Understanding Platelets: How They Help Stop Bleeding

Understanding Platelets: How They Help Stop Bleeding

Platelets (or) Functions of platelets.
Answer:

Platelets  are smallest, colourless, non-nucleated, spherical, oval or rounded granulated bodies.

platelets Size:

• 2.5 m in diameter.
• 7.5 cubic microns in volume.

platelets Structure:

• It is non-nucleated
• Cell membrane contains lipids, carbohydrates, proteins and glycoproteins.
• Microtubules form a ring around its cytoplasm.
• The cytoplasm includes golgi apparatus, endoplasmic reticulum, mitochondria, microtubule, microfilaments and granules.
• Cell membrane contains various receptors for combining with specific substances like collagen, fibrinogen and von-Willebrand’s factor.

platelets Normal count:

• 2,50,000/cu mm of blood (2,00,000 to 4,00,000).

platelets Life-span:

• 8-12 days after which it is destroyed is spleen.

platelets Properties: 3A’s

1. Adhesiveness:

• When a blood vessel is injured, platelets adhere to the exposed collagen present on the endothelium cell of the vessel wall.

2. Aggregration:

• It means grouping of platelets.
• The activated platelets become stick to each other.
• This stickiness is due to ADP and thromboxane A2.

3. Agglutination:

• It is the clumping of platelets.
• This property is due to platelet agglutinin and platelet activating factor.

Platelets Functions:

1. Role in hemostasis:

• Platelets prevents blood loss by.
  1. Secreting 5 HT- this causes the vasoconstriction.
  2. Platelets adhesiveness seal the damage blood vessels by forming temporary plugs.
  3. Platelets gets bind to the exposed collagen present on the endothelium of injured blood vessel.

2. Role in blood clotting:

• Platelet play a role in the formation of prothrombin activator of intrinsic pathway of blood coagulation.

3. Role in clot retraction:

• Within 5-30 min of fibrin clot formation, clot retracts to 40% of its original due to contractile proteins like actin, myosin, thrombosthenin in platelets.

4. Role in repair of rupture blood vessel:

• The cytoplasm of platelets contains platelet growth factor which helps in repair of blood vessel.

5. Role in defense mechanism:

• Platelets undergoes phagocytosis of carbon particles, viruses and immune complexes.

6. Storage and transport:

• Platelets stores 5-HT and histamine and release them when needed.