Blood Blood is the body s interior river of life It is blood s uniqueness as a liquid tissue that makes it so interesting to study In the previous chapter blood s role in transporting hormones around the body was explained in this chapter this key role of transport extends to nutrients metabolic wastes agents that combat injury and microbial infection and of course oxygen Blood is composed of formed elements and plasma The formed elements are erythrocytes leukocytes and platelets The physical characteristics of blood including color pH and temperature are presented followed by a description of the plasma composition The next section provides a detailed analysis of each of the formed elements The function of erythrocytes as carriers of oxygen is explained highlighting the role of hemoglobin in this capacity General characteristics of leukocytes are described and then differentiated into granulocytes and agranulocytes with the role of the cell types each category presented Platelets also called thrombocytes for their clotting ability are the last of the formed elements to be analyzed Hematopoiesis of the formed elements is presented in detail including the role of erythropoietin with the differentiation of hemocytoblasts into lymphoid and myeloid stem cells The phases of hemostasis or clot formation are outlined next followed by a summary of the homeostatic imbalances associated with hemostasis which include undesirable clotting and bleeding disorders such as thrombus formation or hemophilia The final section of the chapter explains blood blood type and its impact on blood transfusions The four ABO blood groups are presented first along with a discussion of the phenomenon of agglutination which elicits the symptoms of a transfusion reaction Accompanying the presentation of Rh blood groups is an explanation of erythroblastosis fetalis or hemolytic disease of the newborn Blood The only fluid tissue in the human body Classified as a connective tissue Components of blood 1 Living cells called FORMED ELEMENTS o Erythrocytes red blood cells transports oxygen and carbon dioxide o Leukocytes white blood cells defend body against pathogens o Platelets cell fragments formed from megakaryocytes important in blood clotting 2 Non living matrix plasma is the fluid and solutes Blood Hematocrit and Beyond When blood is centrifuged Erythrocytes sink to the bottom 45 of blood a percentage known as the hematocrit BUFFY coat contains leukocytes and platelets less than 1 of blood the buffy coat is a thin whitish layer between the erythrocytes and plasma Plasma rises to the top 55 of blood Average blood volume o Women 5 0 L o Men 5 5 L Physical Characteristics of Blood Blood is used as a vehicle of transport Color range o Oxygen rich blood is scarlet red o Oxygen poor blood is dull red pH between 7 35 7 45 7 4 Blood temperature is slightly higher than body temperature at 38 100 4 degrees Blood makes up 8 of body weight Blood Plasma is 90 Water 6 8 proteins which increase osmotic pressure buffer H increase blood viscosity provide fuel during starvation 3 Major Classes of Plasma Proteins synthesized in liver except some globulins synthesized by lymphocytes Albumins Major contributor to plasma oncotic osmotic pressure and act as carriers Globulins Carriers Clotting factors Precursor proteins angiotensinogen Immunoglobulins Fibrogen BLOOD CLOTTING Nutrients glucose amino acids lipids vitamins Wastes urea bilirubin creatinine Gases dissolved oxygen carbon dioxide Hormones Relatively high concentrations of Na and Cl Relatively low concentrations of H HCO3 K and Ca2 Electrolytes Ringer s Solution A solution of distilled water containing 8 6g sodium chloride 0 3g potassium chloride and 0 33g calcium chloride per liter the same concentrations as their occurrence in body fluids This solution is ISO METRIC to our blood and tissues Why Blood Plasma Acidosis blood becomes too acidic Alkalosis blood becomes too basic In each scenario the respiratory system and kidneys help restore blood pH to normal Carbon dioxide can dissolve in water blood plasma and form CARBONIC ACID CO2 H2O H2CO3 carbonic acid H HCO3 bicarbonate Cellular or Formed Elements erythocyte Red blood cells RBCs Platelets cell fragments Leukocytes White blood cells WBCs Developmental Aspects of Blood Cells Sites of blood cell formation The fetal liver and spleen are early sites of blood cell formation Bone marrow takes over HEMATOPOIESIS by the seventh month Fetal hemoglobin differs from hemoglobin produced after birth fetal hemoglobin has a gamma subunit in place of the beta subunit and higher affinity for oxygen Physiologic jaundice results when the liver cannot rid the body of hemoglobin breakdown products fast enough Erythrocytes Erythrocytes red blood cells or RBCs Main function is to carry oxygen Anatomy of circulating erythrocytes o biconcave disk large surface area which favors diffusion o Essentially bags of hemoglobin o Anucleate no nucleus o Contain very few organelles o No MITOCHONDRIA o Use anaerobic glycolysis 5 6 billion RBCs per ml of blood Flexible membrane Also function to maintain osmolarity and blood plasma pH Hb binds strongly but reversibly to oxygen Hemoglobin in RBCs 98 5 oxygen bound to Hb and 1 5 dissolved in plasma Each hemoglobin molecule has four oxygen binding sites Globin 4 heme groups 4 polypeptides and Heme iron containing group IRON containing protein Can also bind to CO2 and H Formation of Erythrocytes Mature RBCs are unable to divide grow or synthesize proteins Wear out in 100 to 120 days When worn out RBCs are eliminated by phagocytes in the spleen or liver Lost cells are replaced by division of hemocytoblasts in the red bone marrow Iron is a component of HEMAGLOBIN Normal hemoglobin content of blood Men 13 18 gram dL Women 12 16 gram dL Control of Erythrocyte Production Rate is controlled by a hormone ERYTHOPROTIEN Kidneys produce most erythropoietin as a response to reduced oxygen Homeostasis is maintained by negative feedback from blood oxygen levels in the blood levels Control of Erythrocyte Production Hemoglobin in RBCs o Homeostatic imbalance of RBCs Anemia is a decrease in the oxygen carrying ability of the blood o Sickle cell anemia SCA results from abnormally shaped hemoglobin due to gene mutation on the Beta subunit of HB POLYCYTHEMIA is an excessive or abnormal increase in the number of erythrocytes Anemia Decrease in the oxygen carrying capacity of blood Dietary ANEMIA Iron iron deficiency anemia
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