Haemotology 2 - platelets

Question 1

what are the 3 componenents of haemostatic reposnse

Answer 1

Vasocontstriction
Platelet adhesion and aggregation
Clotting - coagulation phase

Question 2

Features of platelets

Answer 2

small, oval, no nucleus
2-3micrometres

contains granules
megakaryocyte cytoplasm

lifespan 7-10 days

essential for haemostasis

Question 3

what is the desired end result after cogaultion phase?

Answer 3

conversion of soluble plasma protein to insoluble rigid fibrin

Question 4

Process of initiation of coagulation phase (EXTRINSIC PATHWAY)

Answer 4

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

Question 5

Process of initiation of coagulation phase (INTRINSIC PATHWAY)

Answer 5

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

Question 6

Process of common pathway

Answer 6

FXa and its co-factor FVa
Activates prothrombin to form THROMBIN

THROMBIN converts FIBRINOGEN to FIBRIN

Question 7

How would a Ca or K deficiency affect someone whoe gets an injury

Answer 7

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)

Question 8

Why might babies be at risk of haemorrrage?

Answer 8

Liver not fully formed
Usually vitamin K deficient

Usually given Vit K supplements to prevent haemorrage

Question 9

what are 2 ways the body controls clotting

Answer 9

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)

Question 10

What is the process of breaking down the fibrin clot? and what enzyme is needed?

Answer 10

Fibrinolysis
Enzyme = plasmin -> produces fibrin

produces fibrin degrading products

Question 11

explain structure of Group A Blood cell

Answer 11

Has A antigen

Has Anti-B antibodies in blood

Question 12

explain structure of Group B Blood cell

Answer 12

Has B antigen

Has Anti-A antibodies in blood

Question 13

explain structure of Group AB Blood cell

Answer 13

Has both AB antigens on surface

Has no antibodies in blood

Question 14

explain structure of Group O Blood cell

Answer 14

Has no antigens on surface

has anti A and anti B antibodies in blood

Question 15

What would happen if antibodies came into contact with the corresponding antigen on a RBC

Answer 15

agglutination
hemolysis

Question 16

which blood group genes are dominant and recessive

Answer 16

A and B are dominant

O is recessive

Question 17

Which blood group is the universal donor and universal recipient

Answer 17

O = universal donor

AB = universal recipient

Question 18

What happens if someone has the D antigen

Answer 18

Rh positive

Question 19

which alleles do you need to be Rh -ve

Answer 19

inherit 2 negative alleles

Question 20

How might a Rh -ve person end up with anti RhD antibodies

Answer 20

via sensitisation, so by exposure to Rh +ve RBCs

e.g.
transfusion
or pregnancy/birth (Rh -ve mum and Rh +ve baby)

Question 21

what can mixing of the bloods in a Rh -ve mum and Rh +ve baby cause

Answer 21

haemolytic disease of the newborn (HDN)

Question 22

what can caue mixing of the foetal and maternal blood

Answer 22

usually stays seperate throughout pregnancy
but during delivery
breakdown of placental tissue
causes mixing of foetal and maternal tissue

Question 23

in a Rh -ve mum and Rh +ve baby, what happens if the blood mixes and explain HDN

Answer 23

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