Department of Histology and Embryology, P. J. Šafárik University, Medical Faculty, Košice

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1 Department of Histology and Embryology, P. J. Šafárik University, Medical Faculty, Košice BLOOD: Syllabus for dental and general medicine students Author: doc. MVDr. Iveta Domoráková, PhD. BLOOD The blood vascular system is responsible for transport of: - oxygene, carbon dioxide - nutrients, metabolities, hormones and vitamins - regulation of body temperature, acid-base and osmotic balance Development: mesenchyme pluripotential hematopoietic stem cell Blood consists of two parts: - formed elements (blood cells- BC) - erythrocytes (red BC), leukocytes (white BC), platelets - plasma (the liquid in which are suspended blood cells) contains water, inorganic salts, proteins, amino acids, vitamins, hormones, lipoproteins Hematocrit: estimation of the volume of formed elements per unit volume of blood: 42-47% Volume: about 5,5 l in adult human body

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3 Hematocrit: estimation of the volume of erythrocytes per unit volume of blood. The normal value in the adult men is 40-50% and 35-45% in the adult women. If anticoagulants (heparin or citrate) are added to the glass tube with blood, than centrifuged, blood is separated into: lower, red coloured layer consists of erythrocytes (45% of entire volume of blood in the glass tube), thin layer immediately above, grayish in colour (buffy coat) consists of leukocytes and platelets (1% of the blood volume) and on the top is translucent, yellowish, viscous supernatant blood plasma (54%). Blood removed from circulatory system will clot. This clot contains formed elements and separated yelow liquid is called serum. 54% 1% 45% blood in the glass tube after centrifugation

4 RED BLOOD CELLS (Erythrocytes) Shape: - biconcave shape, without nuclei, life span: 120 days - never leave the circulatory system! Diameter: normocytes: 7,5 µm in diameter, 2,6 µm thick at the rim, 0,8 µm in the centre macrocytes grater than 9 µm microcytes smaller than 6 µm Anisocytosis presence of Ec with varying size

5 The normal concentration of Ec in blood - 5,5 milion / µl in men - 4,5-5,5 mil/µl in women Decreased concentration of Ec - anemia Increased number of Ec erythrocytosis or polycythemia Ec contain a 33% solution of hemoglobin, oxygen-carrying protein (basic protein, - acidophilia of Ec) Hemoglobin + oxygen = oxyhemoglobin Hemoglobin + carbon dioxide = carbaminohemoglobin Hemoglobin + carbon monoxide = carboxyhemoglobin - is irreversible! Mature Ec - no organells Younger Ec - reticulocytes (1% of the volume of circulating Ec) = immature stages of Ec released by the bone marrow into bloodstream, contain ribosomal RNA - basophilic granules.

6 PLASMALEMMA of erythrocytes: 40% lipid, 50 % protein and 10 % carbohydrate Specific peripheral membrane proteins are responsible for special shape and flexibility of Ec: fibrilar proteins spectrin and actin are bind to peripheral proteins with ankyrin and serves as membrane skeleton.

7 LEUKOCYTES (white blood cells) Number: /µl Leukocytes are classified to two groups: GRANULOCYTES (polymorphonuclear Lc) - segmented nucleus - 2 and more lobes - specific granules : neutrophilic, eosinophilic, basophilic - azurophilic granules (stained purple) are considered to be primary lysosomes contain: acid phosphatase, lysozyme, myeloperoxidase AGRANULOCYTES (mononuclear Lc) - no specific granules - presence of azurophilic granules - bind the azure dyes - nucleus round or kidney shaped Function: cellular and humoral defense of organism against foreign material (antigens - Ag) Leukocytes leave blood capillaries by diapedesis and enter the connective tissue!

8 1.GRANULOCYTES a / NEUTROPHILS: 60-70% Diameter µm 2 types of small granules, invisible in the LM Specific granules: membrane limited 0,3 µm, contain enzymes : alkaline phosphatase, collagenase, lactoferrin, lysozyme Azurophilic granules: primary lysosomes Nucleus: segmented 2-5 lobes (usually 3 lobes 41%) linked by chromatin bridges nonsegmented (band form) - the immature neutrophil Life span: 6-7 hours in blood, 1-4 days in connective tissue Function: phagocytosis of small particles (bacteria) neutrophils are called microphages

9 b / EOSINOPHILS: 2-4 % Diameter : µm Nucleus : bilobed, glass-shaped Specific granules - eosinophilic: 0,3 1,0 µm, (200 granules per cell) Granules contain enzymes: acidic phosphatase, hydrolytic enz., peroxidase, major basic protein Increased number of eosinophils is associated with allergic reactions and parasitic infection Function: eosinophils modulate inflammation by inactivation of the leukotriens and histamine, phagocytosis of Ag-Ab complex

10 c / BASOPHILS: less than 1 % Diameter : µm Nucleus : less heterochromatic, divided into irregular lobes, S-shaped or kidney shaped Basophilic specific granules: 0,5 µm, irregular in shape and size, stained basophilic or metachromatically Granules contain: heparin and histamine (similarity with mast cells) - production of leukotrienes - immediate hypersensitivity reaction

11 2. AGRANULOCYTES a / LYMPHOCYTES: 25-30% spherical shape Nucleus spherical with condensed chromatin (heterochromatin, dark basophilic nucleus) Cytoplasm - thin rim, slightly basophilic with azurophilic granules (lysosomes) Size: small 6-8 µm, medium µm, large 18 µm (activated by specific Ag) Life span: some live a few days, others for many years The site of lymphocyte development and differentiation into immunocompetent cells with specific integral membrane proteins: T lymphocytes develop in the thymus; Function: cellular imunity B - lymphocytes develop in the bone marrow; Function: humoral imunity (immunoglobulins)

12 T - LYMPHOCYTES: 80% of lymphocytes, very long life After activation by specific antigens (Ag) - proliferate and differentiate into effector cells: 1. helper T cells - positively regulate the activity T and B cells, produce lymphokines (MQ) 2. supressor T cells - inhibition of T and B cells, supress autoimmune diseases 3. cytotoxic cells / killer - secrete substances that kill tumor cells, viruses-infected cells and foreign grafts B - LYMPHOCYTES: 15% After activation by specific Ag differentiate into effector cells - plasma cells (Ig) NULL CELLS - 5% circulating stem cells that have neither T nor B lymphocyte surface antigens Immunologic memory - T and B lymphocytes after activation by specific Ag remain inactive - memory cells Upon subsequent exposure to the specific Ag - effector cells Detailed study of lymphocytes (types, function in lymphatic system Junqueira: Basic histology)

13 b / MONOCYTES: 3-8% of leukocytes Diameter: µm Nucleus: pale oval, horse-shoe or kidneyshaped Cytoplasm: basophilic with fine azurophilic granules (lysosomes) giving it blueish color Function: They represent precursors of the monocyto-macrophage system histiocytes, chondroclasts, osteoclasts, microglia in the nerve tissue, alveolar macrophages in the lung, Kupffer cells in the liver... After crossing of the capillary wall they enter to the connective tissue - differentiation into MACROPHAGES and Ag presenting cells

14 PLATELES (Thrombocytes) /µl Diameter 2-4 µm Life span: 10 days dark purple granulomere nonnucleated disc-like cell fragment originated from the fragmentation of megakaryocytes (bone marrow cells) LM + EM: LM: Peripheral hyalomere - light blue, pale basophilic EM: - open canalicular system, - marginal bundles of microtubules keep ovoid shape, - actin microfilaments - platelet movement and aggregation - Mitochondria LM: Central granulomere dark purple EM: - purple, azurophilic alpha granules - fibrinogen (visible in LM) - delta granules - Ca2+, ADP, ATP, pyrophosphate, serotonin (visible in EM like dense granules) - lambda granules - lysosomal enzymes Function: promote blood clotting help repair injury in the blood vessel walls

15 PLATELES (Thrombocytes) formation: - nonnucleated disc-like cell fragments, originated from the fragmentation of large cells - megakaryocytes that are present in the bone marrow - parts of megakaryocyte cytoplasm cross through the capillary endothelium, - fragments of cytoplasm cleave and become platelets flowing in the blood

16 Activated platelets change in shape to become more spherical, and pseudopods form on their surface. Thus they assume a stellate shape. platelets+ erythrocytes+fibrin

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18 Prenatal blood cell development 1. Mesoblastic period - in the wall of yolk sac; red blood cells develop from mesenchymal cells. 2. Hepato-lienal period - in the liver and spleen. 3. Medullary period starts in the bones, when bone marrow is created. Postnatal blood cell development Red bone marrow lies entirely within the spaces of bone, in the medullary cavity of young, long bones and the spaces of spongy bone (short bones, skull). Active hemopoiesis. Bone marrow consists of: 1. blood vessels, capillary sinusoids 2. supporting rericular cells, macrophages 3. small amount of adipocytes 4. hemopoietic tissue = developing blood cells arranged in cords development of blood cells occurs strictly in the bone marrow; matured cells cross the wall of capillary sinosoids and enter to the blood. Location of red bone marrow in adults (black) Yellow bone marrow innactive bone marrow, lies in the medullary cavities of the long bones of the arms, legs, fingers it is composed of adipocytes & reticular connective tissue, blood vessels hemopoiesis is stopped, but when necessary: e.g. severe loss of blood, it can revert to active red bone marrow Cavities in the spongy bone are filled with bone marrow

19 For development of erythrocytes are essential substances: hormone erythropoietin (produced in the kidney), iron, folic acid, vitamine B 12. Red blood cell maturation, a cell undergoes a series of differentiations (find why the cytoplasm change the staining accumulation of ribosomes (cytoplasm is basophilic), hemoglobin synthesis, releasing of the nucleus out of the cell). The following stages of development - within the bone marrow: 1. HEMOCYTOBLAST a multipotent hematopoietic stem cell 2. PROERYTHROBLAST 3. BASOPHILIC ERYTHROBLAST (early erythroblast; lot of ribosomes) 4. POLYCHROMATOPHILIC ERYTHROBLAST (late erythroblast; ribosomes + increase of hemoglobin) 5. ORTHOCHROMATIC ERYTHROBLAST (normoblast; high content of hemoglobin) + nucleus is expelled normoblast becomes a RETICULOCYTE (small amount of polyribosomes, which are lost soon). reticulocytes (1% )