Exam 4 Flashcards
Define hemostasis. .
-Process which causes bleeding to STOP Prevents hemorrhage (massive decrease in blood volume)
Describe step 1 of hemostasis- vascular constriction
a. Local myogenic spasm b. Local autacoid factors from the traumatized tissues and blood platelets c. Nervous reflexes
Where are thrombocytes formed?
red bone marrow
Thrombocyte production is regulated by?
Thrombopoietin (liver and kidney)
List the contents/functions of thrombocyte membrane receptors and cytoplasm.
Adhesion proteins- vWF, fibronectin, collagen, fibrinogen Actin and myosin Phospholipids
Which substances activate platelets?
1.ADP released from damaged erythrocytes 2.Exposed collagen fibers 3.Thromboxane A2
What are the antithrombotic (anti-platelet) properties/functions of the endothelium?
1.Covers highly thrombogenic basement membrane -Uninjured endothelium does not bind platelets 2. PGI2 (prostacyclin) and NO from uninjured endothelium inhibit platelet binding 3. ADPase counters the platelet aggregating effects of ADP
Describe step 2 of hemostasis- platelet plug formation.
- Platelet adhesion -Subendothelial protein layer exposed -Platelets bind to subendothelial vWF, and collagen via surface glycoproteins -Platelets swell 2. Platelet release reaction -Release platelet agonists from granules 3. Platelet aggregation
Blood Coagulation.
Blood Clotting (Step 3 of hemostasis)
What is a blood clot?
1.Blood that has been converted from a liquid to a solid state 2. Formed elements trapped in insoluble fibrin threads
List the substances required for blood clotting.
Ca2+ Enzymes synthesized by liver cells Substances released by platelets or damaged tissues
Why is blood coagulation described as a cascade of reactions?
Each clotting factor activates the next in a fixed sequence
What is the end result of blood coagulation?
formation of insoluble fibrin threads
Describe step 3 of Hemostasis: Blood Coagulation
3 pathways 1. Extrinsic 2.Intrinsic 3. Common
Type of damage that activates the extrinsic pathway?
Tissue Trauma causes tissue factor (thromboplastin to leak into the bloodstream)
Type of damage that activates the intrinsic pathway?
endothelial damage occurs and platelets come in contact with exposed collagen fibers Phospholipids are released from damaged platelets
What ion activates the clotting factors in the extrinsic pathway?
Ca2 and clotting factors combine to create Prothrombin Activator (Prothrombinase)
What ion activates the clotting factors in the intrinsic pathway?
Ca2+ and clotting factors combine to form Prothrombin Activator (Prothrombinase)
Prothrombin activator forms in seconds or minutes in the extrinsic pathway
Prothrombin Activator forms in seconds Faster process
Prothrombin activator forms in seconds or minutes in the intrinsic pathway
Prothrombin Activator forms in several minutes
Is Less or More steps involved in the extrinsic pathway?
Less
Is Less or More steps involved in the intrinsic pathway?
More
What enzyme is produced at the end in the extrinsic pathway?
Prothrombin Activator (Prothrombinase)
What enzyme is produced at the end in the intrinsic pathway?
prothrombin Activator (Prothrombinase)