Veterinary Physiology 1 - Blood Lecture 1 PDF

LECTURE: BLOOD #1 Kavita R. Lall, B.Sc. (Hons.), D.V.M. (Hons.), M.Sc. (Dist.)  Learning objectives  Introduction  Erythrocytes  RBC metabolism  Fate of RBC  Abnormalities of RBC concentration  Understand what blood is, including its components  Discuss the different properties and...

LECTURE: BLOOD #1 Kavita R. Lall, B.Sc. (Hons.), D.V.M. (Hons.), M.Sc. (Dist.)  Learning objectives  Introduction  Erythrocytes  RBC metabolism  Fate of RBC  Abnormalities of RBC concentration  Understand what blood is, including its components  Discuss the different properties and functions of blood  Explain the commonly used method to determine blood’s specific gravity  Differentiate between plasma and serum  Discuss erythrocytes and how the shape differs in different species  Provide an overview of erythropoiesis  Describe the metabolism and fate of RBCs  Describe the two types of erythrocyte destruction  Appreciate the lifespan of erythrocytes in different species  Discuss abnormalities of RBC concentration  diet affects colour of urine horses have frothy urine  Blood: Fluid connective tissue that flows throughout the body in the blood vessels of the cardiovascular system it's a fluid connective tissue bc it connects different parts of the body  Plasma - fluid portion (55-70% TBV)  Water: 91-92%  Solids: 8-9% - proteins and organic and inorganic compounds Centrifusion of  Yellow to colourless depending on the quantity, species and animal’s diet blood  Suspended cellular elements (30-45% TBV) plama  Erythrocytes red blood cells  Leukocytes white blood cells buffy layer *  Thrombocytes platelets blood   Icterus index (plasma or serum) bilirubin comes from the breaking down of old blood cells  Estimates the total bilirubin concentration  It is measured by comparing the colour of the plasma with a standard solution of potassium dichromate 0 is normal...we want it to look normal the darker it gets, it means u might have liver, problems, or gaul stone u can determine what's wrong with the animal by doing this test  enzymes are dependent on pH potential of hydrogen  The normal pH of the blood is ~ 7.4  Dog: 7.32 - 7.68  Cattle: 7.35 - 7.50  Horse: 7.35 - 7.43 arteriole blood is oxygenated  Fowl: 7.56 deoxygenated blood  Venous blood: Slightly more acidic due to increased CO2  Acidosis and alkalosis very high rapidly fermented carbs, corn, wheat, barley, can cause ruminant acidosis  functions of blood: transportation homeostasis Functions of blood Transportation Regulation/maintain Protection homeostasis Oxygen and carbon pH/acid base balance Provides immunity dioxide Nutrients Body temperature Hormones Water balance Waste products Osmotic pressure  Specific gravity of blood  Specific gravity - the ratio of weight of a given volume of a fluid to the weight of the same volume of distilled water measured at 25°C more plasma proteins greater specific gravity  Plasma protein concentration is largely responsible for the specific gravity of the plasma higher amts of protein or cellular elements will cause higher specific gravity  The cellular elements have higher specific gravity than the plasma  Copper sulphate method: Commonly used manual method of hemoglobin determination based on specific gravity  When a drop of blood from a patient with normal hemoglobin values is dropped into a copper sulfate solution, it falls rapidly to the bottom; if the drop falls slowly or not at all, hemoglobin major protein levels are below reference range  Various factors influence the specific gravity of the blood  Specific gravity is increased: polycythemia - higher conc of red blood cells...causing specific gravity to be high  Polycythemia: High altitude, newborns  Severe dehydration: Excessive fluid loss such as in vomiting, diarrhoea specific gravity is higher in cases of severe cases of dehydration  Hemoconcentration: Loss of plasma, e.g. burns  Specific gravity is decreased:  Pregnancy: Increase in plasma volume (hemodilution)  Anaemia: Reduced RBCs  Renal diseases: Loss of albumin  Hemodilution: Hypersecretion or prolonged treatment with glucocorticoids  Starvation and malnutrition: Decrease in plasma protein  Intravenous fluid transfusions  Viscosity of blood  Viscosity is influenced by the concentration of RBCs and plasma proteins  Among plasma proteins, the viscosity is mainly contributed by immuno the gamma globulins which provide the resistance to blood flow and helps the normal pumping activity of the heart  It is normally about five times greater than water  Viscosity of blood is determined using a viscometer  An increase in the viscosity of blood is seen in conditions such as polycythemia, congestive heart failure, jaundice, vomiting, diarrhea lack of red of blood cells  A decrease in the viscosity is commonly noticed in anemia, oedema accumulation of fluid in tissues  Serum is plasma without the clotting factors plasma is the fluid part of the blood  Fluid that remains from plasma after clotting factors have been removed by clot formation  It differs from the plasma in lacking fibrinogen, prothrombin and other coagulation factors which are involved in blood coagulation  Erythrocyte  60-70% water  ~35% solids (of which 95% is contributed by Hb and 5% by stromal protein, lipids, phospholipids, cholesterol, vitamins)  allows red blood cells to tranfer  RBCs contain large quantities of carbonic anhydrase; thus transports large quantities of carbon dioxide from the tissues to the lungs in the form of bicarbonate  Hemoglobin is an excellent acid base buffer, therefore, the RBCs are responsible for most of the acid base buffering power of whole blood CO2 + H2O reversed arrow H2CO3 reversed arrow HCO3 + H+  Mammalian RBCs are usually non-nucleated, biconcave, circular discs with a central pale spot  Shape differs in various species  Dog, Cow, Sheep: Markedly biconcave  Horse and cat: Shallow concaving  Goat:Very shallow or flat surfaced erythrocytes  Camel: Elliptical  Deer: Sickle-shaped  Amphibians and birds: Elliptical and nucleated they retain their nucleus and it doesn't affect their o2 carrying abilities  Normal avian RBCs Normal canine RBCs Normal feline RBCs Normal deer RBCs Normal human RBCs Normal camel RBCs Normal goat RBCs  Average diameter of RBC: 4.1-7.5 µm  Surface area varies from 57-67m2/kg body weight in mammals; lowest in goat (smaller diameter) and highest in man (greater diameter)  Concentration of RBCs depends on various factors such as interspecies, intraspecies, age, sex, environment, exercise, nutritional status, climate and altitude  Erythropoiesis  Hematopoiesis: The processes of formation of erythrocytes (erythropoiesis), leukocytes (leukopoiesis) and platelets in the body  From stem cell, the formation of reticulocyte takes about 72 hours and conversion of reticulocyte to erythrocyte requires 48 hours; thus RBC formation requires 5 days  Under appropriate stimulation, CFU-E progenitor cells produce proerythroblast  Hb synthesis begins in polychromatophil erythroblast and maximum synthesis occurs in orthochromatic erythroblast  mature RC immature RC  BC- BLOOD CELL RBC RED BLOOD CELLS less o2 in tissue, hypoxemia is less o2 in blood  Hypoxia is the principle regulatory factor of erythropoietic activity of the bone marrow  Kidney produces 90% of erythropoietin and liver produces about 10%  Erythropoietin stimulates hemopoietic stem cells of bone marrow to produce the committed stem cells - proerythroblast  Vitamin B12 and folic acid are essential for the maturation of erythrocytes  Vitamin B12 is required for DNA synthesis  Folic acid is required for RNA synthesis necessary for pregnancy in organisms  Macrocytic anemia is common in Vitamin B12 and folic acid deficiencies  Thiamine (B1), Pantothenic acid, Nicotinic acid, Vitamin E and pyridoxine (B6), riboflavin, biotin and ascorbic acid are essential for erythropoiesis smaller  Deficiency of Vitamin B6 causes microcytic hypochromic anaemia in pigs  Normocytic anemia in swine and primates is due to Vitamin E deficiency less red in colour  Minerals are essential for erythropoiesis  Iron acts as an integral part of Hb which is essential for Hb synthesis  Copper acts as a co-factor in Hb synthesis  Copper deficiency is common in pigs, which may interfere with iron absorption and utilization  In ruminants, cobalt plays a key role for the synthesis of Vitamin B12 by the rumen bacteria  A low percentage (1-3%) of erythrocytes in circulation has a network of bluish threads within the cell and is called reticulocytes if more something is wrong since they dont fucntion like mature RC  These cells are immature RBCs, which have entered into the circulation at times of need  In some diseases or due to excessive loss of blood or destruction of RBCs, the reticulocyte number increases in circulation  These cells have less or no O2 carrying capacity  Energy is required for RBCs to:  Maintain the shape and flexibility of the cell membrane  Preserve high K+, low Na+ and low Ca2+ ions within the RBCs against the concentration gradient of these ions of plasma  Maintain iron in ferrous (Fe2+) state  Generate reduced glutathione (anti-oxidant); this helps to maintain the Fe2+ state  Generate 2,3-diphosphoglycerate (DPG) for O2 dissociation  Mitochondria is absent in mature erythrocytes they get energy differently since they don't have mitochondrion  Thus, they derive their energy from glucose metabolism via anaerobic Embden-Meyerhof (EM) pathway (90%) and oxidative pentose cycle (10%) which produce NADH and NADPH  Kreb's cycle is very much reduced in activity! major pathway by which RBC gel energy they use this one as well  Erythrocytes can change their shape when they pass through the capillaries but they become less flexible when they reach the end of their life span  In most domestic animals, the bone marrow functions as a chief site of erythrocyte destruction, whereas in man it is the spleen and in birds it is the liver  Two types of erythrocyte destruction takes place 1. Intravascular hemolysis minor pathway where they are destroyed 2. Extravascular hemolysis major way it is destroyed  Intravascular hemolysis  ~10% of aged RBCs undergo intravascular hemolysis within the capillaries due to loss of compressibility of RBCs caused by increased membrane permeability and osmotic change  When this occurs the hemoglobin is released, which combines with haptoglobulin, which is removed by the cells of the mononuclear phagocytic system (MPS)  Extravascular hemolysis  ~90%of the aged RBCs are directly destroyed by the mononuclear phagocytic system (MPS) macrophages and monocytes are found in liver and spleen  The Hb and proteins are catabolized by the MPS cells; MPS (also known as reticulo-endothelial system) includes the histiocyte or macrophages, stellate or Kupffer cells of the sinu- soids of the liver, spleen, mononuclear cells of bone marrow and lymph nodes  The globin of the Hb is degraded into amino acids and is reutilized in the formation of new hemoglobin or other proteins  Iron removed from the heme is stored in the MPS cells in the form of ferritin or hemosiderin and utilised for the synthesis of hemoglobin or enters the plasma and combine with apotransferrin to form transferrin which enters the bone marrow to produce more erythrocytes  Heme is converted into bile pigments, biliverdin (green pigment), and then reduced to bilirubin (yellow pigment)  Free bilirubin enters the plasma, binds with albumin and is transported to the liver, where it is conjugated with glucuronic acid  secreted in bile  Large intestinal bacteria reduce the bilirubin to urobilinogen, most of which are excreted in faeces in the oxidised form of urobilin or stercobilin which impart colour to faeces  Part of the urobilinogen is reabsorbed into the enterohepatic circulation and re-excreted in bile  Some of the urobilinogen in the plasma enters the kidneys to be excreted in urine as urobilin  Hemolysis caused by external agents:  Blood parasites: Babesia, theileria, trypanosoma and sarcocystis tick fever carried by ticks causing red blood cells to rupture  Chemicals: Copper, lead, nitrate and nitrite poisoning Life span of erythrocytes Species Life span (days) Cattle 125-150 Sheep 140-150 Goat 125-150 Horse 140-150 Dog 100-120 Cat 70-80 Pig 51-79 Poultry 20-30  Polycythemia too much RBC  Oligocythemia less RBC  Anaemia Polycythemia/erythrocytosis  A condition of increased number of RBCs in the circulation; two types: 1. Physiological (secondary) polycythemia  As a compensatory measure e.g. tissues become hypoxic because of too little oxygen in the atmosphere, for example at high altitude or higher affinity for because of failure of delivery of oxygen in the tissues as in cardiac o2 due to higher failure, then the blood forming organs automatically produce large altitudes quantities of extra RBCs i.e. 30% above the normal  Increased Hb requirement during heavy muscular exercise to meet increased oxygen demand; in sport animals (racehorse, hunting dogs) RBC elevation is a normal feature  Increased environmental stress, the splenic contraction, and increased RBC synthesis by the bone marrow cause increased number of RBCs into the circulation  Hemoconcentration due to water loss - vomiting, diarrhoea, prolonged high fever and burns 2. Pathological polycythemia research  Due to decreased O2 supply to the tissue, chronic carbon monoxide poisoning, myeloid (bone marrow) cancer, pulmonary emphysema, repeated hemorrhage  Polycythemia vera is the condition due to bone marrow cancer (myeloid leukemia); it occurs as a result of genetic aberration in the hemocytoblastic cell line that produces the blood cells Oligocythemia  Reduction in the number of erythrocytes in the circulation 1. Physiological oligocythemia occurs due to hemodilution e.g. pregnancy 2. Pathological oligocythemia is also known as anaemia Anaemia  Abnormal reduction in the number of the erythrocytes or the hemoglobin content in the blood or both  Some causes:  Excessive whole blood loss – hemorrhage  Impaired RBC production and Hb synthesis - deficiency of Fe, Cu, Vitamin B12 and folic acid  Hemolytic - caused by blood parasites or drugs (sulphanamides, antimalarial drugs)