Lecture 9 - haemotology II Flashcards
Platelets: what are they, what are they involved in, how does production work, and how long do they last?
Pieces of large cells with small, oval nuclei about 2-3 microns in diameter containing granules involved in inflammation
Involved in blood clotting
Produced by megakaryocytes in the bone marrow. Production is stimulated by thrombopoietin from the liver.
7-10 days
Forming a stable hemostatic plug
Vessel injury leads to platelet activation, releasing serotonin, thromboxane A2, and ADP which leads to vasoconstriction and platelet adhesion. These two factors form the primary hemostatic plug
Tissue factors from the vessel injury along with the platelet phospholipid cause the blood coagulation cascade to start, which uses thrombin to convert fibrinogen into fibrin to form the final, stable hemostatic plug
Extrinsic pathway to the coagulation of blood
Tissue damage leads to tissue factor III reacting with calcium ions and clotting factors VII leading to factor VII (tissue factor complex)
Intrinsic pathway to the coagulation of blood
Tissue damage leads to activated proenzymes (usually factor XII) which react with calcium ions and platelet factor 3 clotting factors VIII and IX which leads to factor X Complex
The common pathway to the coagulation of blood
Factor X reacts with the factor X complex (FXa) and Factor VII complex (FVIIa) to produce prothrombinase which converts prothrombin to thrombin which converts fibrinogen to fibrin
Calcium’s important role in blood clotting
Affect almost every aspect of the clotting process
Any disorder that decreases the concentration of calcium ions will impair blood clotting
Vitamin K’s important role in blood clotting
Adequate vitamin K is necessary for the production of certain clotting factors in the liver including prothrombin
How is clotting controlled within the body?
The two main natural anticoagulants are antithrombin and heparin.
Antithrombin inhibits thrombin (and other factors) and heparin is produced by mast cells and basophils and it accelerates the action of antithrombin
How are clots broken down?
Fibrinolysis - plasmin enzyme produces things that degrade fibrin, breaking down the clot
A person of blood group A:
Potential allele combinations
Antigens on cells
Antibodies in the blood
A
IᴬIᴬ / Iᴬi
A
Anti-B
A person of blood group B:
Potential allele combinations
Antigens on cells
Antibodies in the blood
B
IᴮIᴮ / Iᴮi
B
Anti-A
A person of blood group AB:
Potential allele combinations
Antigens on cells
Antibodies in the blood
AB
IᴬᴮIᴬᴮ
AB
N/A
A person of blood group O:
Potential allele combinations
Antigens on cells
Antibodies in the blood
O
ii
O
Anti-A, anti-B
Rhesus group (D)
Either present (+) or not present (-)
