Erythrocytes: Anatomy and Physiology

• Leukocytes


  - largest blood cells, but 1% of blood volume

  - defense & immunity

  - nucleated

  - some have granules in cytoplasm

  - detect foreign or abnormal (antigenic) material and destroy it
• Leukocytosis

  increase in WBC count
• Leukocytosis: Indicator of (3)

  infection

  trauma

  malignancy
• Leukocytes: Types (2)


  1. Granulocytes

  2. Agranulocytes
• Granulocytes


  - polymorphonuclear leukocytes

  - multi-lobed nuclei
• Granulopoiesis


  - granulocytes formation

  - common line of development

  - myeloblast to myelocyte before differentiation
• Granulocytes: Names


  represent the dyes they take up when stained
• Eosinophil: Name


  red acid dye: eosin
• Basophil: Name


  alkaline (basic) methylene blue
• Neutrophil: Name


  purple; both dyes (neutral)
• Basophil


  - high count in allergic reactions & damaged tissues

  - nucleus: U-shaped, horseshoe

  - color: blue

  - contain cytoplasmic granules
• Basophil: cytoplasmic granules' content (3)


  1. heparin

  2. histamine

  3. other substances that promote inflammation
• Heparin


  anticoagulant
• Histamine


  - inflammatory agent
• Histamine removes an allergen by (2)

  1. increased blood flow

  2. OR easy transport of substance to attack allergen
• allergen


  - antigen that causes allergy

  - stimulus that causes basophil degranulation

  - binds to antibody-type receptors on the basophil membrane
• Mast cells


  Basophils fixed in tissues
• Mast cells: Degranulation


  - within seconds of binding an allergen

  - rapid onset of allergic symptoms following exposure to e.g., pollen in hay fever
• Eosinophil

  - high count in helminthic infections

  - nucleus: bi-lobed

  - color: red

  - less active phagocytosis than neutrophils
• helminths


  - parasitic worms

  - too big to be phagocytized
• Eosinophil: Degranulation


  release of certain toxic chemicals, stored in their granules, when the eosinophil binds to an infecting organism
• Eosinophil: Allergic Inflammation


  - local accumulation occurs

  - e.g., asthmatic airway, skin allergies
• Eosinophil: Tissue Inflammation

  promoted by releasing their array of toxic chemicals
• Eosinophil: Histaminase


  - enzyme that breaks down histamine

  - its release dampens down inflammatory process
• Neutrophil


  - high count in acute bacterial infections

  - nucleus: multi-lobed

  - color: purple

  - first to respond, highly mobile

  - remove dead cells & debris from damaged tissues

  - phagocytic
• Neutrophil: Chemotaxins


  - released by damaged cells

  - attracts neutrophils to any area of infection
• Neutrophil: Diapedesis


  how neutrophils squeeze through the capillary walls in an affected area
• Neutrophil: Phagocytosis


  engulf and kill bacteria
• Neutrophil: Nuclei


  - complex

  - multi-lobed: up to 6 lobes
• Neutrophil: Granules


  - lysosomes containing enzymes

  - digest engulfed material
• Neutrophil: Lifespan


  6-9 hours in the bloodstream
• Neutrophil: Pus Contents (3)


  1. dead tissue cells

  2. dead & live microbes

  3. phagocytes killed by microbes
• Neutrophil: Lysozyme


  enzyme in lysosome that degrades microorganism
• Neutrophil: Phagosome


  - encloses microbe

  - vesicle formed by phagocyte's cell membrane

  - later on, merges with lysosome to process foreign material
• Agranulocytes


  - 25%-50% of the total leukocytes

  - large nucleus

  - no granules
• Monocytes


  - largest WBC (2-3x than RBC)

  - nucleus shape : kidney bean

  - some circulate in the blood

  - actively motile & phagocytic
• Monocytes: Macrophage


  monocytes fixed in tissues
• Monocytes: Interleukin 1 (IL-1)


  - in hypothalamus: rise in body temperature associated with microbial infections

  - globulin production by liver

  - activated T-lymphocytes production
• Why does the body temperature rise when IL-1 acts on the hypothalamus?

  To prevent proliferation of microbes
• Mononuclear Phagocyte System (MPS)


  - family of cells consisting of the blood monocytes and tissue macrophages

  - aka reticuloendothelial system

  - synthesize & release cytokines