Blood & Blood Formation

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Module IB Blood & Blood Formation Histology and Embryology Martin Špaček, MD (m.spacek@centrum.cz) http://www.lf3.cuni.

1 Module IB Blood & Blood Formation Histology and Embryology Martin Špaček, MD Approximately 7% of a person's weight is blood (about 5 L) Blood consists of the formed elements and plasma If blood is removed from the circulatory system, it will clot Serum: a yellow clear fluid lacking fibrinogen Blood clot: contains formed elements in a fibrin-containing network Blood collected in the presence of an anticoagulant (heparin or sodium citrate) and centrifuged Plasma Buffy coat: leukocytes and plateles Red blood cells: the hematocrit 40-50% in the men 35-45% in women Composition of Plasma Plasma is 92% water, about 1% ions and small soluble elements and 7% protein The main proteins: albumin globulins fibrinogen Formed Elements of Blood Red blood cells (erythrocytes) White blood cells (leukocytes) granulocytes agranulocytes Platelets (thrombocytes) 1

Studying Blood Cells: Preparation of the Blood Smear Spread a drop of blood in a thin layer on a slide Staining of Blood Cells After fixation, a polychromatic Romanowsky-type staining technique such

2 Studying Blood Cells: Preparation of the Blood Smear Spread a drop of blood in a thin layer on a slide Staining of Blood Cells After fixation, a polychromatic Romanowsky-type staining technique such as the Giemsa, Wright or Leishman method is used Four distinctive staining characteristic can be identified: basophilia (deep blue) azurophilia (purple) eosinophilia (pink) neutrophilia (salmon pink) Erythrocytes Biconcave disks Women average about 4.8 x 10 6 per µl Men average about 5.4 x 10 6 per µl Your body makes 2.5 million red blood cells every second 7.2 µm in diameter macrocytes diameter > 9 µm microcytes diameter < 6 µm Erythrocytes Erythrocytes Enucleated endpoint of a developmental series of nucleated precursors they are terminally differentiated live about 120 days No organelles Oxygen and carbon dioxide transport only function packed with hemoglobin Hemoglobin Consists of four polypeptides Each of these is attached the prosthetic group heme There is one atom of iron at the center of each heme One molecule of oxygen can bind to each heme 2

Sickle Cell Disease Inherited alteration in hemoglobin Caused by a mutation of one nucleotide in the DNA of the gene for the β chain Sickle Cell Disease When hemoglobin S is deoxygenated, it

3 Sickle Cell Disease Inherited alteration in hemoglobin Caused by a mutation of one nucleotide in the DNA of the gene for the β chain Sickle Cell Disease When hemoglobin S is deoxygenated, it polymerizes and forms rigid aggregates RBCs lose their normal elasticity Sickle Cell Disease Sickle cell disease results in several complications anemia pain infections stroke Sickle Cell Disease Survival advantage to heterozygotes in regions of endemic malaria Thrombocytes (Platelets) Cell fragments Smallest formed elements (2-4 µm in diameter) Responsible for initial clot formation Normal values: 150,000 to 400,000 per µl Thrombocytes (Platelets) Hyalomere peripheral transparent zone Granulomere central zone containing purple granules Open canalicular system 3

Granulocytes neutrophils eosinophils basophils Agranulocytes lymphocytes monocytes Leukocytes Multilobed nucleus (polymorphonuclear) Granules in cytoplasm lysosomes Most numerous of granulocytes

4 Granulocytes neutrophils eosinophils basophils Agranulocytes lymphocytes monocytes Leukocytes Multilobed nucleus (polymorphonuclear) Granules in cytoplasm lysosomes Most numerous of granulocytes (60-70%) Phagocytic (microphages) µm in diameter Neutrophiles Neutrophiles Eosinophiles Lobulated nuclei (typically bilobed) Large granules that attract eosin stain major basic protein 2-4% of leukocytes Diameter 12-15µm Role in allergic reactions and anti-parasitic functions Eosinophiles Basophils Rarest cells of blood less than 1% of leukocytes Diameter µm Nucleolus divided into lobes Large specific granules attract basic dyes heparin, histamine Function in immediate hypersensitivity reactions 4

Basophils Lymphocytes 20-30% of leukocytes diameter 6-18 µm almost no cytoplasm nucleolus is round, condense and inactive T cells and B cells are morphologically identical in the unstimulated or

5 Basophils Lymphocytes 20-30% of leukocytes diameter 6-18 µm almost no cytoplasm nucleolus is round, condense and inactive T cells and B cells are morphologically identical in the unstimulated or resting state Lymphocytes Lymphocytes Lymphocytes Activated B cells become plasma cells Activated T cells can become helper T cells or cytotoxic T cells Monocytes 3-8% of leukocytes Large cells (12-20 µm) Nucleolus is oval and eccentrically placed More cytoplasm than lymphocyte Monocytes leave the blood and become macrophages 5

6 Monocytes Differential Leukocytes Count Neutrophil Eosinophil Basophil Lymphocyte Monocyte 60-70% 2-4% 0.5-1% 20-30% 3-8% Changes in their relative number indicate some disorder Hematopoiesis Prenatal formation of blood cells: commences in the yolk sac later, the liver and spleen become dominant sites of hematopoiesis from the 5 th month occurs in bone marrow Hematopoiesis Total marrow space adult(70 kg) ml activeredmarrow: g Total marrow space child (15 kg) activeredmarrow: g Hemopoietic cells surround the vascular sinusoids and are supported by reticular connective tissue Red Bone Marrow Hematopoiesis All the various types of blood cells arise from a single type of cell called a pluripotential stem cell 6

Hematopoiesis Maturation of Erythrocytes Stem cells proliferate and develop into either lymhoid multipotential cells or myeloid multipotential cells Erythropoietin glycoprotein produced in the

7 Hematopoiesis Maturation of Erythrocytes Stem cells proliferate and develop into either lymhoid multipotential cells or myeloid multipotential cells Erythropoietin glycoprotein produced in the kidneys, enhances the production of RBCs Proerythroblast the first identifiable stage of erythropoiesis large, basophilic cell, which contains a large, lightly stained nulceus Maturation of Erythrocytes Basophilic erythroblast strongly basophilic cytoplasm large number of polyribosomes involved in the synthesis of hemoglobin Polychromatophilic erythroblas Orthochromatic erythroblast cytoplasm filled with hemoglobin The nucleolus is finally expelled The cell enters circulation as a reticulocyte, which still contains some organelles Origin of Platelets Fragmentation of the cytoplasm of megakaryocytes Megakaryocytes are very large cells (up to 160 µm) contain large, irregularly lobulated nuclei Maturation of Granulocytes Accumulation of nonspecific and specific granules Changes in nuclear morphology 7

8 Maturation of Monocytes Monoblast morphologically identical to the myeloblast Promonocyte large cell with basophilic cytoplasm Monocytes enter the bloodstream and then the connective tissues, where they mature into macrophages Maturation of Lymphocytes Although bone marrow is the ultimate source of lymphocytes, the lymphocytes that will become T cells migrate from the bone marrow to the thymus where they mature B cells develop from stem cells in the hemopoietic tissue Hematopoiesis is controlled by appropriate cytokines and hormones Interleukin-7 is the major cytokine in stimulating bone marrow stem cells to start down the path leading to the various lymphocytes. Erythropoietin, produced by the kidneys, enhances the production of red blood cells. Thrombopoietin, assisted by Interleukin-11, stimulates the production of megakaryocytes. Granulocyte-monocyte colony-stimulating factor (GM-CSF), as its name suggests, sends cells down the path leading to both those cell types. Under the influence of granulocyte colony-stimulating factor (G-CSF), they differentiate into neutrophils. Further stimulated by interleukin-5 they develop into eosinophils. Interleukin-3 participates in the differentiation of most of the white blood cells but plays a particularly prominent role in the formation of basophils. Stimulated by macrophage colony-stimulating factor (M-CSF) the granulocyte/macrophage progenitor cells differentiate into monocytes, the precursors of macrophages. 8

Cardiovascular System. Blood Components

Cardiovascular System. Blood Components Cardiovascular System Blood Components 1 Components of Blood Formed elements: erythrocytes, leukocytes, platelets Plasma: water, proteins, other solutes The components of blood can be divided into two