Exam 4 COPY 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)
Describe what is occurring during the common coagulation pathway.
- Prothrombin Activator and Ca2+ -Catalyzes the conversion of Prothrombin to Thrombin 2. Thrombin -Soluble Fibrinogen + Ca2+ = Insoluble Fibrin Threads Positive feedback effects -Accelerates formation of Prothrombinase -Activates platelets to release phospholipids
Describe what is occuring during step 4 of hemostasis- clot retraction and blood vessel repair.
Blood clot plugs the ruptured area of blood vessel Platelets pull on fibrin threads causing clot retraction Actin and Myosin -Squeezes serum from the blood clot blood clot shrinks Trapped platelets release factor XIII stabilizing the fibrin threads Edges of damaged vessel are pulled together Fibroblasts and endothelial cells repair the blood vessel
What are the two normal hemostatic control mechanisms?
- Fibrinolytic system 2. Anticoagulants Present In Blood to Prevent Intravascular clotting
What is the function of plasminogen?
Becomes Plasmin (Fibrinolysin) which digests fibrin threads
What is the function of Plasmin?
digest fibrin threads
Is plasminogen an active or inactive enzyme?
inactive
Is plasmin an active or inactive enzymes?
active
What is the function of prostacyclin produced by wbc’s and endothelial cells?
Opposes thromboxane A2 Inhibits platelet adhesion and release
What is a thrombus?
Blood Clot Decreased blood flow allows clotting factors to build up locally activates coagulation cascade
What is a embolus?
Thrombus may dissolve spontaneously or dislodge and travel Blood clot, air bubble or fat from broken bone in the blood
What are the vitamin K dependent clotting factors?
Factors II (Prothrombin), VII, IX and X
Where are the vitamen K clotting factors produced?
hepatocytes