Disease, Immunity and drugs

• TRANSMISSIBLE DISEASE: Caused by pathogens and can be transmitted from one host to another
• EXTERNAL DEFENSE SYSTEM:

  1. skin: Is a cornified layer of cells preventing entry of pathogen
  2. Hair: Help to filter off dust particles and bacteria from entering our respiratory tract
  3. The epithelium coverign the inner surfaces of the trachea or bronchi is covered by a layer of mucus
• The epithelium:

  • Have hair like structures named CILLIA
  • Cillia sweeps mucus un the trachea into our pharynx
  • Mucus traps dust and pathogen from air preventing them from getting into the lungs
• 4.SALIVA:

  Contains an enzyme called LYSOZOME that can kill pathogens
• 5.HCl present in stomach can also kill pathogens
• 6.Blood clotting

  Occurs when there is a cut in our skin. Preventing pathogens from entering the bloodstream
• WBC called MAST CELLS/PHAGOCYTE secrete a chemical called HISTAMINE.

  Histamine causes blood capillaries to dilate: inflammatory response

  Blood capillaries become more leaky making squeezing out of phagocytes more easily. Phagocyte then engulf and digest pathogens (phagocytosis)
• ENTRY OF PATHOGEN:

  • Direct contact
  • indirect contact
• DIRECT CONTACT: Involves direct contact with blood or body fluids of an infected person

  e.g : AIDS, hepatitis B
• INDIRECT CONTACT:

  1. By touching a contaminated surface
  2. By airbone infection- breathing in air containing droplets with pathogens
  3. By animals (vectors)
  4. By unhygenic food preparation
  5. By contaminated food or water
• CHOLERA:

  • Caused by bacterium VIBRIO CHOLERA
  • SYMPTOMS: Diarrhea, loss of water and salts ,dehydration and weakness
  • TREATMENT: Drink a solution of salts and glucose to rehydrate the body (ORT)
  • TRANSMISSION: By consumption of contaminated water or food by faeces of infected people
• HOW DOES CHOLERA CAUSE DIARRHEA:

  • The bacterium produces a toxin in the small intestine
  • This toxin binds to intestinal cells and causes reduction of absorption of Na ions by cells and increases the secretion of chloride ions into intestines
  • This lowers water potential in intestinal contents
  • Water passes out of the cells by osmosis in the intestines
  • Causes severe diarrhea resulting in dehydration and loss of ions from blood
• IMMUNTY: is the protection provided by the body's defense system against a disease
• SPECIFIC IMMUNE SYSTEM:

  • Each pathogen has its own antigen which has a specific shape
  • Lymphocytes present in the body produces antibodies that are complementary to its antigen
  • They bind to them on the surface of the pathogen leading to its destruction by phagocytes
  • Specific antibodies are produced which are complementary to an antigen therefore leading to complementary binding of antibody to antigen
• ACTIONS OF ANTIBODIES

  1. Antibodies bind to bacteria marking them for phagocytes to engulf and destroy them
  2. Antibodies bind to bacteria causing them to clump together allowing easy ingestion by phagocytes
  3. Antibodies bind to toxins produced by bacteria making them harmless. They also bind to viruses making them inactive
  4. Bind to bacterial cell causing them to burst and die
• ACTIVE IMMUNITY/ LONG TERM IMMUNITY:

  • Natual
  • Artificial- obtained through vaccination