histo blood

• Blood is the fluid that circulates in the cardiovascular system and is considered a form of loose connective tissue that consists of cellular elements suspended in a fluid intercellular substance known as the plasma

  
• Functions of the blood

  • Transport oxygen from the lungs and nutrients from the gastrointestinal tract to tissues
  • Carry carbon dioxide and waste materials to the organs where they are disposed of
  • Carry hormones and proteins to their target tissues or organs
  • Defend the body against invading microorganisms and toxic substances
  • Maintain acid-base balance
• Layers of blood when collected in a test tube

  • Top layer: plasma (54% of volume)
  • Thin white middle layer: buffy coat (platelets and white blood cells, 1% of volume)
  • Bottom red layer: red blood cells (45% of volume)

  
• Major plasma proteins


  • Albumin
  • Globulins (alpha, beta, gamma)
  • Complement proteins
  • Clotting factors
  • Plasma lipoproteins
• Albumin


  Smallest but most abundant plasma protein, maintains colloid osmotic pressure and transports some molecules
• Globulins


  Transport metal ions, protein-bound lipids, lipid-soluble vitamins, and antibodies for host defense
• Complement proteins


  Involved in the inflammatory and immune responses, destroy microorganisms
• Clotting factors


  Involved in the formation of blood clots
• Plasma lipoproteins


  Transport triglycerides and cholesterol to/from the liver
• Formed elements of blood

  • Erythrocytes (red blood cells)
  • Platelets (thrombocytes)
  • Leukocytes (white blood cells)

  
• Types of leukocytes


  • Granulocytes (neutrophils, eosinophils, basophils)
  • Agranulocytes (lymphocytes, monocytes)
• Erythrocytes (red blood cells)

  • Biconcave disk shape, 8 µm diameter, 2 µm at thickest point, 1 µm at thinnest, flexible to pass through capillaries, no nucleus, contain hemoglobin, life span of 120 days

  
• Platelets


  • 2-3 µm in diameter, non-nucleated cell fragments derived from megakaryocytes in bone marrow, life span of 10 days, initiate blood clots

  
• Neutrophils


  • Most abundant leukocyte, multi-lobed nucleus, contain specific granules with bactericidal enzymes and proteins, and non-specific azurophilic granules (lysosomes), life span less than 1 week, primarily antibacterial function
• The average values for the white blood cell differential count among normal people are neutrophils 60%, eosinophils 4%, basophils less than 1%, lymphocytes 27%, and monocytes 8%

  
• Staining methods used for routine blood and bone marrow smears include Giemsa, Jenner, Wright, and Leishman
• Red blood cells appear as pink circles with light centers in blood smears, due to their biconcave shape

  
• Platelets appear as small basophilic fragments, often in clusters, in blood smears
• Neutrophils appear larger than red blood cells in blood smears, with a multi-lobed nucleus and small, neutrally stained specific granules, as well as larger azurophilic non-specific granules

  
• Lysozyme


  Enzyme that digests bacterial cell wall
• Neutrophils


  • About 9-12 µm in diameter (larger than RBC)
  • Nucleus long and multi-lobed (usually 2-4 lobes)
  • Cytoplasm has small, neutrally stained specific granules
  • Non-specific granules are azurophilic
• Neutrophils are primarily antibacterial
• TWO NEUTROPHILS IN A BLOOD SMEAR

  • Multi-lobed neutrophils in the blood smear

  
• Eosinophils


  • Nucleus contains only 2-3 lobes, usually 2 lobes
  • Chromatin material is finer than the neutrophils
  • Specific cytoplasmic granules contain several distinct cationic proteins and a variety of hydrolytic enzymes
  • Azurophilic granules are fewer and smaller than their specific granules
  • Limited phagocytic activity, do not phagocytose bacteria
  • Defend the body against parasites, especially round worms, by releasing the content of their granules in the extracellular environment
• Eosinophil life span


  < 2 weeks
• Eosinophil granules


  • Major basic protein
  • Lysozyme
  • Eosinophilic cationic protein
  • Acid hydrolase
  • Neurotoxin
  • Myeloperoxidase
  • Histaminase
  • Elastase
• Eosinophils


  • About 10-14 µm in diameter
  • Bi-lobed nucleus
  • Cytoplasm has prominent pink/red specific granules (stained with eosin dye)
  • If the smear is not stained properly, the granules may be brownish
• Eosinophil function

  • Anti-parasitic activity
  • Mediators of inflammatory/allergic responses in tissues
• EOSINOPHIL IN A HUMAN BLOOD SMEAR

  • Bilobed eosinophil in a human blood smear

  
• Eosinophil in TEM


  • Specific granules are ovoid in shape, and contain a dark crystalloid body composed of major basic protein (MBP), effective against parasites
  • The rest of the granule contains other anti-parasitic substances and histaminase
  • The cytoplasm also contains lysosomes (=azurophilic granules)
• Basophils


  • Specific cytoplasmic granules are larger but fewer than those of eosinophils
  • Contain histamine, heparin and leukotrienes
  • Nucleus is usually u-shaped or j-shaped but sometimes appears bilobed
  • Similar to mast cells of connective tissue in that, both cell types have cytoplasmic granules that contain histamine and heparin
• Basophil life span


  1. 2 years
• Basophil granules


  • Histamine
  • Heparin
  • Eosinophil chemotactic factor
  • Phospholipids for synthesis of leukotrienes
  • Lysozyme
  • Acid hydrolase
  • Myeloperoxidase
  • Elastase
• Basophils


  • About 8-10 µm in diameter
  • Cytoplasm contains large, purple/black specific granules (stained with the basic dye) that are larger but not as numerous as those of eosinophils
  • Nucleus is usually bilobed, but usually is partially obscured by granules, which can lie over it
• Basophil function


  Allergies and anaphylaxis (hypersensitivity reaction)
• BASOPHIL IN TEM


  • Specific granules vary in size and shape, and have occasional myelin figures (usually formed from phospholipids)
  • Cytoplasm also has some lysosomes (=azurophilic granules)
• Lymphocytes


  • Comprised a family of cells that act as the principal agents of body's immune response
  • Classified into small and large according to size
  • In the blood, the majority are small lymphocytes with a high nucleus to cytoplasm ratio
  • Large lymphocytes have abundant cytoplasm that is intensely basophilic and a large but relatively pale nucleus
• Lymphocyte life span


  Variable (few days to several years)

  
• Small lymphocytes


  • About 8 µm in diameter
  • Round, dense nucleus (abundant heterochromatin)
  • Cytoplasm is a narrow rim around the nucleus, and when well stained is pale blue

  
• Large lymphocytes


  • Up to about 15 µm in diameter
  • Ovoid, dense nuclei (abundant heterochromatin)