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Lecture

February 12th, and 26th 2013.docx

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Department
Health Sciences
Course
HN320
Professor
Michael Wilkie
Semester
Winter

Description
Tuesday, February 12, 2013: Blood, Blood Flow & Blood Pressure Composition of the Blood  Platelets = pieces of cells (not whole cells)  Oxygen is dissolved in the plasma as well  Plasma contains many proteins  Fibrinogen – important for blood clotting  Diabetic coma – when the brain gets starved of glucose (seen with diabetes mellitus)  Lipids can be stored as triglycerides, transported as fatty acids  Most ammonia is converted to urea – emptied during urination  Ammonia is not organic but derived from organic molecules  Trace elements and vitamins are also present in the body  Main gases = CO2 and O2, trace levels of CO (metabolic by-product)  Albumin could be a limiting factor for kidney filtration – acts as a slow release compound, having various drugs and hormones attached to it  Albumin + Hormone  Albumin-hormone  The albumin act as a means of transport for these chemical messengers and drugs  Globulin form the antibodies critical for immune systems to develop a memory to invaders of the body Cellular Components of the Blood  Platelets are involved in initiating the clotting process  RBC contain hemoglobin – transport O2 and some CO2  WBC – capable of moving from the blood stream to interstitial fluids, generally much larger than RBC, can move through blood vessel walls  Bi-concave disk – due to loss of nuclei  actin filaments responsible for maintaining cell shape and allow flexibility  Reversible binding with hemoglobin Oxygen Delivery by RBCs  Each hemoglobin molecule has 4 subunits – 2 alpha and 2 beta  Characterized by cooperativity  difficult to bind the first oxygen to the hemoglobin molecule, after the first one binds, there is a conformational shift that makes the next heme group more accessible and this continues until all heme groups are saturated (think of it like 4 postal stamps in a square – gets easier with fewer cuts to make to remove each stamp)  Hemoglobin oxygen dissociation curve is sigmoidal in shape Production of RBC  Regulation controlled by Erythropoietin (produced and secreted by kidney cells)  As you get into higher altitudes, the partial pressure decreases (as does the concentration of atmospheric gases) – the body senses this and the kidneys release more erythropoietin  Athletes were trying to increase the numbers of red blood cells in the blood (increase the oxygen carrying capacity)  At first they introduced high altitude training camps – but you could not train as hard so instead, they started sleeping at high altitude (hypobaric oxygen tents) – and then train at lower altitudes  Spleen is also a reservoir for RBC – can get a massive amount of blood loss with rupture to the spleen  Yellow pigment (bilirubin)  also makes urine a yellow color because of breakdown of the RBC (appears also in the bile pigments)  Process of RBC formation is referred to as erythropoiesis (stimulated by EPO) – raw material for RBC production is iron (since heme groups are produced of iron)  The protein transferrin – delivers iron  Reticulocytes – immature RBC that have nuclei but as they mature they lose their nuclei and any organelles  Erythrocytes pass through large (fenestrated, quite leaky) capillaries and enter the main blood stream  Globin is eventually broken down into its constituent amino acids  Bilirubin is taken up by the liver and used for the production for bile but some remains in circulation giving a yellow color to urine  Breakdown of the RBC can also occur in the liver, iron is taken up by ferritin (acts as a means to create an iron reservoir in the liver) – liver has very high concentrations of iron  Fetal hemoglobin has gamma hemoglobin – has a higher affinity for oxygen and can grab more of the oxygen from the mother’s blood (they are breaking down fetal hemoglobin at a high rate – production of bile) – plus liver is not fully developed to break down bile  Bile containing bilirubin may also not be completely reabsorbed by the small intestine, and can be excreted in the feces (brown color)  Cyclists taking EPO can increase oxygen carrying capacity and this can increase the viscosity or the blood (since it leads to an increased hematocrit) – can increase blood pressure and can die Anemia  Iron-deficient anemia – iron is a raw material for the synthesis of RBC and RBC production will be lower than it should be and O2 carrying capacity will be lower  Pernicious Anemia – folic acid comes from leafy green vegetables, eating liver, can take folic acid supplements Measuring Hematocrit  Blood is transferred to a capillary tube that is coated with an anti-coagulant (stops the blood from clotting)  Put the blood in a centrifuge (3000 x G) for 3-5 minutes  Fill the bottom of the tube with plasticene or else there will be streams of blood around the inside of the centrifuge  Mean cell hemoglobin concentration (MCHC) – plasma is contained mostly of water, if you are dehydrated the plasma volume can go down, relative proportion of RBCs will increase  Under what conditions would the RBC swell up – hypotonic plasma (low solute concentration – caused by absorption which could be caused drinking a lot of water)  if you become dehydrated the cells might shrink  MCHC (calculation to determine if the RBC are shrinking or swelling) = concentration of hemoglobin / % hematocrit  MCHC decreases – swelling  MCHC increases – shrinking  This is why they tell you to fast before a blood test and make sure you are well hydrated  Hematocrit is slightly higher in males than females (due to menstruation)  Leukocytes – quite large, have a nucleus, organelles, main function is phagocytosis (the gobble up foreign invaders), highly mobile, can even leave the blood stream by crossing the walls of the capillaries  Thrombocytes (platelets) – cell fragments, lacking nuclei but possess mitochondria and endoplasmic reticulum Structure and Function of Blood Vessels  Arterioles – the site of local blood flow control  Capillaries – gas exchange  Great veins – vena cava  Thin layer of smooth muscle surrounding the veins – can increase the tone of the vein to help promote blood flow back to the heart (in the peripheral, they act as one-way valves)  Varicose veins – gravity causes blood to get drawn to the lower parts of the body and it pools  Smooth muscle in arterials is innervated by the sympathetic nervous system  Endothelium lines the lumen of the blood vessels (the only cells that comprise capillaries) – small distance for gases, amino acids, etc. to diffuse across  The endothelia can be tightly bound (such as the blood-brain barrier) or they could
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