Blood Flashcards
What is the blood composed of and the percentages for each
Plasma 55%
Buffy coat >1%
Erythrocytes 45%
What are characteristics of erythrocytes
Biconcave
No nucleus, mitochondria or other cell organelles
Millions of haem molecules
No DNA
Cannot synthesise RNA
How big is an erythrocyte (approx)
6um
What is the average lifespan of an erythrocyte
120 days
What is blood typing
Blood typing is used to categorise individuals based on the presence or absence of antigens of the surface of the erythrocytes
What are white blood cells
White blood cells also known as leukocytes are the immune cells of the body
What are the 2 classification of leukocytes
Myeloid and lymphoid
What are the myeloid cells in the body
Neutrophils
Monocytes
Eosinophils
Mast cells
Basophils
What are the lymphoid cells in the body
T-cells
B-cells
Natural killer cells
What are neutrophils and what are there characteristics and function
They are the most common leukocyte in the body.
They are multi-lobed nuclei
There function is to phagatose at the site of inflammation
What is a monocyte and its function
Give 2 examples of monocytes in the body
Monocytes are diverse blood cells which can differentiate into macrophages and phagoctose potential pathogens.
When they differentiate they get specialised names
Eg- kupffer cells in the liver
Microglia in the CNS
What are eosinophils and what is there function
They are granular leukocytes which act as mediators to allergic reactions and cause immune response to parasitic infections
What are basophils and what is there function
Basophils are the least common leukocyte in the body
They cause an inflammatory reaction in the immune response to any allergic reactions
What is the function of B-cells
Produce circulating antibodies
What is the function of T-cells
Become cytotoxic, helper/suppressor cell mediator immune cells
Memory T-cells are there to remember the foreign body so when it invades again your body knows what to do
What is the function of natural killer cells
They eradicate virus infected cells
What is plasma
Plasma is the liquid portion of the blood often a straw yellow colour
What is the main component of blood plasma
Mostly water
What other things are found in blood plasma apart from water
Amino acids
Electrolytes
Gases
Nitrogenous waste
Nutrients such as glucose and fats
Proteins such as albumin, globulins, enzymes, clotting factors and hormones
What are platelets also known as
Thrombocytes
Where are platelets derived from
Megakaryocytes
What are platelets
They are cell fragments
What is the function of platelets
They are cells that are recruited by the site of injury within the body which they activate the clotting process to cause wound closure
What is the platelets role in immunity
They platelets interact with the antibodies which cause them to secrete pro inflammatory and procoagulant mediators which can connect the adaptive and innate immune responses
How do platelets cause wound closure at the site of injury in the body
Platelets adhere to the vascular wall of the damaged vessel and react with fibrin to build a solid clot over the open wound, this usually takes 1 to 3 minutes
What is the coagulation cascade
The coagulation cascade is a series of reactions catalysed by protein enzymes known as coagulation factors to produce fibrin which is used to help clot the blood at the site of injury
What is primary haemostatsis
The activation and adherence of platelets to the damaged endothelium and produce a vascular response to the injury such as vasoconstriction
What is secondary haemostatsis
This is the stabilisation of the active platelets due to the actions of strands of fibrin produced in the coagulation cascade
What are the 3 stages of the coagulation cascade
Extrinsic
Intrinsic
Common pathway
What is the extrinsic pathway of the coagulation cascade
This is the initiation of the coagulation cascade which is mediated by the release of tissue factors which are expressed on the surface of cells found outside the blood vessels but not in the circulating blood cells or the endothelium. When the tissue factor is released and comes into contact with the blood it combines with the circulating clotting factor, factor VII to form a complex. This complex leads to the activation of clotting factor X which triggers the start of the common pathway
What is the common pathway of the coagulation cascade
This stage is the final stage of the coagulation cascade which leads to the formation of thrombin and fibrin
This stage of the coagulation cascade begins with the activation of clotting factor X to clotting factor Xa via either the extrinsic or intrinsic pathways. Factor Xa then combines with clotting factor V, platelet membrane phospholipids and Ca2+ ions to convert prothrombin to thrombin. This then triggers fibrinogen to be converted into fibrin strands which are an important part of the structural component for the formation of a thrombus.
The production of thrombin also activates other parts of the coagulation cascade via a positive feedback loop, via the intrinsic pathway which leads to a thrombin burst (large amount of thrombin produced)
What is the intrinsic pathway of the coagulation cascade
This pathway is initiated by the common pathway by the positive feedback loop and the amplification of thrombin
This pathway is activated by surface contact, when damage to the vascular endothelium leads to exposure of the clotting factors to the negatively charged sub endothelial surface which is mediated by molecule kallikrein.
Reactions within the pathway
Surface contact activates factor XII
Factor XIIa activated factor XI
Factor XIa activates factor IX
Factor IXa combines with factor VIIIa, platelet membrane phospholipid and Ca2+ ions to activate factor X which then activates factor Xa and the common pathway
Why does the coagulation cascade need to be regulated
Without the cascade been regulated the positive feedback loop started by the production of thrombin would continue in the intrinsic pathway causing dangerous levels of clotting within the blood
What is used to inhibit aspects of the coagulation cascade to stop dangerous levels of blood clotting in the body
Various different proteins
Protein C- which is produced in response to thrombin which binds to the receptor on the vascular endothelium which leads to the activation of Protein S which causes the breakdown of clotting factors Va and VIIIa in a negative feedback loop.
Antithrombin- this is a natural anticoagulant which is produced by the liver which destroys clotting factors XIa, Xa and thrombin
Heparin and Fondaparinux- this enhances the natural effect of Antithrombin
Tissue factor pathway inhibitor protein- this binds to and inactivates clotting factors VIIa and Xa
What are the functions of erythrocytes
Gas exchange and transport (main function)
Determining blood type
Explain how erythrocytes perform gas exchange and act as transportation
Blood travels to the lungs where in the capillaries oxygen diffuses into the cell and bings to the haemoglobin forming oxyhemoglobin (this is what gives oxygenated blood is bright red colour). The oxygen rich erythrocytes travel through the arteries until it reaches the desired tissue.
Within the tissue the oxygen is released from the haemoglobin and diffuses across into the tissue. At the same time carbon dioxide from the tissues diffuse the opposite way and binds with the haemoglobin in the erythrocyte and form deoxyhaemoglobin (this is what gives deoxygenated blood its purple/blue colour). The deoxygenated erythrocytes then travel through the veins and back to towards the heart and lungs.
When they deoxygenated blood reaches the capillaries in the lungs the carbon dioxide is release and diffuses into the capillaries for it to be exhaled.
What is the function of a neutrophil
These are the first cells to respond to bacteria and viruses in the body.
They send signals to other immune cells
What is the function of eosinophils
They fight bacteria within the body
They respond to parasitic infections
They triggers allergy symptoms
What is the function of basophils
They play a role in asthma
They mount non-specific immune responses to pathogens
They release histamine
What is the function of B-Cells
Humoral immunity
Produce antibodies
Play a role in vaccinations
What is the function of T-Cells
They are are responsible for recognising specific foreign bodies and killing them
(Memory T-Cells)
What is the function of monocytes
Clean up dead cells
What is sickle cell anaemia
This is a disorder which causes the deformation of erythrocytes caused by the inheritance of sickle cell gene
What populations is sickle cell most common in
African and Caribbean
How does sickle cell anemia occur
Sickle cell anemia is caused by a single point mutation in the beta-globin gene which is inherited which results in an amino acid replacement at position 6 in the beta-globin chain. Glutamic acid is replaced with valine which results in sickle haemoglobin
What type or inherited disease is sickle cell
This is an autosomal recessive disease
What happens to an individual if they only inherit on sickle cell gene
They would only be a Carrier for the disease but would show many if any symptoms at all
What are some of the physiological stressors for sickle cell
Hypoxia
Dehydration
Infection
Cold temperatures
Acidosis
What happens when an individual with sickle cell experiences some of the physiological stressors
The sickled haemoglobin will polymerise and cause the erythrocytes to deform
What can cause an individual who has sickle cell that would need hospital admission
Sickle cell disease can cause vast-occlusive crises where by the sickled blood cells cause an obstruction in the micro circulation leading to pain and ischemia and even infarction.
Sickle cell disease can also cause acute chest syndrome
What can be done for an individual admitted to hospital with vaso-occlusive crises suffering with sickle cell
Medication such as crizanlizumab can be used to reduce obstructions and pain as it prevents the restriction of blood flow
What is thalassaemia
Caused by an individual producing little to no haemoglobin which causes anemia
What causes thalassaemia
The globin genes are absent or mutated which limits the ability to produce the globin chains. This causes a reduction in 1 of the certain types of chains and so an excess of the opposite chain. This accumulation of unpaired chains causes the erythrocytes to become unstable and so are unable to mature and so macrophages destroy them in the bone marrow. This destruction causes the body to produce more erythrocytes to compensate this but each one produces has a reduced amount of haemoglobin and so they become hypo chromic red cells and in severe cases can cause an insufficient oxygen delivery in the body
What are the 2 types of thalassaemia
Alpha-thalassaemia and beta-thalassaemia
What causes alpha-thalassaemia
Caused by the deletion of alpha globin gene located on chromosome 16.
If the gene is deleted in 2 different places this is known as alpha plus
If the gene is deleted in the same place this is known as alpha zero
If more than 2 genes are deleted this is known as haemogolobin H disease
What causes beta-thalassaemia
This is caused by deletion or mutation of the beta globin genes on chromosome 11
If only 1 copy of the gene is affected it is known as beta-thalassaemia minor
If both copies are affected this is known as beta-thalassaemia major
What is thrombocytopenia
When an individual has a low platelet count
Why could an individual have a low platelet count
This could be caused by
Reduction in platelet production
Reduction in platelet survival
Dilution of platelet numbers
What might cause a reduction in platelet production
Viral infections
Chemotherapy agents
Aplastic anemia
B12 deficiency
Excess alcohol use
Congenital conditions
What might cause a reduction in platelet survival
This can be caused by immune causes such as
Idiopathic thrombocytopenic purpura
Lupus
Rheumatoid arthritis
Non-immune causes
Medications
Splenomegaly
What is meant by pseudothrombocytopenia
This is where platelets clump together in the blood and so when the level of them is measured it causes a low reading but this is false
When was the first animal to animal blood transfusion
1666 by Richard Lower
In 1667 what did Jean Denis achieve in relation to blood transfusion
He was the first to achieve the first animal to human blood transfusion
When was the first human to human blood donation said to be done and by who
1818 by James Blundell
When we’re ABO blood groups discovered
1901
What surgical technique did Alexis Carell discover to aid transfusion between donor and recipient
He discovered anastomosis of the vessels between the donor and recipient to aid transfusion
What year was 0.2% sodium citrate discovered as an anticoagulant
1915
Where was the first blood donor service
London in 1921
When was NHS blood and transplant established
1948
In what year was cryoprecipitate developed and what does it treat
1964
To treat haemophilia
How many erythrocytes are released from the marrow every second
2-3 million
What are the 4 blood types
A
B
AB
O
Why is the ABO blood system known to be potently antigenic
Because the body is able to produce corresponding antibodies to each antigen naturally
How is blood type inherited
Following the Mendelian pattern occurring on chromosome 9
When does a body start to produce ABO antibodies
They start to produce them from birth however there numbers are very low and so are undetectable till at least 3-6 months
If a person is blood type A what type of antigen do they have present on the erythrocyte surface
A antigens
If a person is blood type B what antigen do they have present on the erythrocyte surface
B antigens
If a person is blood type AB what antigen do they have present on the erythrocyte surface
A and B antigens
If a person is blood type O what antigen do they have present on the erythrocyte surface
No ABO antigens would be present
What type of antibodies do individuals produce
Individuals generate antibodies to the antigens that are absent from the surface of the erythrocyte without prior exposure
What antibodies would an individual produce if they are blood type A
Anti-B antibodies
What antibodies would an individual produce if they are blood type B
Anti-A antibodies
What antibodies would an individual produce if they are blood type AB
Do not produce an ABO antibodies
What antibodies would an individual produce if they are blood type O
Anti-A antibodies
Anti-B antibodies
Anti-AB antibodies
Out of the ABO alleles which are dominant and recessive
A and B alleles are codominant
O is recessive and non-functional
Do the ABO alleles code for the antigens produced on the erythrocyte surface
No the ABO alleles do not code from the antigen, they code for the glycosyltranferase which adds sugars onto the protein precursor on the erythrocytes membrane to form the antigens
What is cross-matching and why is it done
Cross matching is a series of tests done of a patients blood sample and blood products to check there will be no agglutination reactions when the blood gets transfused
What is the most important Rh antigen
D-antigen
What is the D-antigen the most clinically important Rh antigen
Because its the most immunogenic
If an individual is Rh-pos will they have D antigens presence
Yes
Will an individual who is Rh-neg have D-antigens present
No
If a person doesn’t have D antigens present will they have anti-D antibodies
No unless they have had prior exposure
What are packed red cells
They are erythrocytes and additives
What type of packed red cells would an O patient receive
They can only receive O pRBC
What type of packed red cells would an A patient receive
They can receive A or O pRBC
What type of packed red cells would an B patient receive
They would receive either B or O pRBC
What type of packed red cells would an AB patient receive
They could receive AB, A, B or O pRBC
Why can anyone receive O pRBC
O-neg is the universal donor of packed red blood cells
Who do people need to receive ABO compatible blood during a red cell transfusion
Due to the body been able to naturally develop antibodies to antigens given
What antibodies can be given in Fresh frozen plasma to an O patient
They can have Fresh frozen plasma containing anti-A and anti-B antibodies
What antibodies can be given in Fresh frozen plasma to an A patient
They can receive fresh frozen plasma with anti-B antibodies
What antibodies can be given in Fresh frozen plasma to an B patient
They can receive anti-A antibodies
What antibodies can be given in Fresh frozen plasma to an AB patient
They can only receive fresh frozen plasma from donors who also have AB blood type as they have no antibodies in plasma
What is haemolytic disease in foetus and newborns
This is a blood disorder that affects baby’s due to them and their mother having different blood types and so the blood types mixing, new antibodies naturally been made and so the red blood cells causing a haemolytic reaction in the baby, and so fast breakdown of the erythrocytes
Explain what happens in haemolytic disease in foetus and newborns
The mother could be Rh-neg and the father could be Rh-pos, so the baby could be Rh-pos like the father. The Rh-pos cells will enter the mothers blood stream via the placenta and so the mother will naturally start to produce Rh-pos antibodies, these antibodies will then begin to circulate in the blood steam of the mother. As they circulate the antibodies for Rh-pos will pass through the placenta and into the baby which will cause the breakdown of the baby’s own erythrocytes and cause haemolytic disease
How can haemolytic disease be prevented
Detect anyone who could be at risk early
Anti-D Prophylaxis
Maternal feral free DNA
Who could be eligible for blood donation
Donors can be any gender and aged between 17 to 65
What screening questions do they ask before you are able to give blood
Body weight
Travel
Infections
Transmissible illnesses
Health
Medications
Medical history
Test for anemia
Who is temporarily excluded from donating blood
Travel within a certain timeframe to certain countries
Recent tattoos
Some lifestyle choices (sex with new partner)
Who is permanently excluded from donating blood
Having certain infectious diseases
What are the two ways blood/blood products can be donated
Whole blood
Apheresis
What is apheresis
When blood is taken, separated, the blood products taken with what is needed and the rest returned to the donor
Once blood is donated what mandatory tests are carried out on it
Hep B
HIV
Hep C
Syphilis
Blood group and antibodies present
Human T cell lymphotrophic virus
What other tests can be carried out on donated blood
CMV
Malaria
West Nile virus
Trypansoma
What happens to whole blood donations once it has been tested
Whole blood gets separated by been spun into red cells, buffy coat and plasma.
Plasma is only donated from males and once donated is frozen, this can be used to make cryoprecipitate.
Red cells are kept at an ambient temperature then passed through a filter and resuspended with additives.
The buffy coat is the pooled with donations and leucodplated to make platelets.
At what temperature can packed red cells be kept at and for how long for
Stored at 35 degrees
Kept for only 35 days
What is the transfusion threshold for packed red cells
Haemoglobin needs to be at <70g/dl or <80g/dl if symptomatic
What is the rule when transfusing packed red cells
Transfuse one unit then recheck full blood count/calcium before another transfusing
Why after transfusing 1 unit of packed red cells do you need to do a blood test on the patient
Packed red cells are suspended with 0.2% sodium citrate which can reduce the amount of calcium in the body. Calcium is needed in the clotting cascade and if low the patient could end up bleeding and then needing more blood than before
How do we get a donation of platelets
Platelet donation comes from the buffy coat of whole blood donations. The buffy coat is pooled from 4 different donations
What temperature at platelets are stored at and how long for
They are stored at 22 degrees
They are stored for 7 days
When platelets are stored what do they need
When platelets are stored they need continuous agitation
Why would someone need a platelet transfusion
Thrombocytopenia and bleeding
What is still important to consider when transfusing platelets
ABO blood types are still important due to antibodies still been present in plasma and could cause haemolytic reaction
How is safe delivery of blood managed
Check patient identification
2 samples taken from patient
Blood selected is serologically cross matched to check to reduce haemolytic reactions
What mistakes could be made during delivering a blood transfusion
Identification errors is the most common
Wrong blood been stored in the wrong tube
Laboratory errors are the least common
What causes haemolytic reactions and what doe it cause
This is due to serious ABO incompatibility
Which causes rapid intravascular heamolysis
Cytokine release
Acute renal failure
Intravascular coagulation
Can be fatal
How is haemolytic reaction treated
The transfusion should stop immediately
Fluid resuscitate
Does a haemolytic reaction happen immediately
No the reaction could be acute/immediately but it could be delayed
What are ways in which transfusion could be avoided
Use erythropoietin stimulating drugs (useful in renal failure)
IV iron for iron deficiency
Some people who present with low haemoglobin can tolerate it eg people with sickle cell
Transfusing what blood product can cause bacterial infection due to bacterial contamination.
How can the donation be checked
Platelets can be contaminated with bacteria
The donation can be check by inspecting the unit of platelets been used for transfusion
If the donation is an abnormal colour or cloudy this could indicate contamination
What are the symptoms of bacterial contamination from platelet transfusion
Fever
Hypotension
How is transfusion related lung injury caused
This is caused by AB antigens in the donor blood reacting with the recipients pulmonary endothelial neutrophils which causes the inflammatory cells to cause plasma to leak into the alveolar spaces
What are the symptoms of Transfusion related lung injury
Cough
Foamy sputum
Hypertension
Fever
