Pathogen: Any organism or virus that causes a disease.
Diseases caused by the following pathogenic groups (Students should know 1 example
of a disease caused by each type of pathogen):
Virus Common Cold, HIV,
Influenza, Hepatitis
Bacteria Strep Throat, Gonorrhea, Pneumonia,
Tuberculosis (TB), Syphilis
Protozoan Malaria, Giardia, Amoebic Dysentary,
African Sleeping Sickness
Fungi
Athlete's Foot
Ring Worm
Flatworms Tapeworm, Liver Flukes,
Blood Flukes (Schistosomiasis)
Roundworms Hookworm, Trichinosis, Elephantiasis
a. Food- Tapeworms, botulism, salmonella, hepatitis A
b. Water
c. Aerial – flu, colds, TB, meningitis
d. Animal vector- Mosquito, fly
e. Puncture wound- tetanus, malaria, gangrene, rabies
f. Sexual Contact (VD)-
Skin and mucous membranes act as barriers against pathogens.
The outer layers of skin are dead. As long as there are no cuts or punctures,
pathogens cannot enter through the skin. Sweat contains lysozyme (enzyme) that
digests bacterial cell walls.
Mucous membranes trap pathogens. Cilia in the nose, throat & lungs flush
potential pathogens either out of the body (via mouth or nose) or into the stomach
where the action of acids kill most of them.
Defenses Against Pathogens:
a. Antibiotics are effective against bacteria but not viruses.
Antibiotics block specific metabolic pathways found in bacteria but not in eukaryotic cells. Viruses reproduce using the metabolic pathways of their host cells so they are not affected by antibiotics.
b. Antibodies- Proteins produced by lymphocyte cells in response to a foreign substance and carried on the plasma membrane of the lymphocyte. Each antibody binds only to one antigen (based on its membrane ID markers).
Antigen- Any foreign substance, usually a protein or polysaccharide that stimulates an immune response.
Acquired Immunity- Pathogen triggers antibody response. Memory cells "remember" the antigen for quick response on re-exposure. Vaccination.
c. Phagocytic leucocytes - White blood cells that identify & ingest pathogens by endocytosis. Lysosomes within the leucocytes then release digestive enzymes into the vacuoles containing the pathogens, thus destroying them!