Blood Physiology PDF

Blood Department of Physiology Faculty of Veterinary Medicine Zagazig University  Functions of Blood 1. It supplies the tissues with oxygen, nutrients as; glucose, amino acids & fatty acids. 2. It removes the waste as carbon dioxide, urea & lactic acid from the tissues 3. It h...

Blood Department of Physiology Faculty of Veterinary Medicine Zagazig University  Functions of Blood 1. It supplies the tissues with oxygen, nutrients as; glucose, amino acids & fatty acids. 2. It removes the waste as carbon dioxide, urea & lactic acid from the tissues 3. It has immunological functions, including circulation of white blood cells & detection of foreign material by antibodies 4. It coagulates to stop bleeding, which is one part of the body's self-repair mechanism 5. It performs as messenger since it transports the hormones & the signaling of tissue damage 6. It plays important role in controlling the acid-base balance, water balance, and electrolytes balance 7. It regulates the core body temperature Blood pH - Normal blood pH is regulated to stay within the narrow range of 7.35 to 7.45. - Blood that has a pH below 7.35 results in acidosis (acidemia) - Blood that has pH above 7.45 results in alkalosis (alkalemia) Blood Composition 1. Plasma which makes up 55% of blood volume. 2. Cellular elements makes up 45% of blood volume: (a) Red blood corpuscles (RBCs) or Erythrocytes (b) White blood cells (WBCs) or Leukocytes (c) Platelets or Thrombocytes  Albumin is the most common protein in plasma. It represents of nearly two- thirds (60-80%) of total plasma proteins (4-5 g/dl). Functions 1. It maintains the osmotic balance between the blood and tissue fluids and called colloid osmotic pressure or oncotic pressure. 2. Transports thyroid hormones & other hormones, in particular, ones that are fat-soluble 3. Transports fatty acids ("free" fatty acids) to the liver 4. Transports unconjugated bilirubin 5. Transports many drugs as penicillin 6. Competitively binds calcium ions (Ca2+) 7. Buffers pH because amino acids contain two effective groups: acidic carboxyl group and basic amino group  Hypoalbuminemia It is the decrease in albumin concentration in blood below its normal levels. This condition results from: 1. Liver disease; cirrhosis of the liver is most common 2. Excess excretion by the kidneys 3. Excess loss in bowel 4. Loss of plasma in excessive burns Hyperalbuminemia It is the increase in albumin concentration in blood above its normal levels - This condition is a sign of severe or chronic dehydration. Hyperalbuminemia is also associated with high protein diets  Edema Edema is an abnormal accumulation of fluid in the interstitium The main common causes include: 1. Rise in hydrostatic pressure as occurs in cardiac failure. 2- Fall in osmotic pressure as in nephrotic syndrome & liver failure. has immune functions  One molecule of Hb contains 4 iron atoms & can carry 4 molecules of oxygen. The iron atom of the heme has a valence of +2 (Fe2+, ferrous)  Factors Affecting Erythropoiesis 1.Tissue Oxygenation and Role of Erythropoietin Erythropoietin is a protein hormone that controls erythropoiesis. Erythropoietin is produced in the liver (20%) & kidney (80%) in response to low oxygen levels. The conditions that decrease O2 levels (tension) are: − High altitude and its resulting alkalosis − Increased demand of O2 in athletes - Anemia − Cardiopulmonary diseases ( e.g, prolonged heart failure & chronic asthma. So, Removal of both kidneys or when kidney failure is present, that animal becomes anemic due to inability of kidneys to produce erythropoietin and the liver cannot compensate the decrease in erythropoietin  3. Hormones a) Hepcidin − It is a peptide hormone produced by the liver. - It play a role in regulation of hemoglobin production. − It controls iron absorption in the gastrointestinal tract & iron release from reticuloendothelial tissue to be incorporated into the heme group of Hb in erythrocytes d) Hematopoietic growth factors − Secreted by lymphocytes & macrophages to regulate the proliferation & differentiation of progenitor stem cells to produce RBCs.  4.Nutrition 1 Vitamin B12 & Folic acid − Both vitamin B12 & folic acid are required for RBCs maturation, because they are essential for the synthesis of DNA, so, lack of either of them cause abnormal DNA and cause erythroblast apoptosis, resulting in anemia. − Vitamin B12 is also called Extrinsic Factor, which needs the Intrinsic Factor from the gastric juice for its absorption from small intestine. So, in case of deficiency of the intrinsic factor due to gastric problems, vitamin B12 should be given parentrally.. 2 Proteins − Deficiency of any one of the "essential" amino acids would give rise to anemia because they are necessary for the formation of the proteineous part (globin) of hemoglobin. 3. Iron, Cobalt &Copper − Iron : an adequate supply of iron is essential for heme synthesis. - Cobalt - is a component of vitamin B12. Anemia, specifically pernicious anemia, is one of the obvious symptoms of a cobalt deficiency. - Cobalt also stimulates erythropoietin release from kidney - Copper: - Is an essential cofactor for oxidation-reduction reactions. - Copper enzymes regulate various physiologic pathways, as energy production, iron metabolism, connective tissue maturation & neurotransmission. - Copper is carried & transported by plasma protein ceruloplasmin. In Phagocytic Cells 1.The Hb molecule broken into globin & heme. The heme portion is broken into green pigment called bilviridin & iron. a) Globin is degraded into its amino acids & reutilized in the body b) Iron is either stored in the phagocytic cells in the form of Ferritin Or transferred to the plasma & combines with a plasma protein known as apotransferrin to become transferrin. This transferrin circulates to the bone marrow, where the iron is used for the synthesis of new hemoglobin. 2. The biliverdin pigment is converted into a yellow pigment called bilirubin (water insoluble). 3. Bilirubin leave the phagocyte & carried in plasma by albumin. So, free bilirubin is present in plasma as bilirubin-albumin complex In Liver Cells The bilirubin – albumin complex enters the liver ,where, the albumin is removed & the bilirubin is conjugated with glucuronic acid to form bilirubin gluccoronides which called "conjugated bilirubin", which is water soluble The conjugated bilirubin secreted into the bile in this form& enter the intestine. In the Intestine Bacteria within the large intestine reduce the conjugated bilirubin to urobilinogen. i. The most of urobilinogen or stercobilinogen is oxidized to urobilin or stercobilin & excreted with the feces. ii. Both urobilin & stercobilin are the pigments that give the feces its color Rupturing of RBCs & the release of (Hb) into plasma  Types of jaundice 1. Pre-hepatic jaundice – occurs before the bilirubin transported from the blood to the liver due to ( hemolysis) as in blood parasites infestation. 2. Intra-hepatic jaundice ( known as hepatocellular jaundice) : in conditions that affect the liver, such as liver cirrhosis. 3. Post-hepatic jaundice ( known as obstructive jaundice): due to gallstones or liver fluke parasites, which create blockage in the bile duct system (this prevents the bile and the bilirubin inside it) from draining out of the gallbladder and into the digestive system. As microorganisms in rumen can synthesize vitamin B12 1. Vascular spasm Vasoconstriction of injured vessel is due to the contraction of smooth muscle in the wall of the vessel under the effect of serotonin. This 'spasm' may reduce (not stop) blood flow and blood loss. 2. Formation of a platelet plug Platelets aggregate at the point where a vessel ruptures. This occurs due to exposure of collagen (a protein found in the connective tissue located just outside the blood vessel). Upon exposure to collagen, platelets release ADP & thromboxane. These substances cause the surfaces of platelets to become sticky , so platelets accumulate, a 'plug' forms. 3.Blood Coagulation (Blood Clotting)  Intrinsic pathway Extrinsic pathway Intrinsic pathway, all the factors required for coagulation are present in the circulation. Extrinsic pathway: initiated by a factor released from injured tissue, called tissue thromboplastin or tissue factor (factor III).  Fibrinolytic System Thrombin is the key protease enzyme of the coagulation system, plasmin is the major protease enzyme of the fibrinolytic system, acting to digest fibrin to fibrin degradation products. Plasminogen, the inactive zymogen form of plasmin, is synthesized in the liver Physiological regulation of fibrinolysis by: a) plasminogen activator inhibitors (PAIs) which inhibit the physiological plasminogen activators b) alpha 2 -antiplasmin inhibits plasmin 2. Antigen Presentation :  Another function of macrophages is to alert the immune system to microbial invasion. After ingesting a microbe, a macrophage presents an antigen.  The processed antigens are complexes with the MHC II proteins. This enables T cells to recognize antigens presented to them associated with the MHC proteins.  The MHC proteins ( Major histocompatibility complex) are glycoproteins present on the surface of tissue cells and serve as self markers that enable the individual’s immune system to distinguish its cells from foreign cells.  * MHC-I : present in all nucleated cells  * MHC-II: present in Macrophage , B cells  Activated NK cells release cytotoxic granules which destroy the altered cells.