Blood Physiology Part I -cells

Composition of Blood • Consists of formed elements (cells) suspended & carried in plasma (fluid part) • Total blood volume is about 5L • Plasma is straw-colored liquid consisting of H20 & dissolved solutes – Includes ions, metabolites, hormones, antibodies 13­7

Physiology of Blood -Cells By Dr A. K. Gupta MD (Pediatrics) Ex . J.N. Medical College , A.M.U, Aligarh CMO (NFSG) ,Health Dept,GNCT of Delhi

Plasma Proteins • Constitute 7-9% of plasma • Three types of plasma proteins: albumins, globulins, & fibrinogen – Albumin accounts for 60-80% • Creates colloid osmotic pressure that draws H20 from interstitial fluid into capillaries to maintain blood volume & pressure

• Globulins carry lipids – Gamma globulins are antibodies

• Fibrinogen serves as clotting factor – Converted to fibrin – Serum is fluid left when blood clots 13­8

Red Blood Cells (Erythrocytes) The major function of red blood cells : Transport hemoglobin, which carries oxygen from the lungs to the tissues. Why Hb Should be inside RBCs: When Hb is free in the plasma, 3 % of Hb will leak through capillaries into tissue spaces or glomerular filtrate each time the blood passes through the capillaries. So, Hb must be inside red blood cells to remain in the human blood.

Red blood cells are responsible for most of the acid-base buffering power of whole blood? Explain 1.RBCs contain carbonic anhydrase enzyme which catalyzes the reversible reaction between carbon dioxide (CO2) and water to form carbonic acid (H2CO3). This reaction makes it possible for the water of the blood to transport CO2 in the form of bicarbonate ion (HCO3-) from the tissues to the lungs, where it is reconverted to CO2 and expelled into the atmosphere as a body waste product.

Shape and Size of Red Blood Cells. Biconcave discs Mean diameter -7.8 micrometers The average volume of the red blood cell is 90 to 95 cubic micrometers. The shapes of red blood cells can change as the cells squeeze through capillaries. Because the normal RBC has an excess of cell membrane for the quantity of material inside, deformation while passing through smallest cappilaries does not affect the membrane,so the Red Cells do not rupture passing through

Concentration of Red Blood Cells in the Blood. The average number of red blood cells is Men5,200,000 (±300,000) per cumm Women- 4,700,000 (±300,000) per cumm

Quantity of Haemoglobin in the Cells & amount of O2 carried. MAXIMUM CAPACITY : 34 Gm Hb in 100 ml of red cells. Men: Hb: 15 grams per 100 ml of cells; and Women: Hb: 14 grams per 100 ml. Each gram of pure haemoglobin carries 1.34 ml of oxygen. Therefore, in man 100 ml of blood can

HEMOPOIESIS: INTRO • Hemo: Referring to blood cells • Poiesis: “The development or production of” • The word Hemopoiesis refers to the production & development of all the blood cells: – Erythrocytes: Erythropoiesis – Leucocytes: Leucopoiesis – Thrombocytes: Thrombopoiesis.

Production of Red Blood Cells Body Areas of the Body That Produce Red Blood Cells. •In the early weeks of embryonic life- yolk sac. •During the middle trimester of gestation: liver (main), spleen and lymph nodes (additional sites). •Then, during the last month of gestation and after birth: exclusively in bone marrow.•Till 5 yrs age: The bone marrow of essentially all bones •5 – 20 years age- The marrow of the long bones, becomes fatty and produces no more red blood cells after about age 20 years.

Genesis of Blood Cells Pluripotential Hematopoietic Stem Cells, Growth Inducers, and Differentiation Inducers. The blood cells begin their lives in the bone marrow from pluripotential hematopoietic stem cell (PHSC). There are successive divisions of the pluripotential cells to form the different circulating blood cells. The intermediate-stage cells are very much like the pluripotential stem cells, but are committed to a particular line of cells and

CLONAL HYPOTHESIS PLURIPOTENT STEM CELL MULTIPLICATION

STEM CELL

COMMITTMENT

MULTIPLICATION COMMITTED STEM CELL

COMMITTED STEM CELL

PROGENITOR CELL CFU: COLONY FORMING UNIT

CFU A committed stem cell that produces erythrocytes is called a colony-forming unit-erythrocyte, and the abbreviation CFUE is used to designate this type of stem cell. Colony-Forming Units which form granulocytes and monocytes have the designation CFU-GM. Growth Inducers: Growth inducers are proteins that control the growth and multiplication of the different stem cells. Eg interleukin-3 , promotes growth and reproduction of all the different types of committed stem cells Differentiation Inducers Differentiation inducers are proteins which causes differentiation of one type of committed stem cell into a final adult blood

ERYTHROPOIESIS

FACTORS REGULATING ERYTHROPOIESIS • SINGLE MOST IMPORTANT REGULATOR: “TISSUE OXYGENATION” • BURST PROMOTING ACTIVITY • ERYTHROPOIETIN • IRON • VITAMINS: – Vitamin B12 – Folic Acid

• MISCELLANEOUS

ERYTHROPOIETIN • A hormone pro duced by the Kidne y. • A ci rc ul ati ng Gl yc oprote in • Now adays availa bl e a s Syn theti c Epoi eti n BY RE COMBI NANT TECHNOL OGY • Ac ts m ai nly o n CFU – E • Inc rea se s the number of : – Nucle ate d precur sor s in th e marr ow.

VITAMINS • B 12 : Cyanoc obal amine & F ol ic Ac id: – Is also cal led Ex tr insic F actor of Cast le . – Needs th e Intr insic Factor from th e Gastri c j ui ce for ab so rpti on from Smal l I nt est in e. – De ficiency cause s Pe rnicious (Wh en IF i s mi ssi ng) or Meg alo blasti c An emia . – Sti mul ate s Er yt hr opoie sis

IRON • Esse ntia l for the synthes is of Hemo glo bin. • Def icie ncy c ause s Mi croc yti c, Hypo chromi c Ane mi a. • The MCV ( ME AN CORP USCUL AR VOL UME -NORMAL 90) , Co lo r Inde x & MCH ( ME AN CORP USCUL AR HE MOGL OBIN) a re low .

ERYTHROPOIESIS: SEQUENTIAL CHANGES I PV R O N O R M O B L A S T

II VI E A R L Y N B L A S T

III I N T E R N B L A S T

MITOCHONDRIA BASOPHILIA HEMOGLOBIN

IV L A T E N B L A S T

R E T I C U L O C Y T E

M A T U R E R B C

ERYTHROID PROGENITOR CELLS • BF U-E : Bu rst Fo rming Unit – Erythroc yte : – Give rise eac h to th ousan ds of nuc leate d e ryth roid p re curso r cell s, in vi tr o. – Undergo some ch an ges to becom e th e Co lon y F or ming U nit sEr yth rocyt e (CFU -E ) – Regul ato r: Bur st Pr om ot ing Ac tivi ty (BPA )

ERYTHROID PROGENITOR CELLS • CFU- E: C olo ny Formi ng Uni tErythroc yte : – We ll d iff eren ti at ed eryt hroi d proge ni tor cell. – Pr ese nt on ly i n th e Re d Bon e Mar row . – Can form up to 64 nuc leate d eryt hr oid precur sor cell s. – Regul ato r: Er yth rop oi eti n.

• Bo th the se Pro ge nit or c ell s cannot be dist ing uis hed ex ce pt

Normoblastic Precursors • PROE RY THROB LAST (PRONORMOB LAST ): – Lar ge ce ll : 15 – 20 Microns in diam ete r. – Cy to plasm is dee p v iolet- blue stai ning – Has no H emo gl ob in. – Lar ge n ucle us 12 Mi crons o ccup ies 3/4 th of th e cell vol um e. – Nucle us has fi ne sti ppled re ticulu m & man y n ucle ol i.

Normoblastic Precursors • EARLY NORMOBLAST(BASOPHILIC ERYTHROBLAST):

– Smaller in size. – Shows active Mitosis. – No nucleoli in the nucleus. – Fine chromatin network with few condensation nodes found. – Hemoglobin begins to form. – Cytoplasm still Basophilic.

Normoblastic Precursors • INTERMEDIATE NORMOBLAST(REYTHROBLAST): – Has a diameter of 10 – 14 Microns. – Shows active Mitosis. – Increased Hemoglobin content in the cytoplasm – Cytoplasm is Polychromatophilic.

Normoblastic Precursors • LATE NORMOBLAST: – Diameter is 7 – 10 Microns. – Nucleus shrinks with condensed chromatin. – Appears like a “Cartwheel” – Cytoplasm has a Eosinophilic appearance.

Normoblastic Precursors • RETICULOCYTE:

– The penultimate stage cell. – Has a fine network of reticulum like a heavy wreath or as clumps of dots – This is the remnant of the basophilic cytoplasm, comprising RNA. – In the Neonates, Count is 2 – 6/Cu.mm. – Falls to <1 in the first week of life. – Reticulocytosis is the first change seen in patients treated with Vit B12

Normoblastic Precursors • MATURE ERYTHROCYTE: – Biconcave disc. – No nucleus. – About One-third filled with Hemoglobin.

Role of the Kidneys in Formation of Erythropoietin. 1. 90 per cent of all erythropoietin is formed in the kidneys; 10% in the liver. 2. in the kidneys the erythropoietin is formed probably in the renal tubular epithelial cells which secrete the erythropoietin, 3. when BOTH the kidneys are destroyed by renal disease, the person invariably becomes very anemic because erythropoietin formed

Effect of Erythropoietin in Erythrogenesis. •Stimulate the production of Proerythroblasts from hematopoietic stem cells in the bone marrow. •Speeds up Erythropoeisis by making proerythroblasts rapdly pass through different erythroblastic stages • The erythropoietin mechanism for controlling red blood cell production is a powerful one. •In the absence of erythropoietin, few red blood cells are formed by the bone marrow.

Maturation of Red Blood CellsRequirement for Vitamin B12 and Folic Acid •Vitamin B12 and folic acid are essential for the synthesis of DNA as they form thymidine tri-phosphate. Therefore, lack of either of them cause •Failure of rapid multiplication of erythroblastic cells. •Production of larger than normal red cells called macrocytes which are fragile and thus have a short life, one half to one third normal.

Pernicious Anemia. •In pernicious anemia there is red blood cell maturation failure due failure to absorb vitamin B12 from the gastrointestinal tract due to atrophic gastric mucosa. •The parietal cells of the gastric glands secrete a glycoprotein called intrinsic factor. •The Intrinsic factor binds tightly with the vitamin B12. In this bound state, the B12 is protected from digestion by the gastrointestinal secretions. •In the bound state, intrinsic factor binds to specific receptor sites on the brush border membranes of the mucosal cells in the ileum. •Then, vitamin B12 is transported into the blood during the next few hours by the process of pinocytosis, carrying intrinsic factor and the vitamin together through the membrane. • Lack of intrinsic factor, therefore, causes diminished bsorption of the vitaminB12. •Once vitamin B12 has been absorbed from the gastrointestinal tract, it is first stored in the liver, then released slowly as needed by the bone marrow. The minimum amount of vitamin B12 required each day to maintain normal red cell maturation

Failure of Maturation Caused by Deficiency of Folic Acid (Pteroylglutamic Acid). Folic acid is a normal constituent of green vegetables, some fruits, and meats (especially liver). It is easily destroyed during cooking. In small intestinal disease called sprue, there is highly reduced absorbption of both folic acid and vitamin B12

Formation of Hemoglobin •Synthesis of hemoglobin begins in the proerythroblasts and continues even into the reticulocyte stage of the red blood cells. When reticulocytes leave the bone marrow and pass into the blood stream, they continue to form minute quantities of hemoglobin for another day or so until they become mature erythrocytes.

Types of haemoglobins The different types of chains alpha chains, beta chains, gamma chains, and delta chains form diferent types of haemoglobins: 1.HbA: The most common form of hemoglobin in the adult human. It is a combination of two alpha chains and two beta chains. It has a molecular weight of 64,458. A total of four molecules of oxygen (or eight oxygen atoms) that can be transported by each hemoglobin

2. The types of hemoglobin chains in the hemoglobin molecule determine the binding affinity of the hemoglobin for oxygen. For instance, in sickle cell anemia, the amino acid valine is substituted for glutamic acid at one point in each of the two beta chains. When this type of hemoglobin is exposed to low oxygen, it forms elongated crystals inside the red blood cells which make it almost impossible for the cells to pass through small

Combination of Hemoglobin with Oxygen. 1. Oxygen binds loosely with one of the coordination bonds of the iron atom. This is an extremely loose bond, so that the combination is easily reversible. 2. Furthermore, the oxygen does not become ionic oxygen but is carried as molecular oxygen (composed of two oxygen atoms) to the tissues, where, because of the loose, readily reversible combination, it is released into the tissue fluids still in the form of molecular oxygen

Iron Metabolism Uses of Iron in body: 1.For the formation of hemoglobin 2. For formation of other elements like e.g., myoglobin, cytochromes, cytochrome oxidase, peroxidase, catalase The total quantity of iron in the body averages 4 to 5 grams, 1. 65 % in the form of hemoglobin. 2. 4 per cent is in the form of myoglobin, 3. 1 per cent is in the form of the various heme compounds that promote intracellular oxidation, 4. 0.1 per cent is combined with the protein transferrin in the blood plasma,

Daily Loss of Iron. 1. Excretion in faeces: 0.6 milligram per day, 2. Loss due to bleeding in woman due to menstrual loss :1.3 mg/day. Absorption of Iron from the Intestinal Tract Iron is absorbed from all parts of the small intestine, mostly by the following mechanism. •The liver secretes moderate amounts of apotransferrin into the bile, which flows through the bile duct into the duodenum. •In dudenum the apotransferrin binds with iron and withhemoglobin and myoglobin from meat. This combination is called transferrin. •Transferrin binds with receptors in the membranes of the intestinal epithelial cells. •Then, by pinocytosis, the transferrin molecule, carrying its iron store, is absorbed into the epithelial cells and released into the blood capillaries beneath these cells in the form of plasma transferrin. •Iron absorption from the intestines is very slow, only a

Regulation of Total Body Iron by Controlling Rate of Absorption. 2.When the body has become saturated with iron so that essentially all apoferritin in the iron storage areas is already combined with iron, the rate of additional iron absorption from the intestinal tract becomes greatly decreased. 3.On the contrary, when the iron stores have become depleted, the rate of absorption can increase five times normal. Thus, total body iron is regulated by altering the rate of absorption.

Life Span and Destruction of Red Blood Cells Body: When red blood cells are delivered from the bone marrow into the circulatory system, they normally circulate an average of 120 days before being destroyed. Even though mature red cells do not have a nucleus, mitochondria, or endoplasmic reticulum, they do have cytoplasmic enzymes that are capable of metabolizing glucose and forming small amounts of adenosine triphosphate. These enzymes also (5)maintain pliability of the cell membrane, (6)maintain membrane transport of ions, (7)keep the iron of the cells' hemoglobin in the ferrous form rather than ferric form, and (8)prevent oxidation of the proteins in the red cells. Once the red cell membrane becomes fragile many of the red cells self-destruct in the spleen, where they squeeze through the red pulp of the spleen. There, the spaces between the structural trabeculae of the red pulp, through which most of the cells must pass, are only 3 micrometers wide, in comparison with the 8-micrometer diameter of the red cell.

Destruction of Hemoglobin. •When red blood cells burst and release their hemoglobin, the hemoglobin is phagocytized almost immediately by macrophages in many parts of the body, but mainly Kupffer cells of the liver and macrophages of the spleen and bone marrow. •The macrophages release iron from the hemoglobin and pass it back into the blood, to be carried by transferrin either to the bone marrow for the production of new red blood cells or to the liver and other tissues for storage in the form of ferritin. •The porphyrin portion of the hemoglobin molecule is converted by the macrophages, through a series of stages, into the bile pigment bilirubin, which is released into the blood and later removed from the body by

Anemias Anemia means deficiency of hemoglobin in the blood, which can be caused by: •Blood Loss Anemia. •After rapid hemorrhage, the body replaces the fluid portion of the plasma in 1 to 3 days, but this leaves a low concentration of red blood cells. The Hb returns to normal by 3 to 6 weeks. •In chronic blood loss, a person frequently cannot absorb enough iron from the intestines to form hemoglobin as rapidly as it is lost. Red cells are then produced that are much smaller than normal and have too little hemoglobin inside them, giving rise to microcytic, hypochromic anemia, which is shown in Figure in next slide. 2. Aplastic Anemia. Bone marrow aplasia means lack of functioning bone marrow. For instance, a person exposed to gamma ray radiation from a nuclear

3. Megaloblastic Anemia. Deficiency of Vitamin B12, folic acid, and absence of intrinsic factor from the stomach mucosa lead to slow reproduction of erythroblasts in the bone marrow. As a result, the red cells grow too large, with odd shapes, and are called megaloblasts. Thus, atrophy of the stomach mucosa, as occurs in pernicious anemia, or loss of the entire stomach after surgical total gastrectomy can lead to megaloblastic anemia. Also, patients who have intestinal sprue, in

4. Hemolytic Anemia. Due to Breakdown of RBCs. Inherited defects of Red cell membrane make the cells fragile, so that they rupture easily as they go through the capillaries, especially through the spleen. The number of red blood cells formed may be normal in hemolytic diseases but the life span of the fragile red cell is so short that the cells are destroyed faster than they can be formed. Eg a. hereditary spherocytosis- the red cells are very small and spherical rather than being biconcave discs. These cells cannot withstand compression forces because they do not have the normal loose, baglike cell membrane

b. Sickle cell anemiaThe RBCs have an abnormal type of hemoglobin called hemoglobin S, containing faulty beta chains in the hemoglobin molecule, When this hemoglobin is exposed to low concentrations of oxygen, it precipitates into long crystals inside the red blood cell. These crystals elongate the cell and give it the appearance of a sickle rather than a biconcave disc. The precipitated hemoglobin also damages the cell membrane, so that the cells become highly fragile, leading to serious anemia. Such patients frequently experience a circle of events called a sickle cell disease “sicke cell crisis," in which low oxygen tension in the tissues causes sickling, which leads to ruptured red cells, which causes a further decrease in oxygen tension and still more sickling and red cell destruction. c. Erythroblastosis fetalis, Rh-positive red blood cells in the fetus are attacked by antibodies from an Rhnegative mother. These antibodies make the Rh-

Effects of Anemia on Function of the Circulatory System. •The blood viscosity falls. •This decreases the resistance to blood flow in the peripheral blood vessels, so that far greater than normal quantities of blood flow through the tissues and return to the heart, thereby greatly increasing cardiac output. •Moreover, hypoxia resulting from diminished transport of oxygen by the blood causes the peripheral tissue blood vessels to dilate, allowing a further increase in the return of blood to the heart and increasing the cardiac output to a still higher level-sometimes three to four times normal. •Thus, one of the major effects of anemia is

5. When a person with anemia begins to exercise, the heart is not capable of pumping much greater quantities of blood than it is already pumping. Consequently, during exercise, which greatly increases tissue demand for oxygen, extreme tissue hypoxia results, and acute cardiac failure ensues

Polycythemia Secondary Polycythemia (Production of large number of RBCs) It occurs when there is hypoxia in tissues because of too little oxygen in the breathed air, such as at high altitudes, or because of failure of oxygen delivery to the tissues, such as in cardiac failure, so the erythropoeitin stiumuate bloodforming organs to automatically produce large quantities of extra red blood cells. This condition is called secondary polycythemia, and the RBCs count rises to 6 - 7 million/mm3 ie 30 per cent above normal. Eg physiologic polycythemia, occurs in

Polycythemia Vera (Erythremia). In addition to those people who have physiologic polycythemia, others have a pathological condition known as polycythemia vera, in which the red blood cell count may be 7 to 8 million/mm3 and the hematocrit may be 60 to 70 per cent instead of the normal 40 to 45 per cent. Polycythemia vera is caused by a genetic aberration in the hemocytoblastic cells that produce the blood cells. The blast cells no longer stop producing red cells when too many cells are already present. This causes excess production of red blood cells in the same manner that a breast tumor causes excess production of a specific type of breast cell. It usually causes excess production of white blood cells and platelets as well. In polycythemia vera, not only does the hematocrit increase, but the total blood volume also increases, on some occasions to almost twice normal. As a result, the entire vascular system becomes

Effect of Polycythemia on Function of the Circulatory System •Because of the greatly increased viscosity of the blood in polycythemia, blood flow through the peripheral blood vessels is often very sluggish. •The color of the skin depends to a great extent on the quantity of blood in the skin subpapillary venous plexus. In polycythemia vera, the quantity of blood in this plexus is greatly increased. Further, because the blood passes slowly through the skin capillaries before entering the venous plexus, a larger than normal quantity of hemoglobin is deoxygenated. The blue color of all this deoxygenated hemoglobin masks the red

Leukocytes (White Blood Cells) The leukocytes, also called white blood cells, They are formed partially in the bone marrow (granulocytes and monocytes and a few lymphocytes) and partially in the lymph tissue (lymphocytes and plasma cells). After formation, they are transported in the blood to different parts of the body where they are needed in areas of serious infection and inflammation, thereby providing a rapid and potent defence

Genesis of leukocytes

Types of White Blood Cells. Six types of white blood cells are normally present in the blood. They are 1. Polymorphonuclear neutrophils, 2. Polymorphonuclear eosinophils, 3. Polymorphonuclear basophils, 4. Monocytes, 5. Lymphocytes, and, 6. occasionally, Plasma cells. The first three types of cells, the polymorphonuclear cells, all have a granular appearance, for which reason they are called granulocytes, or, in clinical terminology, "polys," because of the multiple nuclei. The granulocytes and monocytes protect the body against invading organisms mainly by ingesting them-that is, by phagocytosis.

Concentrations of the Different White Blood Cells in the Blood. Normal WBC count: Total Leukocyte Count (TLC) =7000 per ml of blood (in comparison with 5 million red blood cells). The normal % of the different types called Differential Leukocyte Count (DLC) is : Polymorphonuclear neutrophils 62.0% Polymorphonuclear eosinophils 2.3% Polymorphonuclear basophils 0.4% Monocytes 5.3% Lymphocytes 30.0%

INTRODUCTION • Leucocytes: Mobile units of the body’s defence mechanism • Formed in the : – Bone marrow – Lymphoid tissue.

• Rapidly deployed through the blood to areas where: – Infection & – Inflammation are seen.

CLASSIFICATION

OF

LEUCOCYTES

LEUCOCYTES 100

GRANULOCYTES

EOSINOPHILS 2.3

NEUTROPHILS 62

BASOPHILS 0.4

AGRANULOCYTES

MONOCYTES 5.3

LYMPHOCYTES 30

NEUTROPHILS • Most numerous Leucocytes ( 50 – 70%) • Are 10 – 14 Microns in diameter. • Have a constantly changing shape due to amoeboid movements. • The Nucleus can have 1 – 7 lobes connected by a fine strand. • The Cytoplasm contains 50 – 200 fine granules.

NEUTROPHILIA • NEUTROPHILIA: Increased neutrophil count, can be due to: – Release of stored cells from the bone marrow reserves. – Bacterial Infections causing increased Neutropoiesis. – Exercise can cause release of stored neutrophils.

Cytoplasmic Granules • Fine, azurophilic (Stain with both Eosin & Methylene blue) in nature. • Contain enzymes such as: – Cathepsins. – Phosphatases. – Nucleases. • Granules serve as lysosomes.

NEUTROPHILS & MONOCYTES: Functions

• They seek, attack and destroy invading bacteria, viruses and other injurious agents • Neutropils attack and destroy bacteria and viruses, even in the blood. • Monocytes are immature until they enter the tissues. There, they swell up to 80 Microns, develop lysosomes, and become Macrophages, capable of defence.

Neutrophils & Macrophages • Diapedesis: They squeeze through the pores of the blood vessels. • Amoeboid movement: They move at rates several times their own length! • Chemotaxis: Directed movement – cells move to wards infected areas.

EOSINOPHILS • 3 – 8% of the Leucocytes. • Have a typical ‘Spectacle shaped’, bilobed nucleus. • Have coarse bright pink staining granules in the cytoplasm.

EOSINOPHILS • They are parsiticidal in function. • Eosinophilia or increased count occurs in: – Parasitic infestations. – Allergic conditions. – TPE: Tropical Pulmonary Eosinophila.

Basophils • Are very few in number: < 1%. • Have a large indented nucleus which is obscured by cytoplasmic granules. • Granules are coarse and basic staining: blue. • They are abundant and protrude through the cell membrane.

LYMPHOCYTES: IMMUNOCYTES • Morphologically, – LARGE Lymphocytes: – Sized about 12 – 15 µ – Thin cytoplasmic rim – Large spherical nucleus – No cytoplasmic granules.

LYMPHOCYTES: IMMUNOCYTES Small Lymphocytes: – Sized about 8 µ. – ( Smallest Leucocytes) – Thin cytoplasmic rim & Large spherical nucleus. – No granules visible.

LYMPHOCYTES: IMMUNOCYTES

• Physiological Classification: T and B – ‘T’ LYMPHOCYTES : • Thymus trained or schooled cells • Responsible for Cell mediated immunity. • Provide protection against intracellular pathogens

LYMPHOCYTES: IMMUNOCYTES:

‘B’ LYMPHOCYTES – Trained in the Bone marrow(Bursa Fabricius in birds) – Responsible for Humoral Immunity.(Immunity through Antibody production) – Protect the body from encapsulated pyogenic bacteria like Pneumococcus & streptococci.

LEUCOCYTES: REVIEW • Chemotaxis: Directed movement • Chemotaxins: Cytotaxins & Cytotaxigens • Eosinophils: Spectacle shaped nucleus, Coarse pink granules. • Basophils: Coarse blue granules, obscuring nucleus. Custard apple appearance. • Lymphocytes: Physiologically T and B types.Responsible for immunity: Immunocytes.

Life Span of the White Blood Cells The life of the granulocytes after being released from the bone marrow is normally 4 to 8 hours circulating in the blood and another 4 to 5 days in tissues where they are needed. The monocytes : •Have a short transit time, 10 to 20 hours in the blood, before wandering through the capillary membranes into the tissues. •Once in the tissues, monocytes swell to larger sizes to become tissue macrophages, and, in this form, can live for months unless destroyed while performing phagocytic functions. •These tissue macrophages are the basis of the tissue macrophage system, which provides continuing defense against infection. Lymphocytes : 8.Enter the circulatory system continually, along with drainage of lymph from the lymph nodes and other lymphoid tissue. 9.After a few hours, they pass out of the blood back into the tissues by diapedesis. Then, still later, they re-enter the lymph and return to the blood again and again; thus, there is continual circulation of lymphocytes through the body. 10.The lymphocytes have life spans of weeks or months; this life span depends on the body's need for these cells.

3. Neutrophils and Macrophages Defend Against Infections It is mainly the neutrophils and tissue macrophages that attack and destroy invading bacteria, viruses, and other injurious agents. The neutrophils are mature cells that can attack and destroy bacteria even in the circulating blood.

How White Blood Cells Enter the Tissue Spaces: 1. By Diapedesis. Neutrophils and monocytes can squeeze through the pores of the blood capillaries by diapedesis. 2. by Ameboid Motion. Both neutrophils and macrophages can move through the tissues by ameboid motion. 3. Attracted to Inflamed Tissue by Chemotaxis. Many chemical substances in the tissues cause both neutrophils and macrophages to move toward the source of the chemical. This phenomenon is known

How White Blood Cells Enter the Tissue Spaces

Phagocytosis A. The most important function of the neutrophils and macrophages is phagocytosis, which means cellular ingestion of the offending agent. Phagocytes must be selective of the material that is phagocytized; otherwise, normal cells and structures of the body might be ingested. B. Whether phagocytosis will occur depends especially on three selective procedures.: •First most natural structures in the tissues have smooth surfaces, which resist phagocytosis. But if the surface is rough, the likelihood of phagocytosis is increased. •Second, most natural substances of the body have protective protein coats that repel the phagocytes. Conversely, most dead tissues and foreign particles have no protective coats, which makes them subject to phagocytosis. •Third, the immune system of the body develops antibodies against infectious agents such as bacteria. The antibodies then adhere to the bacterial membranes and thereby make the bacteria especially susceptible to phagocytosis. C. The Complement 3 molecules attach to receptors on the phagocyte membrane, thus initiating phagocytosis. This selection and

D. Mechanism of Phagocytosis by Neutrophils. 1.On approaching a particle to be phagocytized, the neutrophil first attaches itself to the particle and then projects pseudopodia in all directions around the particle. 2.The pseudopodia meet one another on the opposite side and fuse. This creates an enclosed chamber that contains the phagocytized particle. 3.Then the chamber invaginates to the inside of the cytoplasmic cavity and breaks away from the outer cell membrane to form a free-

E. Phagocytosis by Macrophages. •Macrophages are the end-stage product of monocytes that enter the tissues from the blood. •They are much more powerful phagocytes than neutrophils, often capable of phagocytizing as many as 100 bacteria. • They have the ability to engulf much larger particles, •Also, after digesting particles, macrophages can extrude the residual products and often survive and function for many more months. •Once Phagocytized, Most Particles Are Digested by Intracellular ENZYMES. Both neutrophils and macrophages contain an abundance of lysosomes filled with proteolytic enzymes especially geared for digesting bacteria and other foreign protein matter. The lysosomes of macrophages (but not of neutrophils) also contain large amounts of lipases, which digest the thick

F. Both Neutrophils and Macrophages Can Kill Bacteria. •In addition to the digestion of ingested bacteria,neutrophils and macrophages contain bactericidal agents that kill most bacteria even when the lysosomal enzymes fail to digest them. •Much of the killing effect is due to powerful oxidizing agents formed by enzymes in the membrane of the the peroxisome. These oxidizing agents include large quantities of superoxide (O2-),

Acute Increase in Number of Neutrophils in the Blood-"Neutrophilia." Also within a few hours after the onset of acute, severe inflammation, the number of neutrophils in the blood sometimes increases fourfold to fivefold-from a normal of 4000 to 5000 to 15,000 to 25,000 neutrophils per microliter. This is called neutrophilia, which means an increase in the number of neutrophils in the blood. Neutrophilia is caused by products of inflammation that enter the blood stream, are transported to the bone marrow, and there act on the stored neutrophils of the marrow to mobilize these into the circulating blood. This

Eosinophils The eosinophils normally constitute about 2 per cent of all the blood leukocytes. Eosinophils are weak phagocytes, and they exhibit chemotaxis, but in comparison with the neutrophils, it is doubtful that the eosinophils are significant in protecting against the usual types of infection. Eosinophils, however, are often produced in large numbers in people with parasitic infections, and they migrate in large numbers into tissues diseased by parasites. Although most parasites are too large to be phagocytized by eosinophils or any other phagocytic cells, eosinophils attach themselves to the parasites by way of special surface molecules and release substances that kill many of the parasites. For instance, one of the most widespread infections is schistosomiasis, Eosinophils attach themselves to the juvenile forms of the parasite and kill many of them. They do so in several ways: (1) by releasing hydrolytic enzymes from their granules, which are modified lysosomes; (2) probably by also releasing highly reactive forms of oxygen that are especially lethal to parasites; and (3) by releasing from the granules a highly larvacidal polypeptide called major basic protein.

Eosinophils also have a special propensity to collect in tissues in which allergic reactions occur, such as : 1.in the peribronchial tissues of the lungs in people with asthma and in the skin after allergic skin reactions. 2. The eosinophils are believed to detoxify some of the inflammation-inducing substances released by the mast cells and basophils and probably also to phagocytize and destroy allergen-antibody complexes, thus preventing excess spread of the local inflammatory process.

Basophils The basophils in the circulating blood are similar to the large tissue mast cells located immediately outside many of the capillaries in the body. Both mast cells and basophils liberate heparin into the blood, a substance that can prevent blood coagulation. The mast cells and basophils also release histamine, as well as smaller quantities of bradykinin and serotonin. I ndeed, it is mainly the mast cells in inflamed tissues that release these substances during inflammation. The mast cells and basophils play an exceedingly important role in some types of allergic reactions because the type of antibody that causes allergic reactions, the immunoglobulin E (IgE) type has a special propensity to become attached to mast cells and basophils. Then, when the specific antigen for the specific IgE antibody subsequently reacts with the antibody, the resulting attachment of antigen to antibody causes the mast cell or basophil to rupture and release exceedingly large quantities of histamine, bradykinin, serotonin, heparin, slow-reacting substance of anaphylaxis, and a number of lysosomal enzymes. These cause local vascular and tissue reactions that cause many, if not most, of the allergic manifestations.

Leukopenia (decreased WBC count) A clinical condition known as leukopenia occasionally occurs in which the bone marrow produces very few white blood cells, leaving the body unprotected against many bacteria and other agents that might invade the tissues. Causes : 4.Irradiation of the body by x-rays or gamma rays, or exposure to drugs and chemicals that contain benzene or anthracene nuclei, is likely to cause aplasia of the bone marrow. 5.Some common drugs, such as chloramphenicol (an antibiotic), thiouracil (used to treat thyrotoxicosis), and even

The Leukemias Uncontrolled production of white blood cells can be caused by cancerous mutation of a myelogenous or lymphogenous cell. This causes leukemia, which is usually characterized by greatly increased numbers of abnormal white blood cells in the circulating blood. Types of Leukemia. Leukemias are divided into two general types: •lymphocytic leukemias and 2. myelogenous leukemias. The lymphocytic leukemias are caused by cancerous production of lymphoid cells, usually beginning in a lymph node or other lymphocytic tissue and spreading to other areas of the body. The Myelogenous leukemia, begins by cancerous production of young myelogenous cells in the bone marrow and then spreads

Effects of Leukemia on the Body 2.The first effect of leukemia is metastatic growth of leukemic cells in abnormal areas of the body. •Leukemic cells from the bone marrow invade the surrounding bone, causing pain and a tendency for bones to fracture easily. •Almost all leukemias eventually spread to the spleen, lymph nodes, liver, and other vascular regions, regardless of whether the origin of the leukemia is in the bone marrow or the lymph nodes. •Common effects in leukemia are the

THROMBOCYTES: PLATELETS

Characteristics of Platelets 1. Diameter: Platelets are non nucleated minute discs of 1 to 4 micrometers diameter & donot multiply. 2. Formed in the bone marrow from fragmentation of Megakaryocytes under action of Thrombopoeitin formed in Liver. 3. The normal platelets count in the blood is between 150,000 and 300,000 per ml.

4. Active factors in Cytoplasm of platelets: • • •

• •

Contractile Proteins actin , myosin molecules, and thrombosthenin, which help platelets to contract; Endoplasmic reticulum and the Golgi apparatus that synthesize various enzymes and store calcium ions; Mitochondria capable of forming adenosine triphosphate (ATP) and adenosine diphosphate (ADP); ADP helps in aggregation of platelets. Fibrin-stabilizing factor-An important protein A growth factor that helps repair

5. The cell membrane of the platelets A glycoproteins coat which do not adhere to normal endothelium but adhere to injured areas of the vessel wall to the injured endothelial cells & or any exposed collagen from deep within the vessel wall. It contains phospholipids that activate multiple stages of the blood-clotting process. 6. Half-life of platelets in the blood is 8 to 12 days.

THROMBOCYTES: INTRO • Normally 1.5 - 4.0 Lakhs/Cu.mm in blood. • Are 2 – 4 µ in diameter; smallest blood cells. • Developed from giant cells called Megakaryocytes.

THROMBOCYTES: STRUCTURE • Spherical, oval, or rod-shaped colorless bodies. • Diameter is between 2 to 4 μ. • When unstimulated, under Electron Microscopy they appear as: – – – –

Flattened discs Having a cell membrane And a Cytoplasmic matrix. Microtubules encircle the thrombocyte just below it’s surface membrane.

THROMBOCYTES: STRUCTURE • • • •

Do not have nuclei. Cannot reproduce. But behave functionally as whole cells. Cytoplasm includes active proteins such as: –Actin. –Myosin. –Thrombesthenin.

THROMBOCYTES: STRUCTURE • Cell Organelles in thrombocytes include:

– Lysosomal granules. – Dense bodies: about 50 – 100 in number. – Mitochondria & Enzyme systems which produce: • ATP • ADP

– Enzyme systems producing:

• Prostaglandins – Local hormones.

THROMBOCYTES: Structures within – Fine Glycogen granules. – Microvesicles. – Microtubules. – Filaments. – Granules:

• Dense: Serotonin, ADP etc. • ά-granules: Clotting factors such as:

– Fibrin Stabilizing Factor (FSF) Factor XIII – PDGF: Platelet Derived Growth Factor

THROMBOCYTES: STRUCTURE • Internal Membranous systems: – Open Canalicular System: • Spongelike invaginations • Provide multiple channels for: – Taking up Calcium ions – Secreting granule contents.

– Dense Tubular System: • Channels of S.E.R. • Serves as an intracellular store for Calcium ions.

IDENTIFY THROMBOCYTES!

Platelet Physiology • Have a half life of 8 – 12 days. • Eliminated from circulation by the Tissue Macrophage system. • Thrombocytes are active structures.

• About half of them are removed by the Macrophages in the Spleen. • Platelet surface membrane has Phospho lipids, Cholesterol & glycolipids

THROMBOCYTES: FUNCTIONS • Formation of Platelet plugs in Hemostasis. – Activation. – Adhesion. – Aggregation/ Accumulation. – Cohesion or Plug formation

• Supporting Coagulatory mechanisms. • Phagocytosis. • Storage & transport of substances.

PLATELET PLUG FORMATION • It can by itself stop blood loss, if the rent is small. • Many such minute ruptures occur thousands of times every day in minute blood vessels. • Platelets manage to plug these very well, all by themselves.

APPLIED ASPECTS • Thrombocytopenia: – Decrease in Thrombocyte count.(Normal: 1.5 – 4 Lakhs/cu.mm of blood) – Critical Thrombocyte Count is 40,000/cu.mm. – Causes Purpura: • Multiple subcutaneous purplish blotches.

IDIOPATHIC THROMBOCYTOPENIC PURPURA – Usually cause not known. – Called as Idiopathic Thrombocytopenic Purpura. – Diagnosis by: • Easy bruisability & Purpura. • Critical Platelet count. • Prolonged Bleeding Time.

– Can be treated by giving multiple transfusions of: • Whole blood • Platelet rich plasma: PRP

APPLIED ASPECTS (Contd.) • With normal thrombocyte count, purpura may occur in • Thrombesthenic Purpura, where the thrombesthenin is defective. • Thrombocytosis can cause increased predisposition for Thrombotic events.

PURPURA