Blood Composition & Functions: PDF

‫سورة البقرة آية ‪32‬‬ Dr. Gehane Hamed Dr. Sherif Diaa 1) Describe the components of blood and their origins, and the role of hemoglobin in transporting oxygen in red blood cells. 2) Site of RBCs formation and factors affecting erythropoiesis.  Composition of the Blood Blood Comp...

‫سورة البقرة آية ‪32‬‬ Dr. Gehane Hamed Dr. Sherif Diaa 1) Describe the components of blood and their origins, and the role of hemoglobin in transporting oxygen in red blood cells. 2) Site of RBCs formation and factors affecting erythropoiesis.  Composition of the Blood Blood Composition: Blood consists of cells suspended in clear yellowish fluid called plasma The cells constitute 40 – 45% of the blood volume & the plasma constitutes 55 – 60% of the total blood volume. Hemopoiesis The cells include: Red blood cells (RBCs) or erythrocytes; there are about 5 million RBCs / mm³ White blood cells (WBCs) or Leukocytes; there are about 4000 – 11000 WBCs / mm³ Platelets or Thrombocytes; there are about 300.000 / mm³ General Functions Delivery of substances needed for cellular metabolism in the tissues Defense against invading microorganisms and injury Acid-base balance  Properties of the Blood: Color: Red due to hemoglobin & opaque due to its cellular elements PH: 7.4 in the arterial blood 7.36 in the venous blood Specific gravity: 1060 Viscosity: It is about 5 times that of water due to its cellular elements & plasma proteins. The plasma consists of: Water 90% Dissolved solutes 10%: 1-Organic substances:.Plasma proteins (7.1%) 2-Inorganic substances (2.9%): Includes electrolytes as; Na+, K+, Cl‾, HCO3‾, Ca²+ & PO4³‾(0.9%). Lipid, hormones, enzymes, nutrients & waste products (2%)  The Red Blood Cells (RBCs) Circular, non-nucleated, biconcave discs Survives in the circulation for an average of 120 days The average normal RBCs count = 5 million / mm³ in adult male & 4.8 million / mm³ in adult female They are manufactured in bone marrow They carry hemoglobin in the circulation.  Transport Hemoglobin Transport O2 and CO2 Acid Base Buffer Functions Erythrocytes  Physiological factors that affect red cell count: Age: - High in newly born infants - Low in old individuals Sex: higher in males because male hormones stimulate the erythrocytes Exercise, emotions & hot weather: due to spleen contraction High altitudes: hypoxia stimulates bone marrow Diurnal variation: - highest in the evening - Lowest during sleep.  Site of RBCs formation All blood cells develop from a common progenitor cell (stem cell) present in the bone marrow. The developmental process is called hematopoiesis. 100 billion cells are produced every day. In adults, the most active marrow is present in the vertebrae, sternum, and ribs. In children, the marrow is more active in the long bones.  Red Cell Life Span & Destruction In aged red cells, the metabolic activity in the cell decreases, & the cell membrane becomes more & more fragile. So, the aged cells rupture as they pass through tight places in the circulation (spleen). The destruction of red cells is facilitated by macrophages found in spleen, liver, bone marrow, & lymph nodes.  Hemoglobin (Hb) It is the red, oxygen-carrying pigment in the red blood cells Hb in normal adult human begins is called HbA, its amount average 15gm% (16gm% in males & 14gm% in females). Hemoglobin (Hb) Factors that affect erythropoiesis: Oxygen tension in blood: Hypoxia which is the O2 lack is the most powerful stimulus for erythropoiesis It indirectly acts through ↑ secretion of hormone erythropoietin from the kidney. Role of kidney: This organ secretes the erythropoietin hormone, Formed by the endothelial cells of the peri-tubular capillaries in the kidneys. It stimulates the red cell formation in bone marrow.. 85% of it secreted by kidney & 15% by liver.  Factors that affect erythropoiesis: Role of Liver: 15% of erythropoietin secretion. It forms the globin part of Hb Stores Vit. B12 & other minerals as iron. Role of Bone marrow: Hemopoiesis needs healthy bone marrow Its damage as by radiation or diseases → anemia. Hormones: Erythropoiesis is stimulated by →Androgen →Thyroxin. Diet: For normal erythropoiesis, the diet should contain: ▪ Protein of high biological value ▪ Vit. B12 & folic acid ▪ Minerals as copper & cobalt ▪ Iron