Defence system Flashcards
Define pathogen
An infectious organism that causes disease or illness in a host
Define active immunity
Defence against a pathogen by antibody production in the body, long-term (memory cells)
Skin as a barrier
Physical barrier
Acidic pH to prevent growth of organisms
Sweat and oil secretions kill many bacteria
Respiratory tract as a barrier
Mucus trap organisms
Cilia sweep away mucus
Conjunctiva of the eye as a barrier
Physical barrier
Mucus-secreting epithelial membrane
Kept moist by tears
Gastric juice of the stomach
Acidic pH
Kills bacteria food in food
Chemical barriers such as urine and vaginal fluids
Low pH
Lysozomes as a chemical barrier
Enzyme produced in tears, sweat, saliva which breaks down the walls of bacteria
Lymphocyte- Antibody production
- Lymphocyte comes into contact with pathogens
- Antigen alerts the lymphocyte to produce antibodies
- Antibody-antigen complex
- Pathogen is deactivated and memory cells are created.
Where are memory cells stored
In the lymph nodes
Phagocytosis
1.Phagocyte is attracted to pathogen and attaches to pathogen
2. Phagocyte engulfs pathogen
3. Lysosomes release enzymes that digest pathogens
Explain the role of vaccination in controlling the spread of disease
- Individual immunity
- Herd immunity
- Eradication of diseases
- Reduce disease transmission
Define passive immunity
A short-term defence against a pathogen by antibodies acquired from another individual, no memory cells produced
Define vaccination
Person given a dead or weak form of a pathogen to stimulate the body to produce antibodies and memory cells
Events leading to active immunity
Natural- exposure to pathogen
Vaccination
Both produce memory cells
