Characteristics of blood

• Blood (in vivo)


  Red, fluid state
• Blood (in vitro)


  Coagulates in 5-10 minutes
• Blood color


  • Arterial blood: bright red (oxygenated)
  • Venous blood: dark purplish red (deoxygenated; waste products)
• Blood


  • Thick and viscous (3.5 -4.5x more viscous tan water)
  • Average specific gravity of 1.055
  • Average pH of 7.40 (7.35-7.45)
  • Maintained by excretion of carbon dioxide, acid-base balance
• Blood volume


  75-85 mL per kilogram of body weight
• Blood volume by age and gender


  • Adult male: 5-6 liters
  • Adult female: 4-5 liters
  • Newborn: 250-350 ml
• Plasma

  Pink: Slight hemolysis

  Red: Gross hemolysis

  Yellow-brown: Icteric plasma ⬆️ bilirubin
• Plasma

  90% water, 10% solutes
• <1/3 central palor : ⬆HGB concentration

  >1/3 central palor : ⬇HGB concentration
• Fatty layer : Upper most layer of centrifuged blood
• Automated cell counters

  coulter counter principle : electric impedance
• Gold standard for HGB determination : CYANMETHEMOGLOBIN (HiCN) method
• CYANMETHEMOGLOBIN

  • weak solution potassium cyanide and potassium ferricyanide called DRABKIN REAGENT
• Sodium Lauryl Sulfate

  • Ionic surfactant (detergent)
  • reduce environmental cyanide
• RBC INDICES


  Measures parameters of a single RBC; useful in the assessment of anemia
• Mean cell/corpuscular volume (MCV)


  • Measures the volume/size of a single RBC
  • Reported in femtoliters (fl)
• Mean cell/corpuscular hemoglobin (MCH)


  • Measures the weight/mass of hemoglobin in a single RBC
  • Reported in pictograms (pg)
• Mean cell/corpuscular hemoglobin concentration (MCHC)


  Measures Hgb concentration in a single RBC; staining capacity of RBC's and amount of central pallor (g/dL)
• Red cell distribution width (RDW)

  • Based on the standard deviation of RBC volume and is routinely reported by automated blood cell analyzers
  • Measures the degree of anisocytosis
• Anisocytosis : increased variation in cell siZe

  Poikilocytosis : increased variation in cell shaPe
• Reticulocyte supravital stain

  • Brilliant cresyl blue
  • New methylene blue
  • Crystal violet
• Reference ranges

  MCV : 80-100 fL

  MCH : 26-34 pg

  MCHC : 32-36 g/dL

  RDW : 11.5-14.5 % Retics : 20-115 x109/L
• Band neutrophils

  Left shift

  • increase in bands
  • signals bacterial infection
• Neutrophils

  • phagocytic
  • pink or lavender staining granules
  • Viral infections
• Eosinopils

  • phagocytic
  • round, bright orange-red cytoplasmic granules
  • Allergic or Parasitic infection
• Basophils

  • dark purple, irregular cytoplasmic granules that obscure nucleus
  • contains histamine
• Lymphocytes

  • recognize foreign antigens
  • humoral and cell mediated
  • round, slightly larger than RBC, round featureless nuclei and a thin rim of non-granular cytoplasm
• Monocytes

  • phagocytic
  • blue gray cytoplasm
  • fine azure granules