Lecture 10 Flashcards
RBC surfaces are marked by
glycoproteins and glycolipids
Based on 2 glycolipid isoantigens called
A and B found on the surface of RBCs
Plasma contains
isoantibodies or agglutinins to the A or B antigens not found in your blood
Antigen was discovered in blood of
Rhesus monkey
People with Rh agglutinogens on RBC surface are
Rh+.
Antibodies develop only in
Rh- blood type & only with exposure to the antigen
Transfusion reaction upon 2nd exposure to the antigen results in
hemolysis of the RBCs in the donated blood
People with type AB blood called
universal recipients
People with type O blood cell called
universal donors
Hemostasis:
Stoppage of bleeding in a quick & localized fashion when blood vessels are damaged
Hemostasis prevents …
hemorrhage
Methods utilized for hemostasis:
vascular spasm
platelet plug formation
blood clotting
Platelets store a lot of chemicals in
granules needed for platelet plug formation
Platelet Plug Formation -Steps in the process
(1) platelet adhesion
(2) platelet release reaction (3) platelet aggregation
Platelet Adhesion:
Platelets stick to exposed collagen underlying damaged endothelial cells
Platelet Release Reaction:
- Platelets activated by adhesion
- Extend projections to make contact with each other
- Release thromboxane & activate other platelets
- Thromboxane is also a vasoconstrictor decreasing blood flow
Platelet Aggregation- Platelet plug:
Activated platelets stick together and activate new platelets to form a mass
Plug reinforced by
fibrin threads formed during clotting process
Three Pathways of Clotting:
- Extrinsic Pathway
- Intrinsic Pathway
- Final Common Pathway
Extrinsic Pathway: damaged tissue leak
tissue factor into bloodstream
Extrinsic Pathway: Prothrombinase forms in
seconds
Extrinsic Pathway: in the presence of Ca+2 clotting factor X combines with
V to form prothrombinase
Intrinsic Pathway: Activation occurs when…
endothemlium is damaged
platelets are damaged –> release phosolipids
Intrinsic Pathway: Requires…
several minutes for reaction to occur
Intrinsic Pathway: Substances involved
Ca+2 and clotting factors XII, X and V
Final Common Pathway involves:
Prothrombinase and Ca+2
Thrombin
Final pathway: Prothrombinase and Ca+2
prothrombin to thrombin
Final pathway: Thrombin
presence of Ca+2 –> converts soluble fibrinogen to insoluble fibrin threads
Role of Vitamin K in Clotting:
- Normal clotting requires adequate vitamin K
- 4 clotting factors by hepatocytes (II, VII, IX, X)
- Produced by bacteria in large intestine
Intravascular Clotting:
Thrombosis
Embolus
Thrombosis:
clot (thrombus) forming in an unbroken blood vessel
Embolus:
clot, air bubble or fat from broken bone in the blood
Hemophilia:
Inherited deficiency of clotting factors
3 Hemophilias:
A, B, C
Hemophilia A:
lacks factor VIII (males only)
-most common
Hemophilia B:
lacks factor IX (males only)
Hemophilia C
(males & females)
-less severe because alternate clotting activator exists
Treatment of Hemophilia:
Treatment is transfusions of fresh plasma or concentrates of the missing clotting factor
