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cellular elements of blood |
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erythrocytes, leukocytes, platelets |
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white blood cells eg monocytes, lymphocytes |
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involved in blood clotting |
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blood minus the cells proteins, nutrients, ions, wastes, hormones |
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immunoglobins clotting proteins lipid escort B |
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8% of body weight 4-6 liters |
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packed cell volume the normal value (45%) is regulated; departures from this value are either adaptive or pathological |
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what does a low value of hematocrit mean? |
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what does a high value of hematocrit mean? |
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polycythemia (adaptive or pathological) |
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what is the origin of cellular elements in blood? |
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stem cells in bone marrow - mitotically active - some of daughter remains stem cells, others differentiate |
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composed of four globin chains (two beta two alpha), each with a heme group that can carry a molecule of oxygen - 250 million hemoglobin in one red blood cell - 95% of dry weight of the cell |
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a stretchable protein under the plasma membrane; confers strength to the cell Allows the red blood cells shape to be distorted in microcirculation without shearing the cell |
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generate ATP by glycolysis red blood cells have no mitochondria |
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catalyzes the formation of carbonic acid from CO2 and water CO2 + H2O -> H2CO3 H2CO3 -> H+ + HCO3- |
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hemoglobin, spectrin, glycolytic enzymes, carbonic anhydrase, no nucleus, organelles or ribosomes (more room for hemoglobin but shorter life) |
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formation of erythrocytes process takes four days from stem cell to erythrocyte begins in bone marrow is completed in circulating blood Rate: 100 million cells per minute normally balanced with erythrocyte destruction |
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destruction of erythrocytes |
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they break apart in capillaries due to mechanical stress within 3-4 month of their formation the debris is eaten by macrophages in the spleen and liver |
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Why is hemoglobin needed to carry oxygen in the blood? |
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O2 alone has low solubility in blood heme alone would carry CO not O2 |
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What does hemoglobin bind? |
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O2 and CO CO2 (kicks off O2 to diffuse into respiring tissue) binds to polypeptide H+ (also kicks off O2) bisphosphoglycerate BPG (Hb-BPG has lower affinity for O2 than hemoglobin alone, results in more O2 dumped into tissues) |
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gas exchange between tissues and blood |
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O2 diffuses down the PO2 gradient from alveolar spaces into lung capillaries and from systemic capillaries into tissues CO2 diffuses down the PCO2 gradient from tissues to systemic capillaries and from lung capillaries to alveolar spaces |
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fetal hemoglobin has different globin chains and higher affinity for oxygen than does adult hemoglobin adult: A2B2 fetal: A2Y2 |
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How to hold your breath a long time |
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have a lot of blood and store in spleen have a lot of muscle myoglobin dont work too hard |
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heart rate slows vasoconstriction in extremity splemic contraction change in buoyency less need to inhale; less sensitivity to lower blood pH |
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how can blood loss be stopped? |
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platelet plugs (form early) fibrin clots (form later) |
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small, short-lived fragments of cells do not respond to small vessel walls |
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what activates platelets? |
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collagen fibers damage to vessel walls atheroscherotic plaques |
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What happens when platelets are activated? |
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they become sticky and form a plug They send signals for blood clotting |
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clot formation smooth vessel walls anticoagulants |
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clot formation rough vessel walls sluggish blood flow Vitamin K |
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plasminogen which is activated by tissue plasminogen activator plasmin -> dissolves clots |
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what does 'cooperativity' refer to in the context of the hemoglobin molecule? How does this cooperativity contribute to the function of hemoglobin? |
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The cooperativity of hemoglobin refers to the fact that each O2 molecule that binds to hemoglobin makes the binding of the next O2 easier The way in which cooperativity contributes to hemoglobin's function can be seen in the dissociation curve. Hmeoglobin releases O2 to tissues that need it; the greater the need, the more O2 hemoglobin should release. this is what is seen in the curve. When the tissue;s PO2 decreases from 100mmHg to 80mmHg, hemoglobin's O2 saturation declines only from 98% to 95% - it does not release much O2. But when the tissue's PO2 goes from 40mmHg to 20mmHg, as it would during work or exercise, hemoglobin's saturation goes up from 70% to 35% - a 12 fold increase in the release of O2 compares to the previous situation |
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Why must erythrocytes be made continuously by the body from pluripotent stem cells? |
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Erythrocytes encounter physical stresses in their movement through microcirculation that eventually destroys them. They have no repair capabilities, owing to their lack of nuclei and gene expression, nor can they divide to replace themselves, for the same reason. Therefor they must be made in the bone marrow at the same rate at which they are destroyed |
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Agencies which monitor cheating in sports can require a hematocrit measurement for athletes as part of the testing procedure. Why? |
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An athlete with an abnormally high hematocrit value would be suspected of taking doses of the hormone that increases production of red blood cells (erythropoietin EPO) which is against the rules |
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How does the binding of hemoglobin and O2 relate to the binding of hemoglobin and CO2? Hemoglobin and H=? How do these binding affinities help the body get O2 to tissues that need it most? |
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the binding of O2 to hemoglobin occurs with an inverse affinity to the binding of CO2 and H+ to hemoglobin. In other words, the binding of either CO2 or H+ to hemoglobin lessens the affinity of O2 for hemoglobin. Since active tissues produce CO2, and since carbonic anhydrase in erythrocytes produces carbonic acid from CO2 and water, active tissues will produce two substances (CO2 and H+) that knock O2 off hemoglobin, making the O2 more available for uptake by the tissues |
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