Blood Physiology PDF

BLOOD PHYSIOLOGY Blood It is a vital fluid circulating within the Definition cardiovascular system volume : Functions around 5-6 liters in an Componen adult man ts pH :7.4 in arterial blood  FUNCTIONS OF THE BLOOD 1. Transport: O2 – CO2 – Nutrients– waste...

BLOOD PHYSIOLOGY Blood It is a vital fluid circulating within the Definition cardiovascular system volume : Functions around 5-6 liters in an Componen adult man ts pH :7.4 in arterial blood  FUNCTIONS OF THE BLOOD 1. Transport: O2 – CO2 – Nutrients– waste products and hormones 2. Homeostatic Keeps the composition of tissue fluid constant 3. Defensive function mediated by: – White Blood Cells – Antibodies (immunoglobulins) 4. Hemostatic: prevents blood loss by formation of a blood clot (stops bleeding) COMPOSITION OF BLOOD 1. Plasma 55%  Water 90 %  Inorganic substances ( Ions ) Na , Cl etc.  Organic substances: o Plasma proteins (Albumin, globulins, Fibrinogen) o others 2. Cells 45% Red Blood Corpuscles White Blood Cells Platelets The Plasma (55% of total blood volume) Composition of plasma: – 90% water – 10 % solids : (7.2 % plasma proteins, 1.9% other organic substances) 0.9% inorganic salts ; Na, HCO3) Total plasma proteins (7.2g/100ml) Types of plasma proteins: – Albumin (3.5-5 g/100ml ) Plasma – Globulins (2.5 g/100ml ) (3 types alpha ,beta and gamma) – Fibrinogen (0.4 g/100ml)  Plasma proteins Types Site of Functions Types of plasma synthesis Specific proteins: Albumin (3.5-5 All are Non g/100ml ) Globulins (2.5 synthesize specific g/100ml ) Fibrinogen (0.4 d by the g/100ml) Prothrombin (0.01 liver gm/100ml) except gamma globulins  Functions of Plasma Proteins 1-Production of an effective osmotic pressure: Albumin causes the colloidal osmotic pressure which is about 25 mmHg, they regulates the passage of water and diffusible solutes through the capillary wall. 2. Blood Viscosity: caused by fibrinogen mainly. It helps in maintaining peripheral resistance. 3. Buffering function: plasma proteins provide about 15% of the buffering capacity of the blood 4. Clotting of the blood: by fibrinogen, prothrombin and other clotting factors. 5. Defensive function: Gamma globulins are immunoglobulins 7. Act as carriers for some hormones, drugs, metal ions and other molecules and prevent their rapid loss in urine. Blood Cells Erythrocytes (RBCs) (4.5-5.5 million/mm3) Platelets (200,000-300,000/mm3) Leucocytes (WBCs) (4,000-10,000/mm3)  Functions of RBCs The RBCs are non nucleated (to empty space for hemoglobin) biconcave discs (to increase surface area and enhance flexibility) Functions: – Carry Hemoglobin which transports O2 and CO2 Counts: – In males 4.8-5.8 million/mm3 – In females 4.2-5.2 million/mm3 RBCs are also responsible for The red color of blood Determination of blood group by the antigens on their outer surface The viscosity of total blood  Hemoglobin Hb Oxh b It is a red pigment oxygen Hb inside the RBCs CarbaminoH b It contains 4 iron CO 2 atoms in ferrous form H b It transports CarboxyH b gases C O It is a powerful buffer Hb GlycosylatedH It is broken down b to bilirubin Glucos e Formation of RBCs Site of erythropoiesis Fetus : liver and spleen Children : bone marrow of all bones Adult : flat bones and ends of long bones Above 20 years : only flat bones ERYTHROPOIESIS Formation of RBCs Factors affecting erythropiosis: 1. Tissue oxygenation “ Erythropoietin” 2. Nutrional factors : – Proteins – Iron – Vitamins ( vit B12 , Folic acid ) 3. Hormones 4. Liver 5. Bone marrow  “ Erythropoietin” Erythropoiesis is controlled mainly by the hormone Erythropoietin. Erythropoietin is secreted from: 1. Kidney ( 90 % ) 2. Liver ( 10 % )  Secretion of erythropoietin is stimulated by Hypoxia Erythropoietin stimulates the bone marrow to produce RBCs.  “ Erythropoietin” Hypoxia  RBC - formation + Hypoxia stimulates kidney to secrete erythropoietin, which in turn stimulates bone marrow to produce more RBCs Erythropoietin + Classification of anemia morphologically ( according to blood indices) Normocytic normochromic Microcytic hypochromic Acute blood loss Macrocytic Hemolytic Iron deficiency anemia anemia Vitamin B12 or Aplastic anemia folic acid deficiency  ANEMIA Decrease in the number of RBCs &/or their content of Hb or both. Types of Anemia: A - Deficiency Anemia : 1 - Iron deficiency anemia : It is the commonest type of anemia. It is characterized by decreased Hb synthesis due to lack of iron. Causes: a - Chronic bleeding : e.g. Bilharziasis, gastric ulcer or piles. b - Heavy menstruation. 2 - Pernicious Anemia It occurs due to decreased absorption of vit. B12 B - Hemolytic anemia : It occurs due to excessive hemolysis (rupture of the RBCs). In hemolytic diseases the RBCs survival time is much reduced (about 20 day). Increase in RBCs destruction reduces the RBCs count and blood Hb level; the serum bilirubin is raised (jaundice). C - Aplastic Anemia : It occurs as a result of reduced bone marrow function and causes a decrease in levels of all blood elements.