6.platelet hemostasis hematology lectures. ppt

Hematology lectures

1. Amani Awad Ashmaig

2. Platelets in haemostasis
It cytoplasmic fractures of megakaryocyte formed from
:
Bilayer membrane consist of several glycoproteins: GP
1a , 1b , 11b , 111a
Granules : alpha and dense granules.

3. Alpha granules contain:
Platelet drive growth factor (PDGF): thrombopoisis
Platelet factor 4 (PF4): neutralize heparin
Fibrinogen : clotting factor
Fibronectin
Factor V: clotting factor
VWF

4. Dense granules contain:
ADP : platelet agonist
ATP : platelet agonist
Serotonin : platelet agonist
Calcium :clotting factor

5. Function of platelets in haemostasis:
1.Adhesion
2.Release reaction
3.Aggregation
4.Infusion function
5.Procoaggulantactivity

6. Formation of platelet plug:
Adhesion through glycoprotein receptor in blood
vessel
Spreading adhesion
Platelets activated by change their shape from discoid
to sphere with pseudopodia to contact with each other

7. Granules move from the center to the peripheral in the
pseudopodia and release their content.
As result of release reaction platelets agonist will call
other platelets from circulation and activate them.
Activated platelets will align to each other causing
platelet aggregation

8. Platelets produce thrombotherin that cause retraction
and release the entrapped serum to give firm clot and
open blood vessel for circulation ( infusion function).
At last platelets cause activation of several clotting
factor ( procoaggulant activity)