Blood 7 Flashcards
What are the two main types of Granules found in Platelets?
Alpha granules and dense granules
What do Alpha Granules generally contain?
Large molecules: •Adhesion molecules •Some clotting factors •Growth factors •Cytokines
What do Dense Granules of Platelets usually contain?
Small molecules:
•ADP and ATP
•5-hydroxytryptamine (5HT or serotonin)
•Ca2+
What is the abbreviation for Adhesion molecules?
vWF
What do Adhesion molecules do?
Allow things to stick together
What is involved in the formation of a Platelet plug?
- Adhesion
- Activation
- Aggregation
What occurs in Adhesion of platelets?
They stick to the damaged vessel wall
What occurs in Activation of platelets?
They change shape, express various receptors, and secrete various substances
What occurs in the aggregation of platelets?
They stick to each other and form a plug
Where does Platelet plug formation take place?
On the Lumen inside the blood vessels, where the blood is flowing
What is the wall of the blood vessel closest to the blood made out of?
Endothelial cells
What forms the inner lining of the blood vessels?
Endothelial cells
What layer surrounds the endothelial cells of the blood vessels?
Subendothelium
What does the Subendothelium contain?
Many structures, many molecules of connective tissue including collagen
Where in the blood vessels is Collagen found?
In the subendothelial layer
What is above the Subendothelial layer?
Layers of smooth muscle
What initiates the formation of a Platelet plug?
The exposure of collagen in the subendothelial layer of a blood vessel
What occurs after collagen is exposed to the blood when a blood vessel is damaged?
Platelets stick to the collagen through an intermediary molecule called Von Willebrand (vWF)
How do platelets stick to collagen?
Through an intermediate molecule called Von Willebrand factor (vWF)
What is vWF produced by?
Platelets and Endothelial cells
What does vWF do?
Binds platelets to collagen
What happens once Platelets bind to Collagen?
The platelets become activated and expose various receptors
What do the receptors on Platelets allow it to bind to?
Plasma proteins called fibrinogen
What does Fibrinogen allow when it binds to platelets?
It allows more platelets to stick to the first ones that stuck to the vWF
What is the order of clotting with platelets in a blood vessel?
Platelets stick to vWF which binds to collagen, and then another later of platelets that bind to the first layer and then more platelets on top of that
What can be secreted by Activated Platelets?
- 5HT
- TXA2
- ADP
- PL
Which substances secreted by platelets cause Vasoconstriction?
5HT and TXA2
Which substances secreted by platelets causes further platelet aggregation?
- TXA2
- ADP
- Pl ➡️ Thrombin
Which substance secreted by platelets causes both Vasoconstriction and Further platelet aggregation?
TXA2
What is TXA2 supported by when it causes further platelet aggregation?
ADP and the presence of phospholipids on the surface of platelets
