Exam IV Study guide Chapters 17 23 Chapter 17 Blood Blood is the only fluid tissue in the body Blood is a specialized type of connective tissue in which living blood cells called formed elements are suspended in a nonliving fluid matrix called plasma Fibrous proteins become visible as fibrin strands during blood clotting other connective tissues have collagen and elastic fibers If we spin blood in a cen trifuge it will develop layers with the heavier formed elements are packed down by the centrifugal force erthrocytes the red blood cells that transport oxygen 45 of total volume hematocrit blood fraction of erthrocytes in blood Men 47 5 Women 42 5 buffy coat present at the erythrocyte plasma junction 1 of total volume leukocytes white blood cells that help to protect the body platelets cell fragments that help stop bleeding Plasma nonliving fluid matrix 55 of total volume Functions of Blood 1 Distribution Delivering oxygen from the lungs and the nutrients from the digestive tract to all the body cells Transporting metabolic waste products from cells to elimination sites lungs and Kidneys Transporting hormones from the endocrine organs to their target organs 2 Regulation Maintaining appropriate body temp by absorbing and distributing heat throughout the body and to the skin surface to encourage heat loss Maintaining normal pH in body tissues Many blood proteins and other blood borne solutes act as buffers to prevent excessive or abrupt changes in blood pH that could effect normal cell activities Also the bloods reservoir for alkaline reserve of bicarbonate ions Maintaining adequate fluid volume in the circulatory system Salts and blood proteins act to prevent excessive fluid loss from the bloodstream into the tissue space 3 Protection Preventing blood loss When a blood vessel is damaged platelets and plasma proteins initiate clot formation halting blood loss Preventing infection Drifting along in blood are antibodies complement pro in teins and white blood cells all of which help defend the body against foreign vaders such as bacteria and viruses Blood Plasma Blood plasma is a straw colored sticky fluid 90 water Composition stays relatively constant by control of homeostatic mechanisms contains over 100 different dissolved solutes including nutrients gases hor mones wastes and products of cell activity ions and proteins plasma protein most abundant plasma solute 8 by weight most produced by liver and they are not taken up by cells to be used as fuels or metabolic nutrients albumin accounts for 60 of plasma proteins Acts as a carrier for certain molecules throughout circulation important blood buffer major blood protein contributing to the plasma osmotic pressure the pressure that keeps H2O in the bloodstream Formed Elements Erythrocytes or Red Blood Cells RBC s small depressed center disc like cells 7 5um in diameter mature RBC s are bound by a plasma membrane but lack a nucleus RBC s lack organelles and are mainly bags of Hemoglobin with a few extra proteins that help maintain flexibility and the plasma membrane RBC s 97 hemoglobin transports respi tory gasses ra The biconcave shape allows for 30 more surface area than a spherical shape and there is no point within the cytoplasm that is far from the surface By generating ATP through anaerobic processes RBCs do NOT use the oxygen they are carrying making them very efficient RBCs are the major factor in blood viscosity Women usually have fewer RBC s Blood flows slower when the blood becomes more viscous and vice versa Function of Erythrocytes RBC s RBC s are transports for respiratory gases Oxygen and CO2 Hemoglobin makes RBC s red binds easily and reversibly with oxygen most oxygen in blood is bound by hemoglobin normal values of hemoglobin 14 20 grams 100mL of blood Hemoglobin made up of the protein globin bound to the red heme pigment globin consists of of 4 polypeptide chains 2 alpha and 2 beta each binding a ring like heme group Each heme group bears an atom of iron in the center A hemoglobin molecule can transport 4 molecules of oxygen one for each iron atom that can combine reversibly with 1 molecule of oxygen 1 RBC contains about 250 million hemoglobin molecules oxyhemoglobin When oxygen binds to iron assuming 3 D shape and becomes ruby red lungs to tissues deoxyhemoglobin oxygen detaches from iron hemoglobin returns to former shape and becomes dark red tissues to lungs carbaminohemoglobin about 20 of CO2 transported in the blood binds with hemoglo bin but it binds to to globins amino acids not the heme group occurs more readily when hemoglobin is in the reduced state deoxyhe moglobin Production of Erythrocytes RBC s Hematopoiesis hemopoiesis Blood cell formation oc day 100 billion cells curs in red bone marrow Up to an ounce every Hemocytoblast hematopoietic stem cell all arise from these cells which reside in the red bone marrow different blood units arise from the same place but take commited paths that are regulated by different hormones or growth factors that push the cells into specialization Erythropoiesis erythrocyte production myeloid stem cells is transformed into a proerythroblast which give rise to early erythroblasts which produce huge numbers of ribosomes during this phase cells divide many times Hemoglobin is synthesized and iron accumulates as the early turns into late erythroblasts and further into normoblasts once almost all of the hemoglobin has been synthesized the cell ejects its organelles and the nucleus degenerates allowing the cell to collapse inward biconcave shape and is now called reticulocyte reticulocytes are named because they still contain a network of ribosomes The process takes 15 days from stem cell to reticulocyte reticulocyte counts provide a rough index of RBC formation Erythropoietin EPO a glycoprotein hormone that is the direct stimulus for erythrocyte formation triggered by reduced numbers of RBC due to hemorrhage insufficient hemoglobin per RBC iron deficiency reduced availability of oxygen high altitudes pneumonia Disorders caused by abnormal erythrocytes 1 Anemia a condition in which the blood has abnormally low oxygen carrying capacity Caused by An insufficient number of red blood cells hemorrhagic anemias result from blood loss rapid or undiagnosed ulcers hemolytic anemias erythrocytes rupture or lyse prematurely transfusion of mismatched blood and certain infections can cause aplastic anemia result from destruction or inhibition of the red marrow by certain drugs and chemicals
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