Blood pt 3 (Platelets) Flashcards
What is the lifespan of a Platelet?
about 10 days
What is platelet formation regulated by?
The hormone thrombopoietin (LIVER AND KIDNEY)
about how many platelets are in the blood?
150,000 - 400,000
Life cycle of a platelet?
- Hematopoietic stem cell (hemocytoblast)
- Developmental pathway
a) Megakaryoblast (stage 1) - Small
b) Megakaryocyte (stage 2/3) - medium
c) Megakaryocyte (stage 4) - big - Platelets
HEMOSTASIS!
Stoppage of bleeding
What are the three steps involved in Hemostasis?
- Vascular spasm
- Platelet plug formation
- Coagulation
Vascular spasm
This is a vasoconstriction of vessel in response to damage
Why have a vascular spasm?
It reduces blood flow through the artery, sending less oxygen than normal to nearby tissues.
Platelet plug formation
- usually, platelets do not stick to each other or to endothelial linings. However, in the PPF, NO and PGI2 stop producing as much therefore allowing the platelets to stick together.
- exposed collagen - platelet adhesion
Von Willebrand factor
A large plasma protein - helps adhesion by forming a bridge between collagen and platelets
What is the PPF an example of?
a Positive feedback cycle
Coagulation
- blood is transformed from liquid to gel
- reinforced PP with FIBRIN threads
- series of reactions use CLOTTING FACTOR - PROCOAGULANTS, mostly plasma proteins
How many phases are there in Coagulation?
3!
What are the three phases in coagulation?
- Prothrombin Activator formed
- Prothrombin to Thrombin
- Fibrinogen molecules –> fibrin mesh
How are the procoagulants numbered?
I to XIII in order of discovery
