Haemotology 2 - platelets Flashcards
what are the 3 componenents of haemostatic reposnse
Vasocontstriction
Platelet adhesion and aggregation
Clotting - coagulation phase
Features of platelets
small, oval, no nucleus
2-3micrometres
contains granules
megakaryocyte cytoplasm
lifespan 7-10 days
essential for haemostasis
what is the desired end result after cogaultion phase?
conversion of soluble plasma protein to insoluble rigid fibrin
Process of initiation of coagulation phase (EXTRINSIC PATHWAY)
Tissue factor (Factor III) released after damage occurs
Binds to Factor VII (w/Ca2+)
= Tissue Factor - FVIIa complex
This binds to FX to activate it = FXa
Process of initiation of coagulation phase (INTRINSIC PATHWAY)
Activated proenzymes (usually Factor XII)
Combine with Platelet Factor and Ca2+
Then combine with Clotting Factors - Factor IX and co-factor VIII
Activates FX -> FXa
Slower than the extrinsic pathway
Process of common pathway
FXa and its co-factor FVa
Activates prothrombin to form THROMBIN
THROMBIN converts FIBRINOGEN to FIBRIN
How would a Ca or K deficiency affect someone whoe gets an injury
impairs blood clotting
Ca2+ usually incolved in speeding up the process and activates
Vit K needed to produce certain clotting factors in liver (ie prothrombin)
Why might babies be at risk of haemorrrage?
Liver not fully formed
Usually vitamin K deficient
Usually given Vit K supplements to prevent haemorrage
what are 2 ways the body controls clotting
natural anticoaglulants:
- Antithrombin - inhibits thrombin among others
- Heparin - released by basophils (type of WBC) and mast cells = co-factor that accelerates Antithrombin
(can get it as a drug)
What is the process of breaking down the fibrin clot? and what enzyme is needed?
Fibrinolysis
Enzyme = plasmin -> produces fibrin
produces fibrin degrading products
explain structure of Group A Blood cell
Has A antigen
Has Anti-B antibodies in blood
explain structure of Group B Blood cell
Has B antigen
Has Anti-A antibodies in blood
explain structure of Group AB Blood cell
Has both AB antigens on surface
Has no antibodies in blood
explain structure of Group O Blood cell
Has no antigens on surface
has anti A and anti B antibodies in blood
What would happen if antibodies came into contact with the corresponding antigen on a RBC
agglutination
hemolysis
which blood group genes are dominant and recessive
A and B are dominant
O is recessive
Which blood group is the universal donor and universal recipient
O = universal donor
AB = universal recipient
What happens if someone has the D antigen
Rh positive
which alleles do you need to be Rh -ve
inherit 2 negative alleles
How might a Rh -ve person end up with anti RhD antibodies
via sensitisation, so by exposure to Rh +ve RBCs
e.g.
transfusion
or pregnancy/birth (Rh -ve mum and Rh +ve baby)
what can mixing of the bloods in a Rh -ve mum and Rh +ve baby cause
haemolytic disease of the newborn (HDN)
what can caue mixing of the foetal and maternal blood
usually stays seperate throughout pregnancy
but during delivery
breakdown of placental tissue
causes mixing of foetal and maternal tissue
in a Rh -ve mum and Rh +ve baby, what happens if the blood mixes and explain HDN
when blood mixes
mum’s immune system mounts a response against the Rh+ve antigens
But usually at delivery there’s no time for them to react (usually takes 72hrs)
But the antibodies remain in the blood
So in first pregnancy theres no impact
BUT
In second, antibodies are already there
in second, when blood mixes, it can cause immune response and causes haemolytic disease of newborn
