Blood 1

What are the functions of blood?

Transport - blood gases, ions, metabolites, hormones and heat (for homeostasis). Defence - immune defence, haemostasis

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Outline the main components of blood (1)

Can be separated by centrifugation. Plasma (ECF - contains dissolved substances including gases, metabolites, ions proteins etc. Occupies 55% of volume). Cells (white cells for immune defence and platelets for haemostasis)

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Outline the main components of blood (2)

Red cells (for oxygen transport, occupies 45% of volume)

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Describe features of red blood cells (1)

Erythrocytes. Bi-concave shape (flexible). Diameter of 7 micrometres (move through narrow vessels). Full of Hb for O2 carriage (no nucleus, some enzymes/membrane transporters). Nucleus extruded before release of rbc into blood

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Describe features of red blood cells (2)

Normal count 4-6 x 10^12/L. Lifespan about 120 days then destroyed in spleen and liver (dysfunctional). Continuous production (0.8% total/day)

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Describe features of white blood cells (1)

Leucocytes. WBC normal range 4-11 x10^9/L. Leucopenia (low in number), leucocytosis (high in number). Main role in immune defence against - micro-organisms (bacteria, viruses, fungal infections) other foreign cells and molecule, remove dying tissue

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Describe features of white blood cells (2)

Three main kinds - granulocytes (non-specific/innate), monocytes (non-specific/innate), lymphocytes (specific immunity/acquired)

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Describe features of a blood smear

Blood smeared onto microscope slide, stained to show main cell types in the blood. Shows that only the WBC have nuclei. Able to recognise structures e.g. neutrophils, eosinophils

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Describe features of granulocytes (1)

Innate/unspecific IR. All have multi-lobe nucleus and granular cytoplasm, main type (40-70% of wbc) is the neutrophil. Short lived front line defence against micro-organisms (esp. bacteria)

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Describe features of granulocytes (2)

Role in inflammatory response to injury (destroy damaged tissue and release chemicals involved in inflammation). High motile, squeeze through endothelial layer, phagocytic, chemotaxis (follow gradient of e.g. cytokine, toxin to get to source)

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Describe features of granulocytes (3)

Number in circulation increase rapidly in response to infection. Main constituent of pus at sites of infection. Highly motile and phagocytic with granules (including lysosomes) containing a variety of enzymes and inflammatory mediators

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What are the two kind of granulocytes?

Eosinophils and basophils

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Describe features of eosinophils

Red stained granules. Functions poorly understood but are involved in defence against parasitic infections and in some allergic conditions, 1-6% of wbc

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Describe features of basophils

Blue stained granules which contain histamine and vasoactive mediators. Circulating precursors of tissue mast cells involved in some allergic/hypersensitivity responses, <1% of wbc

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Describe features of monocytes (1)

Largest of wbc, 2-10% of wbc, highly motile phagocytes, relatively long lifespan, specific functions, circulating precursors of tissue macrophages

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Describe features of monocytes (2)

Functions (as macrophage) in destruction of damaged tissue, release cytokines, assist specific immune response by acting as antigen presenters to lymphocytes

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How does antigen presenting work?

Macrophage takes up debris/pathogens, ingested/digested. Antigens move onto surface of APC (MHC II). APC presents antigen with the antigen fragment to T-cell. Specific T-lymphocyte binds to antigen. Activated T cell then divides to carry out response

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Describe features of lymphocytes (1)

Responsible for specific immune response to foreign cells and molecules. Characteristic round nucleus, relatively small diameter and pale, non-granular cytoplasm. Long lifespan. Functions - B-lymphocytes (antibody producers, memory cells)

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Describe features of lymphocytes (2)

T-lymphocytes - helper and suppressor (regulate the immune response), cytotoxic (kill some virus-infected and malignant cells). NK (natural killer) cells (kill viruses and tumour cells)

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B-lymphocytes can be converted into which types of cells?

Memory cells and plasma cells (produce antibodies)

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L-lymphocytes can be converted into which types of cells?

Cytotoxic killer T-lymphocytes (or to T-helper cells, suppressor cells which interact with B-lymphocytes, regulate immune system)

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Describe features of platelets (1)

Thrombocytes, 150-400 x 10^9/L. Tiny fragments of cells with sticky membranes. Important role in haemostasis (arrest of bleeding), aggregate to form temporary plus as immediate response to damage of vessel wall

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Describe features of platelets (2)

Plug promotes clot formation by acting as surface for assembly of clotting proteins, secrete factors involved in vascular repair

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How do motile cells escape from the blood into the tissues?

Neutrophils squeeze into endothelial layer to site of damage and inflammation (chemotaxis - cell moves along chemical gradient)

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Describe features of analysing cellular constituents of blood (1)

Haematocrit/packed cell volume, fraction/% of volume which is rbc, normal value about 0.45/45%, low values more common than high ones. Can reflect change in number of rbc and/or change in size of rbc

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Describe features of analysing cellular constituents of blood (2)

Hb content - grams of Hb per L of blood (normal value about 150 g/L). Hb is the O2 carrier (about 1.3 mLs O2 carried per g Hb). Reduction (caused by low number of rbc, small size of rbs, low Hb per rbc), results in anaemia and poor tissue oxygenation

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Describe features of analysing cellular constituents of blood (3)

Increase (caused by increased number of rbc, increase O2 carrying capacity compensates for low pO2 at high altitude/chronic lung diseases), some people inject themselves with blood (athletes)

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Describe features of analysing cellular constituents of blood (4)

RBC parameters - rbc count (number per L of blood, 4-6x 10^12/L), increased number (polycythaemia), reduced number (anaemia), from count and PCV, calculated mean rbc volume (~90 fL), microcyctic (low volume), macrocytic (high volume)

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Describe features of analysing cellular constituents of blood (5)

From count and [Hb] calculate mean rbc Hb content (~30 pg), hypochromic (low Hb content), from PCV and [Hb] calculate mean rbc Hb concentration (~30 g/dL)

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Describe features of analysing cellular constituents of blood (4)

WBC - total (number of wbc per L of blood, 4-11 x 10^9/L), differential (proportions of 5 different types)

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Outline features of blood groups (1)

Mixing blood samples from 2 different individuals often results in clumping (agglutination) of rbc, followed by their lysis (haemolysis). Underlying cause due to binding of plasma antibodies to antigens on rbc surface

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Outline features of blood groups (2)

Blood transfusions (cross matching required to ensure patients not transfused with incompatible blood) and organ transplantation/forensic science/anthropology etc

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Describe features of blood group antigens

Carbohydrate or protein group on the outside surface of rbc membrane. Genetically determined. More than 300 kinds, belonging to a small number of types (groups/systems) of which the most important in humans are: ABO system and Rh system

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What is the ABO system?

ABO system (carbohydrates) rbc may have A antigen (group A) or B, or both (AB) or neither (O)

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What is the Rh system?

Rh system (complex of proteins), rbc may have Rh complex (Rh positive ~85% population) or not (Rh negative)

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Describe features of blood group antibodies

Antibodies to the rbc antigens which the individual does not have. Ability to produce anti-A and anti-B antibodies, develops gradually over 1st year of life. Anti-Rh antibodies are produced only if Rh negative individual is exposed to Rh positive rbc

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Give an example of two people within the same organism with different blood groups?

Pregnancy

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What would happen if a person has antigen A?

They will produce antibodies for antigen B. If blood with antigen B was transfused into this person, agglutination will take place

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What would happen if a person has antigen B?

They will produce antibodies for antigen A. If blood with antigen A was transfused into this person, agglutination will take place

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Describe features of the ABO system (1)

Blood group O (genotype OO, no antigens on rbc, antibodies for anti-A and anti-B, compatible donor group is O). Blood group A (genotype OA, AA, A antigens on rbc, antibodies to anti-B, compatible donor groups are A,O)

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Describe features of the ABO system (2)

Blood group B (genotype OB, BB, antigen B on rbc, antibodies for anti-A compatible donor groups are, B,O). Blood group AB (genotype AB, antigens A,B, no antibodies, compatible donor groups are A, B, AB, O)

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Describe features of the ABO system (3)

Major cross-matching takes into account only the effect of the recipient's antibodies against the donor's rbc (sufficient in emergency)

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Describe features of the ABO system (4)

If volume of donor blood is relative large, effect of donor antibodies against recipient's remaining rbc then also has to be taken into account (minor cross-matching) and this reduces range of donors

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Describe features of the ABO system (5)

Blood also subjected to additional analysis for other blood groups to ensure the best possible match

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Describe features of the Rh system (1)

Two membrane proteins, RhD and RhCE. Most people 85% are RhD+ (have Rh antigen on rbc surface), others are RhD- without antigen

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Describe features of the Rh system (2)

Anti-D antibodies are made by RhD- individuals only in response to exposure to RhD+ rbc e.g. following repeated blood transfusions, following pregnancy with RhD+ foetus

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Describe features of the Rh system (3)

Haemolytic disease of foetus and newborn occurs in RhD+ infants born to previously sensitised RhD- mother (making anti-D antibodies)

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What happens if the mother is tested as Rh-? (1)

Mother offered injections of anti-D antibodies during pregnancy. Cannot reach foetal circulation to degree where they cause harm to the baby. But they will destroy foetal cells in maternal circulation (prevents sensitisation of mother)

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What happens if the mother is tested as Rh-? (2)

If mother is sensitised, the baby will be monitored and treated where necessary (if mother is Rh+ - no intervention). Antenatal screening offers Rh test to all women

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Blood 1

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