blood &red blood cells. 2023pptx

Blood Mona A. Hussain Ass. Professor in Physiology FOM - PSU.

Objectives • State the normal shape, volume, and mean corpuscular hemoglobin of a normal RBC • Explain the factors regulating erythropoiesis • State the life span of normal RBCs, explain how and where they are destroyed. • Define anemia, and contrast its major types (hemolytic anemia, blood loss anemia, aplastic anemia, megalo-plastic anemia) as regards cause, shape, size, count of RBCs. • Describe the effects of anemia and polycythemia on the circulatory system..

Blood composition Blood is composed of cells and a liquid, called plasma, in which they are suspended. The cells are: – the erythrocytes (red blood cells), - the leukocytes (white blood cells), and – the platelets, which are not complete cells but cell fragments..

Plasma Composition • Water: 90% • Proteins: 7.1% • Other organic substances ( glucose, amino acids, lipids and waste products): 2% • Inorganic substances ( electrolytes; Sodium chloride, potassium, calcium,…..) less than 1% of plasma weight.

Plasma proteins • Proteins concentration: 6.5 – 8 g/ dl • Classified into: • 1- Albumin • 2- Globulins • 3- Fibrinogen • Site of synthesis: The liver Except gamma globulins by immune cells.

Functions of plasma proteins • Bind and transport other plasma constituents • PH puffer • Immunity ( gamma globulins) • Blood viscosity ( fibrinogen) • Blood clotting ( fibrinogens and other clotting factors • Osmotic pressure ( albumins) • Nutrients in starvation.

Circulating Blood Cell Levels TABLE 11.2 Blood Cell Type Erythrocytes (cells/pL) Men Women Leukocytes (cells/pL) Neutrophils Lymphocytes Monocytes Eosinophils Basophils Platelets (cells/pl-) Approximate Normal Range 4.3-5.9 x 106 3.5-5.5 x 106 4,500-11 ,OOO 100-1,000 0—500 0—100.

Red blood cells ( Erythrocytes) • Each microliter (a millionth of a liter) of blood contains 4 to 6 million erythrocytes • Production of erythrocytes in adult occurs in active bone marrow in flat bones and upper ends of long bones • Destruction: Red cells circulate for about 120 days after they are released from the marrow then they are destroyed in reticuloendothelial system Biconcave shape and their small size (7 µm in diameter) impart to the erythrocytes a high surface area-to- volume ratio. The erythrocyte plasma membrane contains specific polysaccharides and proteins that differ from person to person, and these confer upon the blood its type, or group..

Functions of erythrocytes • Transport of oxygen and carbon dioxide • Blood viscosity • Containing hemoglobin inside erythrocytes prevents the risks of free hemoglobin in plasma.

Production of Red Blood Cells • Early embryonic life Yolk sac • Middle trimester: LIVER + spleen + lymph nodes • Last month of gestation and after birth: exclusively in the bone marrow. (5 years, 20 years and > 20 years)..

Regulation of Red Blood Cell Production 90% Tissue Oxygenation Is the Most Essential Regulator of Red Blood Cell Production..

Effects of erythropoietin 1- stimulates the production of proerythroblasts 2- speeding up the production of new red blood cells..

Requirements of erythrocytes production • Nutritonal factors: Proteins, iron, vitamins ( B12 and folic acid) • Healthy bone marrow • Erythropoietin from kidneys and liver • Healthy liver • Hormones: androgens.

Life Span and Destruction of Red Blood Cells • 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 ATP. These enzymes also (1) maintain pliability of the cell membrane, (2) maintain membrane transport of ions, (3) keep the iron of the cells’ hemoglobin in the ferrous form rather than ferric form, and (4) prevent oxidation of the proteins in the red cells. • The metabolic systems of old red cells become progressively less active, and the cells become fragile, and the cell ruptures during passage through some tight spot of the circulation. (spleen 3 micrometer wide).

Anemia • Anemia is defined as a decrease in the ability of the blood to carry oxygen due to • (1) a decrease in the total number of erythrocytes, each having a normal quantity of hemoglobin, • (2) a diminished concentration of hemoglobin per erythrocyte, or • (3) a combination of both.

Table 12—10 Major Causes of Anemia l, Dietary deficiencies of iron (iron-deficiency anemia), vitamin BE, or folic acid 2. Bone marrow failure duc to toxic drugs or cancer 3. Blood loss from the body (hemorrhage) leading to iron deficiency 4. Inadequate secretion of erythropoietin in kidney discase 5. Excessive destruction oferythrocytes (e.g., sickle-cell ancnua).

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 red blood cell concentration usually returns to normal within 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.

Aplastic Anemia Bone marrow aplasia means lack of functioning bone marrow. Causes: • exposure to gamma ray radiation. • excessive x-ray treatment, • certain industrial chemicals, and • drugs.

Megaloblastic Anemia • Vitamin B12 and folic acid, are essential for RBCs maturation so that loss of any one of these can 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. Causes: • atrophy of the stomach mucosa, as occurs in pernicious anemia, • or loss of the entire stomach after surgical total gastrectomy • Red cells that are formed are mostly oversized, have bizarre shapes, and have fragile membranes..

Hemolytic Anemia • Different abnormalities of the red blood cells, many of which are hereditarily acquired, make the cells fragile, so that they rupture easily as they go through the capillaries, • Even though the number of red blood cells formed may be normal, or even much greater than normal in some hemolytic diseases, the life span of the fragile red cell is so short that the cells are destroyed faster than they can be formed, and serious anemia results..

Effects of Anemia on Function of the Circulatory System • In severe anemia, the blood viscosity may fall to as low as 1.5 times that of water rather than the normal value of about 3. • tis 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 as well as increased pumping workload on the heart. • 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, extreme tissue hypoxia results, and acute cardiac failure occurs.

Blood grouping: ABO system Blood group Antigen on erythrocytes Antibody in plasma A A Anti B B B Anti A AB A & B _________ O - Anti A & Anti B.

Rh system • People is divided according to Rh into: 1- Rh positive : 85% 2- Rh negative: 15% Rh group Rh antigens Anti Rh antibodies positive present absent Negative ( not sensitized) absent absent Negative ( sensitized ) absent present.

Importance of blood grouping • 1- Blood transfusion • 2- Medico-legal importance • 3- Pregnancy.

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