Blood Composition and Cell Types

Dr Dalia El Marakby Blood Definition: - It is a special type of connective tissue that circulate inside blood vessels. - Formed of cells and an extracellular matrix (plasma) Composition of blood:I- Plasma (55%) II- blood cells: (45%) a- Erythrocytes =Red blood corpuscles (RBCs). b- Leukocytes= (white blood cells) (WBCs). c- Platelets. Examination of blood: Blood film: *blood drop spread on a glass slide and left to dry. Staining: - with neutral stain as Leishman’s stain which is formed of: methylene blue (blue basic dye) + eosin (red acidic stain) + methyl alcohol (fixative). Red blood corpuscles (RBCs) (Erythrocytes) (erythro = red) - they are non-nucleated biconcave discs. *Shape: In top view rounded In side view Biconcave to increase surface area for gas exchange Abnormal Shapes of RBCs: Spherocytes: spherical Ovalocytes: Oval. Poikilocytes: pear shaped. Sickle cell: Crescent shape. -- Abnormal shape of RBCs may be due to change in the cell membrane or content of Hb. -- Abnormal shaped RBCs are more fragile, more liable to hemolysis causing anemia. 1 Dr Dalia El Marakby *size: Diameter is 6-9 µm with average 7.5 µm. Edge thicknesses 2.2 µm and central thickness 0.8 µm. Abnormal size: microcytic RBCs Less than (6 µm) macrocytic RBCs More than (9 µm) Anisocytosis different sizes * L.M.: -in unstained blood film, RBCs appear colored due to Hb - in stained blood film (Leishman’s stain) RBCs are rounded, non-nucleated, acidophilic (Hb is basic protein). -Pale central area (about 1/3 of the diameter) = normochromic *Rouleaux appearance: -RBCs may adhere to each other forming column (like column of coins). - Occur in slow circulation (not in normal circulation), reversible phenomena with no damage to cells. -Du to surface tension caused by their biconcave shape. N.B. these long chains of RBCs sediment more easily. This is the mechanism of increasing erythrocyte sedimentation rate (ESR), which increase nonspecifically with inflammation. * E.M.: *Glycocalyx contain antigens of blood groups (ABO, RH factor). *Cell membrane: flexible. *Cytoskeleton (spectrin, actin) keeps their shape and stability of the membrane *Hemoglobin (appear as electron dense homogenous). *No nucleus, no organelles * Life Span: - about 120 days. *Fate: - Old RBCs are phagocytosed by macrophages in liver, bone marrow & spleen. Iron is reused in formation of new RBCs &pigments are secreted as bile pigments. 2 Dr Dalia El Marakby * Osmotic fragility of RBCs: *RBCs maintain normal shape * Hemolysis * Crenation In isotonic solution = to OP of 0.9% saline. If RBCs are put in hypotonic solution They swell, burst, leak Hb, the remaining cell membrane is known as cell ghost. If RBCs are put in hypertonic solution, They shrink and show notches. *Count: counting either using: A- Hemocytometer B- Electronic counting instrument. Number of RBCs: average number 5 million/ mm3 in a normal adult male 5 - 5.5 million/mm3. in a normal adult female 4.5 - 5 million/ mm3 Due to stimulatory effect of male hormones on the bone marrow. RBCs count highest in newborns and gradually decrease. Abnormalities in number of RBCs: A-Anemia . Decrease number below 4 million / mm3 (oligocythemia) And Or decrease hemoglobin concentration. B- polycythemia. RBCs number above 6 million/ mm3 due to hypoxia that stimulate BM to produce more RBCs. It may be: physiological (high altitude, muscular exercise, new born). pathological (chronic heart& lung diseases). types of anemia: N.B. *Aplastic anemia: *Pernicious anemia *Sickle cell anemia: due to damage of the bone marrow leading to pancytopenia (decreased count of all blood elements) e.g. Irradiation, chemotherapy. (vit B 12 deficiency anemia) due to failed production of intrinsic factor by the stomach. formation of abnormal rigid type of Hb called (HbS) that accumulate at one side of the cell resulting in abnormal crescent-shaped RBCs (Sickle RBCs). 3 Dr Dalia El Marakby *Adaptation of RBCs to perform their function: Factor Mode of adaptation (I) plasmalemma 1- flexible allows squeezing inside narrow capillaries. 2-it is lipoprotein, which is highly selective to help gas exchange. (II) Shape 1- Biconcave Increases the surface area for gas exchange. 2- RBCs have rounded edges for easy passage in branched vessels. (III) Content 1-no nuclei or organelles, so: (33% Hb, -RBCs do not divide. –more space for Hb. 66% water, 1% enzymes) 2- Contain enzymes as Hb reductase (combine O2) & carbonic anhydrase (carry CO2). BLOOD PLATELETS Definition:- Small, oval cytoplasmic fragments. Origin: from megakaryocyte. Number: 200,000 - 400,000/mm3. Diameter: 2-4 µm. L.M. oval non nucleated fragments which have 2 zones: * Outer pale basophilic (clear) peripheral zone called = hyalomere. * Central dark granular zone = granulomere. E.M. and related function: 1-The cell membrane has a thick cell coat help platelet aggregation (platelet plug) to stop bleeding 2-Hyalomere contains: a- Cytoskeleton: *Microtubules to maintain the cell shape *Actin filaments (microfilaments) b- Membranous channels: *Open canalicular system: invaginations of the cell membrane *Dense tubular system: 3-Granulomere: a- Alpha (specific) granules b- Delta (dense) granules c- Lambda granules Help platelets to change their shape & clot retraction to release serotonin ……..vasoconstriction of the injured vessel Store for Ca. Contain clotting factors, growth factor & Ca. Contain serotonin, ATP& ADP. Lysosomes for clot removal after healing of the vessel. 4 Dr Dalia El Marakby d- Few mitochondria, ribosomes, glycogen (energy) Purpura = Thrombocytopenia: Decrease in number of platelets below 50,000 /mm3. It may be due to: 1- decrease production in the bone marrow (e.g. bone marrow depression). 2- increased breakdown (e.g. autoimmune diseases). It is characterized by prolonged bleeding time & excessive bleeding after minor trauma. White blood cells or Leucocytes General characters: see table Differences between the erythrocytes & leukocytes. Erythrocytes 1- Content 2- Types 3- Motility 4- Shape 5- Size Not true cell No Nuclei nor organelles One type Non motile Biconcave disc 6-9 (7.5 µm) 4.5 -5.5 millions/mm3 in males 4 -5 millions/mm3 in females 7-Osmotic pressure & fragility Easily hemolysed 8- Functions Gas exchange 6- Number White blood cells True cells with nuclei & organelles 5 Types Motile Spherical 6-20 µm 4,000 -11,000/mm3 Not easily hemolysed Defense 9- Origin and maturation bone marrow bone marrow& lymphoid tissue 10-Life span 120 days Days to years. Common characters of Granular Leucocytes: 1-life span: short life span (few days). Compensated from stem cells in bone marrow. 2-nucleus: a- single, segmented b- condensed with peripheral hetero chromatin with central euchromatin. 3- Cytoplasm: few organelles (mitochondria, rER &Golgi apparatus). it contains both nonspecific granules (azurophilic) & specific granules. * azurophilic: means have affinity for azure dye (oxidized methylene blue) according to the affinity of their specific granules to stain, they are classified into: 5 Dr Dalia El Marakby Granular leucocytes Life span % Diameter L.M. E.M. Neutrophils (polymorphonuclear, PMNs microphage) Few days 60- 70%. (Most common) 10-12 µm Nucleus: single, dark, segmented (2-5 segments connected with thin chromatin threads) thus neutrophils are called polymorphonuclear leucocytes (PMNs). Barr body seen in (3-6%) of ♀ cells. Cytoplasm: Specific granules: numerous, fine, pale granules. Azurophilic granules: few, large, purple with azure stain. - Nucleus: - peripheral hetero-chromatin and small central euchromatin. - Cytoplasm: -Have pseudopodia. -Few organelles few mitochondria, small GA, few rER. -Glycogen (energy) - Specific Azurophilic granules (2ry). granules (1ry) many few small larger pale dark. contain Contains *collagenase, myeloperoxidase, *lactoferrin. defensins proteins *Phagocytin. (against bacteria, *Lysozymes. viruses, fungi) Eosinophils Basophils Few days 1- 4% 10-14 µm Nucleus: horse- shoe (bilobed) connected with thick chromatin. Few days 0-1% (rarest) 10-12 µm Nucleus: irregular, segmented, pale and S- shaped. Cytoplasm: Specific granules: large retractile, acidophilic Cytoplasm: Specific granules: large (obscuring the nucleus), basophilic & metachromatically stained with toluidine blue giving purple color (due to heparin). - Nucleus: minimal peripheral heterochromatin & more central euchromatin. -Cytoplasm: - The cell membrane shows receptors for Ig E. -Few organelles. Specific Azurophilic granules granules Large, rounded Small electron dense lysozymes Contain *Histamine, *Heparin *Eosinophil chemotactic (ECF) factor - Nucleus: - peripheral heterochromatin & more central euchromatin than neutrophils. - Cytoplasm: -Few organelles. specific azurophilic granules granules oval with Small, electron dense lysosomes. core of basic protein (Internum) & less dense periphery (externum) Contain histaminases, 6 Dr Dalia El Marakby Functions -Neutrophils are first line of defense (nonspecific). Bacterial toxins attract neutrophils that leave the blood bypass between B.V. endothelium & go to the C.T. by process called diapedeses & become actively motile & have pseudopodia (microphages). In C.T. 1- Phagocytose bacteria: First the Specific granules release contents into phagosome & C.T. -Lactoferrin binds iron which is important for bacterial growth (bacteriostatic). -Phagocytin bactericidal (kill bacteria) (bactericidal). -Lysozyme destroys bacterial proteins, - Collagenase destroy collagen, so facilitate movement of neutrophils. Second the nonspecific granules release their enzymes Myeloperoxidase kill bacteria & other enzymes cause their lysis. 2- dead neutrophils form pus cells. sulphatase & eosinophilderived neurotoxin. 1- Termination of allergic reaction: a- Release histaminase & sulphatase to destroy histamine & heparin and end allergy. b-Phagocytose antigen antibody complexes. 2- defense against parasites: a- cytotoxic effect basic proteins of on parasites by forming pores in their bodies. b- Neurotoxins causes nervous system dysfunction in parasites. 3- Pus ↑↑body temperature (Pyrogens) stimulates the heat regulating center in the brain. 4-Neutrophils attract monocytes to site of infection to clean it. 5-stimulate bone marrow to form more neutrophils. 6- Neutrophils secrete trephone substances: help healing of wound. 7 *leukotrienes. Secrete: a- Histamine leads to vasodilatation →sudden ↓↓in blood pressure →anaphylaxis. b- Heparin prevents blood clotting & promotes allergy. c-Leukotrienes cause bronchospasm →bronchial asthma. d-Eosinophil chemotactic factor, that attracts eosinophil to the site of allergy. e-Limited phagocytic power. Dr Dalia El Marakby Neutrophilia: ⇈ percentage > 75% due to acute pyogenic infection (acute tonsillitis, acute appendicitis & abscess) Neutropenia: ⇊ percentage <60% due to: typhoid, T.B, viral infections as influenza. Eosophilia⇈ percentage of eosinophil > 5% -allergic diseases: e.g, bronchial asthma, urticaria & eczema. - Parasitic diseases: e.g. Bilharziasis. Eosinopenia ⇊ percentage <1% in treatment with cortisone (inhibit their release from bone marrow ) Basophilia ⇈ percentage of basophilis 1. Allergic diseases. 2. Parasitic diseases. 3. Viral infection (Chicken pox). 4. Liver cirrhosis. Comparison between basophils and mast cells: Basophils Mast cells 1-Life span 2- size 3-shape of the nucleus 4-phagocytosis 5-granules 6-surface receptors Few days Weeks to months 10-12 µm 20-30 µm segmented rounded slight no Metachromatic due histamine& heparin. Antibody Ig E Non granular leucocytes 1- Monocytes %: 3-8% Life span: 3 days in blood and 3 months in C.T. Diameter: 13-20 µm (largest leukocytes) A- Nucleus: B- Cytoplasm: L.M. large, eccentric, kidney shaped, pale with1 or 2 nucleoli. Non granular, non-clear pale basophilic cytoplasm. Has frosted glass appearance due to lysosomes (azurophilic granules). 8 - E.M. Euchromatic with clear nucleolus. Pseudopodia, lysosomes (1ry & 2ry), well developed Golgi, rER, mitochondria. Dr Dalia El Marakby Functions: highly phagocytic cell: 1- Remain in blood for 3 days. 2- Enter C.T. & change into macrophages to phagocytose bacteria and debris. 3- Antgin presenting cell. 4- Form all phagocytic cells e.g. dust cells of lung, osteoclasts of bone, kupffer cells of liver, microglia of CNS. Monocytosis: - ↑↑ number > 8% due to: -Chronic infection e.g. T.B., glandular fever, syphilis. -Monocytic leukemia. Monocytopenia: ↓↓ number. In pancytopenia. 9 Dr Dalia El Marakby II- Lymphocytes • 20-30% the most common type. • the 2nd line of the body defense. • They are "immune competent cells" as they have surface markers for antigens • Two types of lymphocytes according to activity: 2nd Small percentage Diameter: L.M. A- Nucleus: B- Cytoplasm: E.M. A- Nucleus: B- Cytoplasm: Large 15-20% of WBCs. 6-8 µm 5-10% 10-15 µm * Darkly filling the cell. * Little, rim around the nucleus, pale basophilic. * Large, indented nucleus pale with clear nucleolus. * Abundant and deep basophilic. * Heterochromatic. * Cytoplasm contains free ribosomes, two centrioles, small azurophilic granules *Euchromatic with prominent nucleolus. * More ribosomes, lysosome developed Golgi apparatus & more mitochondria. Large lymphocytes: may be either activated lymphocytes or natural killer (NK) cells Distribution & motility: -actively motile, continuously circulating between blood &lymphatic organs, where they settle. -They are the only leucocytes which can return to blood. -They are found in blood, lymph & lymphatic tissue. 10 Dr Dalia El Marakby Classification of lymphocytes - Have similar LM & EM. They differ only in surface receptors. -They divided into 3 types according to function: 1) T-Lymphocytes 2) B-lymphocytes % 60-80% of circulating 20-30% of circulating lymphocytes. lymphocytes. life span years. Few days to few months Maturation site Stem cells in bone marrow - develop in Bursa of fabricius in migrate to Thymus gland, birds. differentiate & acquire receptors - Bone marrow in mammals where (Thymic education). acquire receptors. Surface markers -T- cell receptors (TCRs) e.g. -Receptors for Ig M, Ig D. (receptors) CD4, CD8 proteins. Functions Cell mediated immunity Humoral immunity 3)Natural killer cells (NK) 5-10% of circulating lymphocytes. years. -develop from precursor of T and B cells. -they do not mature in thymus. -CD16 and others. -have neither B or T receptors 1-Innate early immunity (no Thelper cell stimulation). 2-similar to cytotoxic T- cell. 3-secretion of interferon (antiviral) T-lymphocytes Functions (types): 1-Cytotoxic CD8+ T cells: secrete perforins that produce pores in the membrane of virally infected, transplanted, or neoplastic cells killing them directly (cell mediated immunity). 2- Helper CD4+ T- cells: activate B cells during humoral immune response. 3- Regulatory (Suppressor )T- cells: a. maintains unresponsiveness to self-antigen. b. Suppress excessive immune responses. 4- Memory T-cells: rapid response on re-exposure to the same antigen (secondary immune response). B- Lymphocytes Functions: When exposed to specific antigen they become activated by T helper cells to: a. Plasmablasts, then plasma cells to produce antibodies (Humoral immunity). b. B -memory cells responsible for the rapid second immune response. 11 Dr Dalia El Marakby N.B. Human Immunodeficiency Virus that causes AIDS, destroys T helper cells & patient becomes susceptible to infections. Lymphocytosis: increased percentage of lymphocytes > 30% due to : -Physiological in children - chronic infection e.g. T.B. & whooping cough. – leukemia. Lymphocytopenia: decrease percentage of lymphocytes < 20% as in pancytopenia. 12 Dr Dalia El Marakby 13 Dr Dalia El Marakby - Reticulocyte: -9 µm -Its percentage in the peripheral blood does not exceed 1%. -Increased percentage more than 1% occurs in hemorrhage or destruction of RBCs. -Acidophilic but contains remnant of ribosomes & polysomes that form reticulum. - stained with supravital stain (brilliant cresyl blue). -Megakaryocyte: * Very large (mega) cell with a diameter of (50-70 µm). * Single multilobed dark nucleus & basophilic cytoplasm. * It extends pseudopodia (platelet ribbons) where platelets detach. * Invaginations of the cell membranes form demarcation channels that divide the cytoplasm into small parts or platelets. 14