lecture 6 - platelets Flashcards
What are the 2 components of haemostasis/stopping bleeding?
Platelets, coagulation
When will platelets adhere to endothelial cells?
Only when they are damaged, when underlying collagen and von Willebrand factor are exposed
What are the 2 key platelet receptors that are involved in the initial adhesion and activation of the platelets?
Collagen receptors, von Willebrand Factor receptors
What do platelets secrete to recruit more platelets to the site of injury?
Thromboxane, ADP
What substance is released from platelets’ granules and acts to vasoconstrict and recruit neutrophils via chemotaxis?
Serotonin
How is COX-1 involved with platelets?
COX-1 aids in production of thromboxane (TXA2), which is vital for the stimulation of adjacent platelets to form the platelet plug
How does aspirin impact on the functions of platelets?
It acts as in irreversible COX-1 inhibitor, meaning it prevents the release of thromboxane, inhibiting the formation of the platelet plug, as thromboxane is essential to recruitment of platelets.
Why does aspirin have a bigger effect on platelets than most other NSAIDs?
Most are reversible COX-1 inhibitors, meaning they only inhibit thromboxane production for the time they are in the system (less than a day), while aspirin permanently inhibits COX-1 for the lifetime of the cell
What is a common anti-platelet drug used in patients with an MI?
Clopidogrel
Where are platelets produced?
Formed with megakaryocytes in the bone marrow
What protein stimulates platelet production?
Thrombopoietin
What is the term for a low platelet count?
Thrombocytopenia
What are the visible signs of thrombocytopenia?
Tiny spots of bleeding under the skin - petichiae, or larger bruises
What are some of the key causes of a thrombocytopenia?
marrow depression/failure (leukemia, drugs, etc.), autoimmunity, disseminated intravascular coagulation, splenomegaly
