Ch 19 Blood Physical Characteristics Volume o Sticky opaque fluid o Color scarlet to dark red o pH 7 35 7 45 o 38 C o 8 of body weight o Average Volume 5 6 L for males 4 5 L for females Functions of Blood 1 Distribution of O2 and nutrients to body cells Metabolic wastes to the lungs kidneys for elimination Hormones from endocrine organs to target organs 2 Regulation of Body temperature by absorbing distributing heat Normal pH using buffers Adequate fluid volume in the circulatory system o Plasma proteins platelets initiate clot formation 3 Protection against Blood loss Infection o Antibodies o Complement proteins o Immunity Blood Composition o Blood a fluid connective tissue composed of 1 Plasma 2 Formed elements Erythrocytes RBCs Leukocytes WBCs Platelets Plasma o Plasma is 92 water with dissolved solutes consisting mostly of various proteins electrolytes gasses Blood Plasma o Nitrogenous by products of metabolism Lactic acid urea creatinine Glucose other carbohydrates amino acids o Nutrients o Electrolytes o Respiratory gases O2 and CO2 o Hormones Na K Ca2 CL HCO3 Constituents of Blood Formed Elements o Red blood cells RBCs make up the bulk of the blood cells with many fewer white blood cells WBCs interspersed in among them The normal RBC mass is between 40 45 by volume the hematocrit Hct Hematocrit o Percent of blood volume that is RBCs o 47 5 for males o 42 5 for females Formed Elements Only WBCs are complete cells RBCs have no nuclei or organelles Platelets are cell fragments Most formed elements survive in the bloodstream for only a few days Most blood cells originate in bone marrow and do not divide WBCs by number make up between 5 10 x 103 mm3 o There are 5 different types of WBCs all with varying functions Megakaryocytes are huge cells that splinter into 2000 to 3000 fragments while still in the red bone marrow o Each fragment enclosed by a piece of the plasma membrane is a platelet o Platelets leave the red bone marrow enter the circulation as an irregularly shaped disc with many vesicles but no nucleus Platelets are more numerous than WBCs 150 400 x 103 mm3 but have a short life span 5 9 days they don t have much mass They appear as little specks interspersed among the RBCs o Their granules contain chemicals when released promote blood clotting Hematopoiesis Hematopoiesis hemopoiesis blood cell formation o Occurs in red bone marrow of axial skeleton girdles proximal epiphyses of humerus femur Hemocytoblasts hematopoietic stem cells o Give rise to all formed elements o Hormones growth factors push the cell toward a specific pathway of blood cell development New blood cells enter blood sinusoids Erythrocytes Biconcave discs anucleate essentially no organelles Contain the plasma membrane protein spectrin other proteins Filled with hemoglobin Hb for gas transport o Provide flexibility to change shape as necessary Are the major factor contributing to blood viscosity Live approx 120 days Structural characteristics contribute to gas transport o Biconcave shape huge surface areas relative to volume o 97 hemoglobin not counting water o No mitochondria ATP production is anaerobic no O2 is used in generation of ATP Erthyrocyte Function RBCs are dedicated to respiratory gas transport Hemoglobin binds reversibly with oxygen Hemoglobin structure o Protein globin 2 alpha and 2 beta chains o Heme pigment bonded to each globin chain Iron atom in each heme can bind to one O2 molecule Each Hb molecule can transport 4 O2 Red Blood Cells The characteristic RBC shape increases the self surface area gives them a high oxygen o Their shape also allows them to deform fit in small capillary beds carrying capacity Hemoglobin Hb O2 loading in the lungs o Produces oxyhemoglobin bright red o Hgb O2 HgbO2 O2 unloading in the tissues o Produces deoxyhemoglobin or reduced hemoglobin dark red CO2 loading in the tissues Erythropoiesis o Produces carbaminohemoglobin carries 20 of CO2 in the blood Erythropoiesis is the part of hematopoiesis that deals with the production of RBCs Erythropoiesis increases when states of hypoxia O2 deficiency stimulates the kidneys to release the hormone erythropoietin EPO o EPO circulates to the red marrow and speeds up the maturation and release of immature red cells Erythropoiesis red blood cell production o A hemocytoblast is transformed into a proerythroblast o Proerythroblasts develop into early erythroblasts Phases in development Regulation of Erythropoiesis Too few RBCs leads to tissue hypoxia Too many RBCs increases blood viscosity Balance between RBC production destruction depends on o Hormonal controls o Adequate supplies of iron amino acids and B vitamins Hormonal Control of Erythropoiesis Erythropoietin EPO o Direct stimulus for erythropoiesis o Released by the kidneys in response to hypoxia Causes of Hypoxia o Hemorrhage or increased RBC destruction reduces RBC numbers o Insufficient hemoglobin iron deficiency o Reduced availability of O2 high altitudes Effects of EPO o More rapid maturation of committed bone marrow cells o Increased circulating reticulocyte count in 1 2 days Testosterone also enhances EPO production resulting in higher RBC counts in males Dietary Requirements for Erythropoiesis Nutrients amino acids lipids carbohydrates Iron o Stored Hb 65 the liver spleen bone marrow o Stored in cells as ferritin hemosiderin o Transported loosely bound to the protein transferring Vitamin B12 and folic acid necessary for DNA synthesis for cell division Fate Destruction for Erythrocytes Life span 100 120 days Old RBCs become fragile and Hb begins to degenerate Macrophages engulf dying RBCs in the spleen Heme globin are separated o Iron is salvaged for reuse o Heme is degraded the pigment bilirubin o Liver secretes bilirubin in bile into the intestines o Degraded pigment leaves the body in feces o Globin is metabolized into amino acids Erythrocyte Disorders Anemia blood has abnormally low O2 carrying capacity o A sign rather than a disease itself o Blood O2 levels cannot support normal metabolism o Accompanied by fatigue paleness shortness of breath chills Causes of Anemia 1 Insufficient erythrocytes o Hemorrhagic anemia acute or chronic loss of blood o Hemolytic anemia RBCs rupture prematurely o Aplastic anemia destruction or inhibition of red bone marrow 2 Low hemoglobin content o Iron deficiency anemia Secondary result of hemorrhagic anemia or Inadequate intake of iron containing foods or Impaired iron absorption o Permicious anemia Deficiency of vitamin B12
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