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Constituents of the Blood

Constituents of the Blood. Dr K K Hampton University of Sheffield. Blood has two phases. 1) Cellular component Red cells White cells Platelets 2) Fluid component Plasma. Blood. Cellular = 45% Plasma = 55% Haematocrit 0.45

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Constituents of the Blood

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  1. Constituents of the Blood Dr K K Hampton University of Sheffield

  2. Blood has two phases • 1) Cellular component Red cells White cells Platelets • 2) Fluid component Plasma

  3. Blood • Cellular = 45% • Plasma = 55% Haematocrit 0.45 • In anaemia cellular component decreasedacute anaemia = bleeding, also loose plasmahaematocrit 0.45, Hb low • chronic anaemia: only loose cells, plasma compensateshaematocrit 20%, Hb low

  4. Blood • In Polycythaemiacells > plasmahaematocrit > 50%Causes:

  5. Blood • In Polycythaemiacells > plasmahaematocrit > 50%Causes: Erythropoietin Hypoxia (leading to elevated Epo)

  6. Haematopoiesis(formation of the blood cells) • Red cells, white cells and platelets in circulation are mature cells, with finite life spanred cell = 120 days (make 2 million/sec)white cell = 6 hoursplatelet 7-10 daysred cells and platelets anucleate

  7. Haematopoiesis • Precursor cells of mature cells are in the bone marrowAdult = axial skeletonChild = all bonesIn utero = yolk sac, then liver and spleen • Precursor cells are not found in blood

  8. Haematopoiesis • Most primitive cells = stem cellsPluripotent: can replicate and differentiate into RBC, WBC and platelets(stem cells vital for marrow transplantation) • In bone marrow primitive cells proliferate and differentiate into mature cells

  9. Haematopoiesis • Hormonal growth factors stimulate cells to proliferate and differentiate • Epo = red cells • G-CSF = white cells • Tpo = platelets

  10. Red Cells • Simple cells, no nucleus, no mitochondria • Membrane to enclose Haemoglobin • Enzymes of glycolysis • Haemoglobin to carry oxygenHave a lot of them 4 X 1012/lHave 5 litres of blood

  11. Haemoglobin • Carries oxygen from lungs to tissues • Consists of protein, haem, ferrous 2+ ion • Allows oxygen to combine Reversibly with iron in an aqueous environment • Haemoglobin is a tetramer of 2 alpha and 2 beta chains

  12. White cells • Neutrophils • Monocytes (macrophages) • Basophils • Eosinophils • Lymphocytes

  13. Neutrophils • Phagocytose bacteria and foreign materialincreased in bacterial infections • Inflammatory cells, release pyrogens that increase temperature • Made in bone marrow from primitive cells called myeloblasts

  14. Lymphocytes • Immune cellsB cells (bone marrow) = 1 make antibodies 2 memory cellsT cells helper cells • Lack = immunodeficiencyHIV virus infects CD4 T cells • Make in bone marrow from lymphoblasts

  15. Platelets • Small cytoplasmic anucleate cells that block up holes in blood vessels • Determine the bleeding time • Circulate in inactive state • Bind to damaged blood vessel and adherechange shapedegranulateaggregate into platelet plug = haemostatic

  16. Platelets • Made in bone marrow from cells called megakaryocytesPolyploid cells, cytoplasm buds off to become platelets

  17. Platelet number • Normal = 140 – 400 X 109/l • Reduced = thrombocytopenia> 80 = increased bleeding> 20 = spontaneous bleeding • Increased = thrombocytosisArterial and venous thrombosis

  18. Plasma proteins • Soluble and in plasma component • Albumin • Carrier proteins for nutrients, hormones • Immunoglobulins • Coagulation proteins

  19. Albumin • Major protein in the plasma • Produced in liver • Determines oncotic pressure • Keeps intravascular fluid in that spaceLack of albumin results in oedemaLiver diseaseNephrotic syndrome

  20. Immunoglobulins • Produced by plasma cells = differentiated B lymphocytes • Several classes, IgG, IgM, IgA, IgE • Produced in response to non-self protein antigens • Production of antibodies basis of immunity and vaccination

  21. Coagulation proteins • Series of proteins (enzymes) that circulate in inactive form • Function is to make blood clot • Convert soluble fibrinogen into insoluble fibrin polymerOveractivity = thrombosisFailure = bleeding

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