First, Second, and Third Lines of Defence (Biology)

1. First and second lines of defence are inborn and non-specific.

2. Inborn means that these lines of defence are derived from inside our body, and non-specific means that these lines of defence attack many types of pathogens. *Pathogens are harmful and desease-causing microorganisms*

3. First line of defence is the skin and mucous membrane, while the second line of defence are phagocytes (white-blood cells).

4. Chemicals in the first line of defence include lysozyme (present in sweat, tears, saliva, and nasal secretion), sebum(secreted from skin), and mucus.

5. When pathogens succeed in penetrating the skin and mucous membrane, the second line of defence kicks in. Basically, its the process of phagocytosis.

6. common types of phagocytes are neutrophils and macrophages.

7. Simple description of phagocytocis; the phagocyte extends its plasma membrane around the pathogen, engulfing it. The pathogen trapped in a phagosome, which is a space inside the phagocyte. Lysosomes then attach to the phagosome and becomes phagolysosome. Pathogen inside the phagolysosome is digested by enzymes and acids. Waste is discharged from phagocyte.

8. Some Third line of defence terms; immunity, antigen, antibody, and lymphocytes.

9. Immunity is the ability of the body to resist infection. (immunity=ability)

10. Antigen (short for antibody generator) is a foreign protein molecule that stimulates the production of specific antibodies.

11. Antibody is a protein substance produced by the immune system in response to the recognition of a specific antigen.

12. Lymphocytes are also white blood cells. Specifically, B-lymphocytes produce the antibodies that destroy the pathogens.

a lymphocyte

13. The third line of defence is aqquired and specific, meaning that they are triggered by substances outside the body, and they are specific in their action of defence.