Question

A. Which cells are responsible for blood clotting?

B. Name 3 major steps of blood clotting.

Answer 1

Answer-A- Blood coagulation is initiated by plasma proteins and cell fragments called platelets (thrombocytes). Thromboplastin liberated from platelets is essential for clotting. Clotting of blood is a defence mechanism that protects the body from haemorrhage.

Answer-B- The three important steps in blood coagulation are:

1. Vasoconstriction.
2. Platelet Plug formation
3. Clot Formation

Vasoconstriction:
Also known as vascular spasm, is the first response to the injury.
The vascular constriction is triggered by various factors,
1. The damaged vascular smooth muscle cells release signals to constrict the blood vessels thereby reducing the amount of blood leaked out of the blood vessel.
2.The pain receptors send the signal to the brain, which in turn activates the clotting process.
3.Collagen is exposed at the site of injury, which initiates the activated platelets present in the blood to aggregate leading to the next step.

Platelet Plug Formation:
The platelet sticks together at the site of injury to form a platelet plug, temporarily sealing the leak known as Primary Hemostasis.
Platelets adhere to the collagen fibres in the vessel wall.
Clot Formation (Coagulation):Coagulation is the process clot formation which seals the damaged blood vessels known as Secondary Hemostasis.

Coagulation cascade includes both cellular & protein components.