Blood Physiology PDF

 Blood physiology  Blood Blood is a complex fluid that circulates continuously inside the cardiovascular system The function of the blood 1.Maintain the internal environment of the body constant  2. Maintenance of water balance: by removing excess fluids...

 Blood physiology  Blood Blood is a complex fluid that circulates continuously inside the cardiovascular system The function of the blood 1.Maintain the internal environment of the body constant  2. Maintenance of water balance: by removing excess fluids by the kidneys. 3.Maintenance of the arterial blood - pressure by its viscosity.  4. Hemostatic function : as it prevents bleeding from injured vessels.  5.white-blood cells provide the main defence mechanisms (phagocytosis) against microorganisms that cause disease.  Composition of the Blood: Cells Blood is composed of cells suspended in a clear yellowish fluid called the plasma. A. Cells: 1. Red blood cells 2. White blood cells 3. Platelets  Plasma 1. It is a clear yellowish fluid in which the blood cells are suspended. It is composed of water (90%) solutes(10% ). 1. Organic Substances : Plasma proteins ,waste products , nutrients, lipids, hormones and enzymes. 2. Inorganic Substances : Na+, K+, Ca++ ,Cl-, HCO3-, PO4  Plasma proteins 6-8gm% 7gm% Albumin Globulins Fibrinogen Prothrombin     Sites of formation of plasma proteins Plasma proteins generally are synthesized by the liver (albumin ,fibrinogen ,prothrombin &50%ofglobulins) gamma globulins are produced by The lymphoid tissues by plasma cells.  Albumin/ globulin ratio (A/G ratio) 1.2 It decrease in: 1- liver diseases (liver cirrhosis &hepatitis) it increase in decrease production of albumin 2- kidney increase increase Congenital albumin loss agammaglobuli 2-Infections nemia Increase production of immunoglobulins (y globulins functions of The plasma proteins 1. Respiratory function e.g. carriage of CO2 : CO2 combines with the amino groups of plasma proteins and carried as carbamino compounds. functions of The plasma proteins 2. Nutritional function: plasma proteins in prolonged starvation can be utilized for nutrition of the tissues. functions of The plasma proteins 3. Maintenance of the osmotic pressure of the blood ( 25mmHg) : which is essential for reabsorption of fluids from the tissue spaces at capillary venous ends which maintains the blood volume.Albumin is responsible for most osmotic pressure because of its greater amount and smaller molecular weight.  functions of The plasma proteins 4. Maintenance of acid base balance: and keeping pH of the blood constant by its buffer system.Plasma proteins are responsible for 15% of the buffering power of the blood as follows Lactic acid (strong) + Na proteinate Na lactate + proteinic acids (weak) functions of The plasma proteins 5. Maintenance of the arterial blood pressure: by sharing in production of blood viscosity which is important in production of peripheral resistance and maintenance of diastolic blood pressure. (fibrinogen) functions of The plasma proteins 6. Defence :against microorganisms and their toxins by gamma globulins(antibodies ). functions of The plasma proteins 7. Hemostatic function: due to the presence of fibrinogen and prothrombin which are essential for blood coagulation. functions of The plasma proteins 8. Transport and reservoir function: they act as transport proteins for substances circulating in blood e.g. hormones (e.g. thyroxine) and minerals (e.g. iron and copper). This provides a reservoir for these substances and prevents their loss in urine. functions of The plasma proteins 9. Control of the capillary permeability: plasma proteins close the pores in the capillary walls, thus limiting their permeability. Red Blood Cells  Erythrocytes are non-nucleated circular biconcave disks. Their Erythrocytes average diameter is 7.5 μm and thickness is 2 μm  Red Blood Cells Count:  In adult males: 5.4 million/mm3 (5.0-5.5 million/mm3 ).  In adult female: 4.8 million/mm3(4.5-5.0 million/mm3 ).  In newly born infants :6.0-8.0 million/mm3.  In children: 3.5-4.5 million/mm3.  Physiological Variations in Red Blood Cells Count: 1. Sex :It is higher in males than in females because 2. Age: RBCs count is high in newly born infants due to polycythemia. 3. Exercise, hot wheather and emotions :They increase RBCs count due to splenic contraction as a result of adrenalin secretion. 4. Diurnal variation: Changes in RBCs during the course of the day are usually slight, being highest in the evening and lowest during sleep. 5. High altitude:It raises the number of circulating red blood cells.  Structure of R.B.C’s They are not true cells because they do not have nuclei. Each RBC is formed of cytoplasm which is surrounded by a flexible semipermeable membrane.  Cell membrane 1. The red blood cell membrane consists of three basic components a. A lipid bilayer b. Transmembrane (integral) proteins c. Cytoskeleton : it is a protein network which is involved in the control of cell shape.  2. The cytoplasm contains: a)Hemoglobin which is the main constituent. Normal Values: - In adult males:14- 16 gm/100 ml. 10 - In adult female:12-14 gm/100 ml. b)Enzymes e.g. carbonic anhydrase (critical in CO2 transport) and glucose-6-phosphate dehydrogenase enzymes. c) Electrolytes e.g. K+ and HCO3 -.  Life Span and Fate of RBCs  1. Old RBCs are hemolyzed in the circulation and the spleen after 120 days. The released hemoglobin is engulfed by cells of the reticuloendothelial system where it is degraded into globin and heme.  2. Globin is re- used for Hb synthesis.  3. Heme molecule is separated into:  a. Fe2+ atoms which are stored as ferritin. Fe2+ atoms together with globin can be used for Hb synthesis.  b. The remaining part of heme is changed to biliverdin which is reduced to bilirubin. Bilirubin is released into the blood. In the liver , bilirubin is conjugated with glucuronic acid to form conjugated bilirubin which is secreted by the liver in bile.  Hemoglobin molecule Chromoprotein Globin Heme Four iron containing A protein made up of four nonprotein nitrogenous polypeptide (2  and 2 ) groups, each bound to chains one of the polypeptides