss from broken vesels and prevent entry of infectious micro-organisms

Question 2

1. vasoconstriction

Answer 2

the muscles in the walls of small arteries that have been broken constrict immediately to reduce blood flow and further, blood loss

Question 3

2. platelet plug

Answer 3

internal walls of blood vessels are smooth, until damage creates a rough surface
- platelets stick to the rough surface, and then these stuck platelets attract more
- the platelets build up and form a plug to reduce blood loss
- platelets release substances that act as vasoconstrictors, which enhance and and prolong the constriction of damage vessels

Question 4

3. coagulation

Answer 4

for more serious injuries - coagulation/blood cots
- clotting factors (chemical substances) are present in blood plasma
- a complex series of reactions results in the formation of threads of an insoluble protein called fibrin
- fibrin forms a mesh that traps BC, platelets and plasma
- the mesh with its material is a clot, the threads stick to damaged vessels and hold the clot in position