Human Anatomy and Physiology

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Human Anatomy and Physiology

• Immunology Innate defenses

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Overview

• Not organ associated but comprised of cells
  inhabiting lymph and body fluids
• Innate system
• Surface membranes skin and mucosae
• Internal defenses phagocytes, fever, NK cells,
  antimicrobial proteins, inflammation
• Adaptive system
• Humoral immunity (B cell)
• Cellular immunity (T cell)

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Surface barriers

• Integument (skin)
• Multilayered skin
• Keratin stops bacterial enzymes and toxins
• Epithelial membranes
• Acidic skin secretions
• Acid stomach mucosa
• Saliva contains lysozyme
• Respiratory and digestive tract mucus

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Internal barriers

• Phagocytes
• Macrophages big-eaters
• E.g. monocytes, neutrophils

Phagocytosis - steps Engulf (1,2) Formation of
vesicle (3) Lysozome fusion (4) Digestion Exocytos
is (5)
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Internal barriers

• Natural killer cells
• Non-specific killers (e.g. viruses, cancer cells)
• Recognize sugars on surface of target cell
• Attacks target cells membrane releasing
  perforins
• nuclear disintegration and inflammation

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Internal barriers

• Inflammation
• Signs
• Redness, heat, swelling, pain, impairment of
  function
• Inflammatory process
• Receptors on cell surface release chemicals
  (histamine, kinins, etc.)
• Cause small blood vessels to dilate redness and
  heat
• Chemicals increase capillary permeability, fluid
  causes edema, edema causes pain

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Inflammation

• Aids healing process
• Dilution of harmful substances
• Oxygen and nutrients
• Clotting proteins

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Inflammation

• Phagocyte mobilization follows inflammation
• Process
• Leukocytosis (1)
• Margination (2)
• Diapedesis (3)
• Chemotaxis (4)

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Internal barriers

• Viruses cannot replicate themselves
• How viruses work
• Antimicrobial proteins - interferon

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Interferons

• Steps
• Virus enters host and replicates
• Infected cells secrete interferons
• Interferons stimulate production of antiviral
  proteins
• Antiviral proteins prevent virus replication

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Internal barriers

• Fever

Liver and spleen sequester iron and zinc during
fever Speeds up metabolism