Blood Cells

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Blood - Cells

• Al Mina, M.D.
• Erskine College

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What is blood?

• Classified as connective tissue
• Vital for interconnections between tissues

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Blood functions

• Transport oxygen
• Transport nutrients
• Remove waste
• Repair clotting
• Defense
• Temp regulation
• Transport hormones

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Content

• Approx 5 liters
• 45 cells hematocrit virtually all red cells
• Also white cells platelets
• 55 plasma

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Cell origins

• formed in bone marrow
• All originate from common stem cell
  hemocytoblasts
• Divide into cell lines based on hematopoietic
  growth factors
• Myeloid yields RBC, platelets, granulocytes
• Lymphoid yields lymphocytes

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Erythrocytes

• Biconcave disc shape
• Filled with hemoglobin (red color)
• Mature cells anucleated, no mitochondria

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Hemoglobin

• Protein composed of four separate chains
• Each chain has iron (heme)group
• Carries O2
• Oxyhemoglobin gives RBC red color
• Approx 14 g/microliter of blood
• 280 million hemoglobin molecules/RBC
• Each carries 4 molecules O2

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Figure 14.5
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Erythrocytes contd

• Approx 5 million/microliter (mm3) variable
• Formed in adult bone marrow
• Precursor form reticulocyte-enters blood
• RBC lifespan 120 days (loses membrane
  flexibility) removed by spleen or liver

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Influences on RBC production

• Oxygen carrying capacity total RBCs
• Atmospheric conditions - altitude
• O2 consumption fitness
• Illness impairing gas exchange (lung)
• Nutrition

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Erythropoietin

• Produced mainly in kidney (liver in fetus)
• Stimulated by low blood O2 levels
• Stimulates RBC production in marrow
• Neg feedback with increased O2

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Nutritional factors

• Iron most reused, but some daily intake needed
  hemoglobin
• B12 , folic acid Inc. DNA synthesis, important
  for RBC production
• Deficiency of either leads to anemia

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RBC breakdown

• Membranes lose flexibility
• Removed in spleen/liver destroyed by
  macrophages
• Heme grps broken down to iron/biliverdin
• Iron reused in marrow or stored in liver
  (ferritin)
• Biliverdin converted to bilirubin, excreted in
  bile

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Leukocytes

• Important component of defense
• Able to leave bloodstream (diapedesis)
• 5 types, two major categories

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Granulocytes
Figure 14.9
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Neutrophils

• Most common WBC (60)
• Multilobed nucleus, fine granules
• Destroy bacteria, fungi, some viruses
• Phagocytosis

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Granulocytes
Figure 14.10
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Eosinophils

• Bilobed nucleus, red granules
• Allergic response, parasites
• 3 of WBC

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Granulocytes
Figure 14.11
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Basophils

• Dark granules
• 1 of WBC
• Inflammatory response
• Histamine inflammation (increase response)
• Heparin anticlotting, increases blood flow

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Agranulocytes
Figure 14.12
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Monocytes

• Largest leukocytes
• Phagocytize larger particles (cell debris,
  bacteria, etc)
• When out of bloodstream referred to as
  macrophages
• 5 of WBC

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Agranulocytes
Figure 14.13
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Lymphocytes

• Smaller, relatively large nucleus
• 30 of WBC
• 2 types
• B cells directly attack tumor cells,
  microorganisms, transplanted cells
• T cells produce antibodies

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Platelets
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Thrombocytes

• Fragments of megakaryocytes
• Repair damaged vessels by sticking
• Release serotonin to cause vasoconstriction

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Plasma

• All non-cellular components
• 92 water

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Plasma proteins

• Albumins
• Globulins
• Fibrinogen

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Albumin

• Largest proportion of plasma proteins
• Important for maintaining osmotic pressure
• Also valuable transport protein for lipid soluble
  molecules

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Globulin

• Alpha and beta globulins
• Synthesized in liver
• Important for transport
• Gamma globulin
• synthesized in lymph
• Antibodies

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Fibrinogen

• Important component of clotting mechanism

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Other substances

• O2, CO2 , nitrogen (inert but important to
  divers)
• Nutrients - Carbs, lipids, amino acids
• Electrolytes Na, K, Cl, etc.
• Nitrogen based substances urea, creatine,
  creatinine (mostly waste products)

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Hemostasis

• Stopping bleeding from a damaged vessel
• 3 major components
• Mostly effective on small vessels
• Vasospasm constriction of vessel

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Platelet plug

• Platelets adhere to damaged vessels (collagen)
• Also change shape, adhere to each other to form
  plug
• Works on small leaks

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Coagulation

• Multiple stage process to form a clot.
• Several clotting factors involved in chain
  reaction

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Long story short

• End result is prothrombin (alpha globulin)
  converts to thrombin
• Thrombin converts fibrinogen to fibrin
• Fibrin forms mesh to entrap cells and platelets,
  forming clot
• Positive feedback system (?)

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What stops it?

• Normal endothelial cells contain antithrombin
• Clots typically form in pooled blood, not well
  circulating

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Other clot stuff

• Thrombus abnormally formed clot
• Embolus broken off clot carried in bloodstream
• Embolism blockage of vessel by embolus
• Occurs in atherosclerotic vessels or veins where
  blood has pooled

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ABO Blood Group
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Clumping of blood cells
Figure 14.22
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Blood groupings/types

• Review lab stuff