Lecture 24 Blood Types & Clotting Flashcards
Describe the stages of blood clotting and emphasizing the common pathway.
1 . First vasculospasm - (reduce blood flow) causes the muscular walls of the blood flow to contract, reducing the blood flow of injured sites.
- Williebrand factor - Exposed collagen of the walls of blood vessels initiate the clotting mechanism through the release of Williebrand factor from the endothelial cells.
- Platelet plug - platelects adhere to the free fibers through the the use of psuedopods draw together to form a platelet plug.
- Thromboxane A2 - The platelets degranulate and release Thromboxane A2 which promote further platelet aggregation and vaculoplasm by the vessel muscularis layer.
- Coagulation of Blood - Complex events, using one or two pathways, the extrinisc 15 second reaction time or intristic pathway 3 -6 min reaction time.
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Identify the factors that promote and inhibit blood clotting.
Factor I - Fibrinogen
Factor II - Prothrombin
Factor III - Thromboplastin
Factor IV -Calcium
Factor V - Labile factor or proaccelerin or accelerator globulin.
Factor VII - Stable factor of proconvertin
Factor VIII - AHF or AHG
Factor IX - Christmas factor plasma thromboplastic component.
Factor X - Stuart - Prower factor
Factor XI - Plasma thromboplastic antecedent
Factor XII - Hageman factor/glass factor/ contact factor
Factor XIII - Fibrin Stabilizing factor
Define clotting and bleeding times
The bleeding stops within 7 minutes by then the clot is formed and begins to repair. Blood clotting, or coagulation, is an important process that prevents excessive bleeding when a blood vessel is injured. Platelets (a type of blood cell) and proteins ( clotting factors) in your plasma (the liquid part of blood) work together to stop the bleeding by forming a clot over the injury.
Define the classification of the ABO and Rh blood groups.
This blood group contains two antigenic markers, A and B. o indicates the absence of any marker.
There are several antigens in this blood group, but only Rhd reacts strongly enough with the recipient blood to be of concern. So if Rhd is present the donor is Rh+. If Rhd is not present, the donor is Rh-.
Antibodies to Rh are not normally present in blood. If the recipient is Rh-, they must be first exposed to Rh before they produce antibodies.
Rh- women that give birth to Rh+ babies will have a normal first birth, but the baby’s blood will mingle with the mother’s blood during birth. As a result, she will make antibodies against Rh, and subsequent pregnancies will result in erythroblastosis fetalis.
Define the agglutination reaction as the basis for the ABO blood symptoms.
A can only take from A and O. B can only take from B and O. AB can take from three.
Describe common pathway
The activation of Factor X sets off a series of events that will actually form the clot. Factor X combines with Factor V in the presence of PF3 and Ca+2 to create Prothrombin Activator.
The inactive Prothrombin in the blood is converted to Thrombin, which converts the inactive Fibrinogen (also in the blood) to Fibrin.
Factor XIII and Ca+2 produce crosslinks between the Fibrin threads creating a meshwork (white thrombus). RBCs trapped in it fill up the spaces, producing the red thrombus (clot).
Describe intrinsic and extrinsic pathways
Extrinsic pathway - Initiated by tissue factor (Factor III), released by the surrounding tissues when a blood vessel is ruptured.
This combines with Factor VII to form a complex, which in the presence of Ca+2 can activate Factor X in the blood, initiating the Common Pathway.
The rate of this conversion is directly proportional to the amount of damaged tissue (an abrasion will clot faster than a scalpel cut)
Intrinsic - The presence of a rough or foreign agent within the blood vessel (e.g. atheroma) can initiate an internal clotting mechanism that does not involve the surrounding tissues. Since this will usually result in the occlusion of the vessel, the body makes it as complex as possible. Platelets release Factor XII, beginning the cascade.
Factor XII activates Factor XI, which in turn activates Factor IX.
Factor IX and Ca+2 activate Factor VIII, and this complex then activates Factor X of the Common Pathway.
How do clot retract?
Fibrin attacthes to the edges of the wound and pulls them in closer resulting in a smaller wound. Platelets and endothelium (inner wall of blood vessel) stimulate the adjacent fibroblasts to undergo mitosis, creating granulation tissue under the clot.
The dissolution of the clot (fibrinolysis) begins almost immediately, permitting the fibroblasts to infiltrate the wounded area and repair it.
Thrombolysis
Endothelial cells in the wounded tissue release tissue plasminogen activator(tPA).
Plasminogen, found in the blood plasma is converted to plasmin by tPA.
Plasmin dissolves the fibrin, which results in the dissolution of the clot.
If this process exposes damaged tissue, the process of clot formation is restarted, resulting in a dynamic equilibrium.
What is a blood type?
Presence of or absence of markup, or antigen, on the surface a persons RBCs.
