Blood Flashcards
What are the functions of blood
Maintain homeostasis (body temp, pH, fluids etc.), transport, immune system, regulate blood clotting, remove toxins
What are the 4 main components of blood
Plasma, Erythrocytes (RBC), Leukocytes (WBC), thrombocytes (platelets)
Where is the vast majority of blood at rest
Venous system
What % of the blood is plasma
Around 55%
What % of the blood is leukocytes and platelets
1%
What percentage of the blood is erythrocytes
44%
What is the haematocrit
The percentage of total blood volume that is RBC
What makes up the buffy coat in a test tube of separated blood
WBC and platelets
What is the lightest and heaviest components on the blood
Lightest= plasma, heaviest = RBC
What is the function of plasma
90% water so used for transport and thermoregulation as (water has a high capacity so used to hold, distribute and release heat generated within tissues)
What does plasma consist of
Water, plasma proteins, nutrients, waste products and dissolved gases
How are plasma proteins identified in a lab
Electrophoresis- different plasma proteins have different electrical charge
Why is it useful to identify changes in plasma proteins
Used to identify abnormal patterns related to clinical conditions
What are the two benefits of the indented disc shape of RBC
1) provides a larger surface area for O2 diffusion
2) thin so rapid diffusion of O2
Why is mean cell volume an important clinical index
Used in diagnosis e.g. type of anaemia
What are microcytic RBC and what type of anaemia are the associated with
Small RBC associated with iron deficiency anaemia
What are macrocytic RBC and what type of anaemia are they associated with
Large RBC associated with folate deficiency anaemia
What are the two parts of haemoglobin
4 chain protein (globin part) and four iron containing haem groups
What are the 4 forms of the globin proteins in haemoglobin
Alpha, beta, gamma and delta
Which globin proteins combination are most common
2 alphas, 2 betas (97% of adults)
What does each haem group consist of
A porphyrin ring that contains one iron atom
How many molecules of O2 can haemoglobin carry
4 as each iron atom in haem can combine reversibly with one molecule of oxygen
Why is the majority of oxygen in the blood bound to haemoglobin
As oxygen is poorly soluble in plasma
What is haem and why does it appear red when oxygenated and blue when deoxygenated
Haem is a pigment and the different colours are due to it’s iron content
What 2 factors determine Hb’s ability to bind to O2
Partial pressure of O2 and number of available binding sites
Why does Hb unload more oxygen to tissues during oxygen
Lower PO2 in tissues due to increased metabolic demand
Other than O2 what else can bind to haemoglobin
Carbon dioxide, H+ component of carbonic acid, carbon monoxide
What are haemoglobinopathies
Diseases that promote abnormal haemoglobin production e.g. sickle cell anaemia
What causes sickle cell anaemia
Mutated gene coding for beta globin chain in Hb results in amino acid change (glutamic acid to valine), therefore Hb polymerises at low pO2 sp long crystals of HbS form (sickle shaped RBC are produced)
What are the problems associated with sickle cell anaemia
RBC become trapped in small vessels due to shape and block them which deprives downstream tissues and results in ischemia (reduced O2 levels) and infarction (tissue death)
What are the 4 blood groups
A, B, O, AB
What is an antigen
A molecule that can induce an immune response
What can antigens consist of
Proteins, glycoproteins and glycolipids
What is a blood group
A classification based on the presence of inherited antigenic substance on the surface of a RBC
What antibodies and antigens do type A have
Anti-B bodies and A antigens
What antibodies and antigens do type B have
anti-A bodies and B antigen
What antibodies and antigens do type AB have
No antibodies and A and B antigens
What antibodies and antigens do type O have
Anti- A and anti-B bodies and no antigens
Which group are universal recipients and why
AB as can receive blood from any ABO group without developing a haemolytic transfusion reaction
Which group are universal donors
O and blood can be given to any ABO group without triggering a haemolytic transfusion reaction as no antigens to triggers response
What is a haemolytic transfusion reaction
Where the recipients RBC will agglutinate an lyse if they have antibodies against them in their blood
What is used to determine blood type
ABO blood group system and the presence/ absence of the Rhesus D antigen
Are blood groups permanent
Mostly yes as they are inherited however infection, malignancy, autoimmune disease or after bone marrow transplant may cause it to change
What is haemostasis
The arrest/ stop of bleeding from a broken blood vessel controlled by haemostatic mechanisms
Where are haemostatic mechanisms most effective and why
Arterioles, venules and capillaries as slower flow velocity
What are platelets
Small cell fragments (anuclear) that have budded off the outer edges of large bone marrow cells (megakaryocytes)
What are the three steps of haemostasis
Vascular spasm, formation of a platelet plug and blood coagulation
What occurs during vascular spasm
A temporary measure where the smooth muscle layer surrounding a damaged blood vessel constricts immediately to slow blood flow and minimise loss, damaged cells and platelets release vasoconstrictors (ADP and serotonin etc.) and the ends of the endothelial surfaces are pushed together and adhere to each other
How is a platelet plug formed
1) platelets stick to the exposed collagen made visible by the damaged endothelium
2) platelets stick to eachother using von willebrands factor (a plasma protein)
3) bound platelets realesse ADP, 5HT and Thromboxane A2 which causes the platelets to be become sticky and adhere to eachother causing a rapid build up of platelets at the site, sealing the platelet plug for further compaction, vasoconstriction and the release of clotting factors
What is the role of prostacyclin in blood clotting
Inhibits platelet aggregation so the platelet plug is limited to the defect and does not spread to normal tissue
What occurs during blood coagulation
The blood clot forms on top of the platelet plug and reinforces it, fibrinogen (a large soluble plasma protein) converted into fibrin (an insoluble thread like molecule) which RBC become enmeshed in the fibrin plug
Describe the clotting pathway and the plasma proteins (factors) involved
Fibrinogen is converted to fibrin monomers by thrombin (protease), fibrin monomers are converted to a fibrin polymer by factor XIIIa and Ca++, which forms the clot
What are the two anticlotting systems
Anti-thrombin and thrombomodulin (proteins C and S)
What does anti-thrombin do
Inhibits many of the clotting factors (esp thrombin), it’s activity is enhanced by heparin which is normally present on endothelial cells
What is the role of thrombomodulin
Expressed by endothelial cells and binds to thrombin to eliminate its coagulant effects and activate protein C
What is fibrinolysis
The breakdown of a fibrin clot (usually after healing)
What is a thrombus
A blood clot within a vessel/heart
What is an embolus
Detached mass able to travel in a blood vessel
What is an embolism
The lodging of an embolus
What is thrombo-embolism
Blockage by a thrombus that has travelled
What is Virchow’s triad
3 things that could lead to abnormal thrombus formation in the body (blood stasis/inefficient circulation, changes to vessel wall and thrombogenic changes in blood e.g hypercoagulation)
Inflammatory factors are a modern day addition
What is von willebrand,s disease
Lack of von willebrand factor leading to poor platelet aggregation
What factor is deficient in Haemophilia A and B
A- VIII, B- IX
