The document discusses the role of platelets in hemostasis, detailing their structure, which includes glycoproteins and two types of granules. It outlines the functions of platelets, such as adhesion, activation, aggregation, and procoagulant activity, leading to the formation of a platelet plug. Ultimately, it describes how the activation of platelets causes firm clot formation and promotes blood circulation.

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. Procoaggulant activity

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)