Blood Physiology Lec. 1 PDF

‫‪Lec. 1‬‬ ‫د‪.‬هناء عبد القادر‬  At the end of studying these lectures , the student is able to : 1- Understand the structure & functions of blood in health & disease. 2- Describe the formation of the formed element components of blood. 3- Explain the process of hemostasis. It is defined a...

‫‪Lec. 1‬‬ ‫د‪.‬هناء عبد القادر‬  At the end of studying these lectures , the student is able to : 1- Understand the structure & functions of blood in health & disease. 2- Describe the formation of the formed element components of blood. 3- Explain the process of hemostasis. It is defined as the scientific study of the structure & functions of blood in health & disease. It has been defined as a highly specialized tissue, which along with the circulatory system is adapted to meet the needs of the body tissues and organ systems. Such as exchange of gases, provision of nutrients, & removal of waste products. 1.Transportation:blood is the primary transport medium of the body. a. O2 enters the blood from the lungs & is carried to cells, & CO2 produced by cells is expelled. b. The blood from the (GIT) to cells transports ingested nutrients, electrolytes & water. 2.Maintenance: blood plays a crucial role in maintaining homeostasis(constancy of internal environment). a. Many of the hormones & enzymes are found in blood which act as buffers which help keep the blood’s PH within its normal limits of 7.35 – 7.45. b. Temperature regulation : because blood can hold heat, it is involved with temperature regulation. 3. Protection: a. Cells & chemicals of the blood constitute an important role in immune system , protecting against foreign substances such as microorganisms. b. Blood clotting also provides protection against excessive fluid & cell loss when blood vessels are damaged. The normal total circulating blood volume is 7% of the body weight. Blood is consisting of: 1- Plasma: the fluid portion of blood 55%. 2-Blood cells: the solid portion of blood 45%. Blood cells are: a. red blood cells (RBC’s) or erythrocytes. b. white blood cells (WBC’s) or leukocytes. c. cell fragments(platelets) or thrombocytes. The normal plasma volume is 55% of total blood volume Plasma remaining fluid only if an anticoagulant is added to the blood. If whole blood is allowed to clot and the clot is removed, the remaining fluid is called serum. Serum has essentially the same composition as plasma except that its clotting factors. Serum has essentially the same composition as plasma except that its clotting factors: fibrinogen (factor I), prothrombin (factor II), labile factor (factor V), and antihemophilic factor VIII have been removed. Plasma: is a pale yellow fluid that consists of: 1. 91% water: which acts as a solvent & suspending medium for blood component. 2. 2% other solutes such as ions , nutrients ,vitamins ,gases , regulatory substances (hormones), & waste products. 3. 7% plasma proteins: is a liquid containing suspended substance that does not settle out of solution. Most of the suspended substances are plasma proteins, which include albumin, globulins,& fibrinogen. Most of the plasma proteins are synthesized in the liver except circulation antibodies or immunoglobulin's (Ig's) which are manufactured in the plasma cells (from B- lymphocytes). Five major functions of plasma proteins: 1. Coagulation: fibrinogen is responsible for blood clots. If there is congenital absence of fibrinogen (a fibrogenemia) the result will be defect in clotting mechanism. There are plasma proteins known as fibrinolytic factors such as plasminogen, which prevent formation of spontaneous clots in the blood vessels. 2. Transport: many plasma proteins acts as carriers for many compounds involved in nutrition & hormonal integration. Albumin & globulins acts as carrier proteins. 3. Inflammation: Plasma also contains a number of proteins that play a major role in the production of inflammatory responses resulting from infection, allergy, or autoimmune disease. e.g. β- globulins. 4. Immunity: Immunoglobulin's (Ig's) or antibodies : Formed by β – lymphocytes & play a major role in the body’s defense against invading pathogens. Ig's are:, IgA, IgD, IgE, IgG ,& IgM. 5-Transvascular exchange of water: This is mainly the function of albumins. The osmotic (oncotic) pressure of albumins maintains the delicate balance between the two fluid compartments. About 60% of capillary oncotic pressure is due to plasma protein albumin, which is about 25 mmHg at arterial and venous ends of capillary and tends to cause osmosis of fluid inward through the capillary. Filtration is occurred at arterial end of capillary because capillary hydrostatic pressure, which is about 40 mmHg, exceeds the oncotic pressure, while at the venous end, reabsorption of water occurs because oncotic pressure exceeds capillary hydrostatic pressure, which is about 12 mmHg. If there is abnormal imbalance of forces at capillary wall, odema result. Odema : Is the failure of reabsorption of tissue fluids ( i.e. the filtration rate is exceed the reabsorption rate). Lymph is tissue fluid that enters the venous blood through lymphatic circulation. Composition: 1-It contains clotting factors. 2-It contains proteins that traverse capillary walls and return to blood via the lymph. The concentration of protein in the lymph is lower than that of plasma. Blood plays a) Minor role in maintaining homeostasis. b) crucial role in maintaining homeostasis. c) No role in homeostasis. d) Non of the above.