lesson 6

• Disease


  A condition that disturbs the normal functioning of the organism
• Disease


  Consequently, the body can no longer maintain homeostatic processes
• Illness


  A deterioration in the state of normal health
• Infection


  The invasion of an organism's body tissue by disease-causing agents
• Immune system

  • Prevent infectious agents invading body tissues
  • Respond to successful infections in order to restore normal health
• Disease

  A condition that disturbs the normal functioning of the organism
• Homeostasis

  The body's ability to maintain normal functioning
• Illness

  A deterioration in the state of normal health
• Infection

  The invasion of an organism's body tissue by disease-causing agents
• Immune system

  • Prevents infectious agents invading body tissues
  • Responds to successful infections in order to restore normal health
• Pathogen

  A disease-causing agent that disrupts normal physiology
• Types of pathogens

  • Cellular (living)
  • Acellular (non-living)
• Cellular pathogens

  • Parasites
  • Protozoa
  • Fungi
  • Bacteria
• Acellular pathogens

  • Viruses
  • Prions
• Lymphatic system

  Protects the body from pathogens via two inter-related fluid systems: the blood system and the lymph system
• Blood system

  Produces the body's immune cells (leukocytes) and transports them to sites of infection
• Lymph system

  Corresponding drainage system comprised of lymph that is responsible for filtering blood and tissue fluid
• Lymph

  A clear fluid containing white blood cells that arises from the drainage of fluid from blood and tissues
• Lymph nodes

  Points where lymph is filtered and pathogens are targeted for destruction and removal
• Lymphoid organs

  • Spleen
  • Thymus
  • Tonsils
  • Appendix
• Leukocytes

  White blood cells responsible for the immune response
• Types of leukocytes

  • Neutrophils
  • Lymphocytes
  • Monocytes
  • Eosinophils
  • Basophils
• Innate (non-specific) immune response

  • Rapid response
  • Kills parasites
  • Initiates inflammation
  • Longer lasting
• Adaptive immune response

  • Specific targeted response
• Lines of defense in the immune system

  • Non-specific defences (innate immunity)
  • Specific defences (adaptive immunity)
• Non-specific defences (innate immunity)

  First line of defense
• Surface barriers

  • Skin
  • Mucous membranes
  • Secretions of skin and mucous membranes
• Surface barrier mechanisms

  • Removal of particles by cilia
  • Lysozyme in tears and other secretions
  • Intact skin, fatty acids
  • Commensals (normal flora)
  • Mucus lining trachea
  • Rapid pH change in gut
  • Vaginal acids (in females)
  • Flushing of urinary tract
• Clotting

  The process by which broken vessels are repaired to prevent blood loss and limit pathogenic entry
• Components of a blood clot

  • Platelets adhere to one another to form a sticky plug
  • Fibrin strands form an insoluble mesh at site of injury
• Coagulation cascade

  1. Clotting factors released

  2. Platelets become sticky and form a plug

  3. Prothrombin converted into thrombin

  4. Thrombin converts fibrinogen into fibrin

  5. Fibrin forms a fibrous clot at the plug
• Innate immunity

  The second line of defense against infection, non-specific and non-adaptive
• Components of innate immunity

  • Inflammation
  • Phagocytosis
  • Antimicrobial proteins
  • Fever
• Inflammation

  Increases capillary permeability at infected sites to recruit leukocytes
• Inflammation process

  1. Damaged cells release chemotactic factors

  2. Mast cells/basophils release histamine

  3. Localised vasodilation and increased capillary permeability
• Phagocytosis

  The engulfment and destruction of pathogens by phagocytic cells
• Complement system

  Antimicrobial proteins that augment and enhance innate immune responses
• Functions of complement system

  • Chemotaxis
  • Opsonisation
  • Membrane attack
• Fever

  An abnormally high body temperature associated with infection that reduces pathogen growth and activates heat-shock proteins
• Fever mechanism

  1. Pathogens stimulate leukocytes to produce cytokines

  2. Cytokines trigger the hypothalamus to produce prostaglandins

  3. Prostaglandins activate fever