Haematology Flashcards
Haemoglobin structure
- 4 polypeptide chains and 4 haem groups
describe the haem group
what happens when oxygen binds
Haem consists of protoporphyrin ring and Fe group bound to 4 N atoms,it also has a histidine residue
the Fe2+ can make 2 bonds for o2 on either side of the plane
once oxygen binds to the haem groups it goes form the deoxyghaemologbin to the oxyhaemoglobin configuration, this involves the movement of the FE into the plane upwards pullign with it the histidine residue , this is because oxygen is very electrogenative and pulls the cloud of electron density towards itself
this movement causes a small change in overall protein conformation
describe this curve myoglobin vs hb
-M has higher affinity for oxygen whilst the heamoglobin exhibits cooperative binding, which means that once 1 oxygen binds, its easier for the other oxygens to bind
describe this curve fetal
fetal hb has a higher afffinity for oxygen than the mother’s hb due to the less avid binding of 2,3-BPG, this allows fetal HB toextract o2 from materal hb across the placenta
where does fetal erythropoeisis occur
yolk sac (3-8 weeks)
liver (6 weeks - birth)
spleen (10-28weeks)
bone marrow (18wks-adult)
young liver synthesises blood
Blood types
(antigens on surface, antibodies, donate from, donate to)
what happens if you donate to wrong b type
A B AB O
Anti B(IgM) Anti A(IgM) none Anti A + B (IgG + IgM)
AO B O A B O AB O
A AB B AB AB A B AB O
haemolytic reaction
whats special about the membranes of erythrocytes
they have Hco3-/cL- antiporter aallowing RBC to export HCO3- and transport co2 from periphery to the lungs for elimination
poikilocytosis
varying shapes
describe what this is? what are the stains used and how do they differ? why is this cell present? how do i calculate the amount of this cell there is? and if it appears ‘x’ what do you do?
reticulocyte
in Wrights stain (normal) they appear macrocytic and hypochromic with little RNA, but with fluroscnt dyeyou can see the ribosomal RNA
its a sign of boen marrrow functioning as a result of erythroid proliferation, this may be due to acute blood loss
reticulocyte % = patient Hct/ actual HCt (usually 45%) (normal RI = <3%, [with anaemia less than 3 = bone marrow not funcitoning, and more than 3 = haemolytic lysis])
with polychromasic you do the RI / 2 and if that is less than 3% then issue as above
poikilocytosis varying shapes
anisocytosis
sizes vary
anisocytosis varying sizes
polycythemia vera
polycythemia vera
what are these cells? how are they made? whats their lifespan? describe how they are activated?
- thrombocytes
- thrombopoietin stimulates megakaryocytes to synthesis them
- 8-10 days
- endothelial damage, they then aggreagate to form a platelet plug
where does the location of platelet storage in organ ‘x’, and why does it lead to ‘y’ surgery?
1/3 of thrombocytes are stored in the spleen and so patients with immune
what do platelets contain
C A S H - wc is released upon activation
Ca2+ (important for binding of the coagulation factors) , ADP, Serotonin (c platelet aggregation and Vasoconstriction of injured vessel wall) , Histamine
it also contains alpha granules wc are vWF, fibrinogen, fibrin, platelet facotr 4
what are platelets activated by
- ADP (wc is also released by platelets ; it interacts with the P2Y1 P2Y12)
- Thrombin (wc informs platelets that clotting sequence is activated)
- Thromboxane A2 a powerful platelet aggregator wc is also released by platelets
- Collagen fibres (within extravascular surfaces)
what happens when platelets are activated
- stick to the exposed endothelium via vWF (wc helps them adhere to the membrane since its concentrated at exposed membrane)
- aggregate with other platelets and forms primary platelet plug wc is very weak. this primary platelet plug consists of activated platelets sticking to injured vessel and the connective tissue outside it.
- platelets undergo a conformational change and become sticky spiny spheres
- they then secrete factors from platelet granules e.g fibrinogen, ADP, thromboxane A2
what are most cofactors and describe the synthesis of some?
- most are proenzymes and so when functioning require co-factors like ca2+ and phospholipids
take too much warfarin
dangerous because inhibiting VIT K (vit k epoxidase reductase) and so carboxylation of the glutamate residues of cofactors 2 9 10 7 can’t occur and so they dont form carboxyglutamate and aren’t attracted to the positive ca2+ released
treatment is;
- give vit k to reverse warfarin
- if severe bleeding give vit k + FFP (fresh frozen plasma) / PCC (prothrombin complex concentrate) (wc is just the serum part of blood and contains clotting factors)
*
how is vit k made?
by enteric bacteria
and so neonatals that lack this enteric bacteria must be given vit k early on to prevent neonatal vit k deficiecny
anticoagulation and coagulation factors
coagulation factors
- all cofactors
anticoagulation factors
NATURAL
- protein s and protein c
- antithrombin
SYNTHETIC
- heparin (works by enhancing the activity of antithrombin)
- lwmh like enoxaprin, dalteparin
- direct factor Xa inhibitor apixaban
- fondaparinux (similar to heparin used for DVT)
describe and draw the whole pathway for bloodclotting
- intrinsic pathway is triggered by negatively charged surfaces ( like glass tube with scientists used to experiment with,blood still clots but theres no damage to endothelium - the reason it clots is the negatively charge surface)
describe how anticoagualtion occurs
- protein s and c made in the liver and works to cleave and inhibit facotr 8a and 5a
- antithrombin inhibits thrombin (IIa) and factors VIIa, IXa, Xa, XIa, XIIa
heparin enhances the activity of antithrombin
what happens to the fibrin clot soon after its formed
-platelets die; as they die actin-myosin filaments in the fibrin contract causing the wound to close up, (also due to the contraction you push fluid out the clot toughening it up)
what happens to the fibrin clot post repair
fibrinolysis
- macrophages recognise adn break down the fibrin clot adn it is destroyed by plasmin (the enzyme that is responsible for fibrinolysis)
its broken down into D-dimers and FDP (fibrin degradation products)
then it undergoes fibrous repair adn becomes replaced by granulation tissue and then a tiny scar
PLASMIN
made by the liver as plasminogen then acitvated by tissue plasminogen activator tPA wc circulates the blood
the other 2 plasminogen activators are ;
- streptokinase (found in streptococci)
- urokinase (found in urine)
they workby breaking down fibrin mesh
- tPA is prefered to streptokinase as an antithrombotic because it has a higher affinity for fibrinogen than strep. and also because its not antigenic (produce antibodies) so can be given more than once
which is better tPA or streptokinase and why?
whats a side effect of these drugs
tPA because not antigenic (since it doesnt come from a bacteria it doesnt cause antibodies to be made)
tPA has higher affinity for fibrinogen than streptokinase
bleeding more readily in the gums, or nose, or sometimes in the brain
what happens after surgery in terms of acitivity of members of the coagulation family
decreased activity of fibrinolytic activity wc remains low for 7-10days which coincides with the time period where many thrombi are formed postoperatively
what are the 3 coagulation pathways and how do you measure them?
intrinsic , extrinsic then complementary/combined pathway
I = APTT
E= PP
I to Ia = TT
Haemophilias
A = factor 8 deficicency XR
B = factor 9 defiency XR
C = factor 11 defeiecnecy AR
coagulation factor disorders aquired and congential
A ;
- liver disease
- vit K defiency
- anticoagulants
- Warfarin because it inhibits VitK
C
- Haemophilia A B
Haemphilias symptoms and treatements and how do they present in a blood test
Presentation in bloodtest:
- prolonged PT time
Symptoms ;
- haemarthroses (bleeding into joints)
- mucousal bleeding
- epistaxis (nose bleeding)
- prolonged bleeding from cuts, dental work
- bleeding excessively post trauma
treatment for HA = Inject with factor 8
treatment for HB = inject with FActor 9