Platelets Flashcards
What are the 3 components needed for hemostasis?
- Vessel wall
- Platelets
- Coagulation system
What are platelets responsible for?
Primary hemostasis
What are the 4 steps of primary hemostasis
- Adhesion to collagen at the site of vascular injury
- Additional platelets to plug the leak of the wall
- Release of platelet contents to promote hemostasis
- Provision of a phospholipid surface to assemble proteins of the coagulation cascade
Describe step 1…
-Adhesion of platelets to collagen at the site of vascular injury
- When the endometrium is disrupted, the collagen is exposed
- Platelets adhere to endothelial cells based on reaction between glycoprotein 1B and VonWillebrand Factor
Describe Step 2…
-Aggregation of additional platelets to “plug” the leak in the blood vessel
- Platelets activate other platelets to bind soluble molecules such as fibrinogen
- Fibrinogen acts like a bridge between the interacting platelets and the activated platelets at the binding site
What are platelets rich in that promotes hemostasis?
- ADP
- ATP
- Calcium
- Enzymes
- Clotting factors
The combination of what 2 things results in vasoconstriction?
- Clotting factors
- Prostaglandin Thromboxane A2
What is the point of vasoconstriction?
Controls bleeding
What is the goal of the phospholipid membrane?
-Organizes and promotes interactions and clotting factors
What does the assembly of a complex do?
-Enhances hemostatic activity and stops bleeding
When is the patient at risk for hemorrhage?
If they have problems with platelets, wall, or cascade
What is the normal platelet count?
150,000-400,000
When are platelet numbers a problem with surgery and trauma?
Under 50
When are platelet numbers a problem with spontaneous bleeding?
Under 20
