What is in a drop of blood

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What is in a drop of blood?
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Figure 42.14 The composition of mammalian blood
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Figure 42.14x Blood smear
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Red Blood Cells

• There are about 25 trillion RBCs in the bodys 5
  L of blood
• StructureFunction
• Small biconcave disks (about 5-7mm)
• Biconcave shape creates large surface
  area/volume, which enhances O2 diffusion
• Mature RBCs do not have a nucleus
• Lack of nucleus allows more space for hemoglobin.
  Each RBC contains about 250 million molecules of
  hemoglobin, which allow each cell to carry a
  billion oxygen molecules.
• An average man has 900 g of hemoglobin in his
  blood at a concentration of 16g/dL.
• Mature RBCs do not have mitochondria
• Generate ATP exclusively by anaerobic
  respiration, which means they do not consume the
  oxygen they carry.
• Red Blood cells are constantly being generated.

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Anemia

• Too few red blood cells or too low a
  concentration of hemoglobin
• Normal men have 45 hematocrit or 16g/dL
  hemoglobin
• Normal women have 42 hematocrit or 14g/dL
  hemoglobin
• Symptomatic anemia is when hemoglobin drops below
  10g/dL
• Chronic Anemias
• Iron deficiency anemia
• Iron is necessary for hemoglobin production
• B12 deficiency anemia
• Vitamin B12 is necessary for RBC production
• Potential hazard for strict vegetarians.
• Vitamin B12 comes from meats, poultry and fish.
• Blood Loss Anemias
• Sudden blood loss due to severe wound or blood
  donation.
• Recover of blood cells starts within a day, but
  continues for weeks to months.

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Where are our blood cells made?
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Bone Marrow

• One of the largest organs in the body,
  approaching the size and weight of the liver.
• One of the most active tissues in the body.
• Contains stem cells and blood cells at different
  stages in development.
• Since white blood cells have a shorter life span
  than red blood cells, twice as many cells in the
  marrow are producing white blood cells.
• The average life of a RBC is 120 days, whereas
  for a white cell it is a couple of hours.

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Figure 42.15 Differentiation of blood cells
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Normal Marrow Cells
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Platelets

• Pinched off fragments of giant cells in the bone
  marrow (megakaryocytes).
• Like RBCs they do not contain a nucleus.
• Platelets are vital for blood clot formation.
• When blood vessels are injured, platelets adhere
  to the exposed collagen in the basement
  membranes.
• When bound to the basement membrane, platelets
  release a substance that attracts additional
  platelets.
• The clump of platelets promotes clotting, which
  ultimately cause fibrinogen to be converted to
  fibrin. Fibrin reinforces the clump of platelets.
• The major clotting factor is thrombin.
• The rat poison warfarin (coumadin) interferes
  with this process and is used clinically to
  inhibit clotting.

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Figure 42.16x Blood clot
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White Blood Cells

• Well discuss these when we discuss the immune
  system - Lets discuss instead how hemoglobin
  binds and releases oxygen

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Hemoglobin
Every molecule of hemoglobin binds 4 oxygen
molecules
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The Air We Breathe

• Our atmosphere is composed of 21 oxygen, and at
  sea level the pressure is 760 mm Hg.
• At sea level the partial pressure of oxygen is
  equal to the atmospheric pressure times the
  percent of air that is oxygen (760mm x .21) or
  160 mm Hg.
• The partial pressure for CO2 is .23 mm Hg.
• Gases will diffuse from a high partial pressure
  to a lower partial pressure.

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Figure 42.27 Loading and unloading of
respiratory gases

• Air entering the lung has a high PO2 and a low
  PCO2.
• Air in the alveolar spaces has a lower PO2 and a
  higher PCO2
• Blood entering the alveolar capillary bed has an
  even lower PO2 and higher PCO2.
• Oxygen will dissolve in the fluid surrounding the
  alveoli and diffuse into the blood stream

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Figure 42.27 Loading and unloading of
respiratory gases
By the time the blood leaves the alveolar
capillaries the PO2 of the blood has increased
and the PCO2 has decreased slightly.

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Figure 42.27 Loading and unloading of
respiratory gases
Once the blood reaches the systemic tissues, the
gradients are reversed and the oxygen diffuses
out of the blood into the surrounding tissue.

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Figure 42.28 Oxygen dissociation curves for
hemoglobin

• Hemoglobin binds oxygen in a cooperative fashion.
  The binding of oxygen to one subunit induces the
  remaining subunits to change their shape, which
  results in an increased affinity for oxygen.
• Active tissues will have a lower pH, due to
  lactic acid and carbonic acid (water CO2).
  This results in a decrease affinity of hemoglobin
  for oxygen (increased unloading of oxygen to the
  tissue)

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Transport of Carbon Dioxide

• 70 of the carbon dioxide in the blood reacts
  with H2O to form carbonic acid (H2CO3). This
  reaction is catalzyed by the enzyme carbonic
  anhydrase.
• 23 of the carbon dioxide also reacts with the
  amino groups on hemoglobin and other blood
  proteins
• 7 of carbon dioxide is dissolved directly in the
  plasma

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Figure 42.29 Carbon dioxide transport in the
blood
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Fetuses have fetal hemoglobin - Why?