First Level of Defence
The first line of defence act as the physical and chemical barriers which prevent foreign substances from entering the organism.
Physical Barriers:
Chemical Barriers:
Physical Barriers:
- Intact skin acts as a barrier so that most pathogens cannot pass through.
- Cilia found in the throat are small hairlike structures that move foreign substances into the stomach where they are exposed to stomach acid so it can be digested.
- Ear and nose hairs block entry of pathogen into the body.
- Ear wax is sticky allowing pathogens to be trapped into place until they can be removed.
- Natural flora are non-pathogenic agents bacteria which are found in skin spaces, preventing pathogenic bacteria entry.
Chemical Barriers:
- Mucus secretion which helps trap micro-organism so that they can be handled elsewhere so that they are not harmful to the organism.
- Saliva contains enzymes which helps breakdown bacteria preventing it from entering internally.
- Sweating has a dehydrating effect on the pathogen so that it is prevented from harming the body.
- Tears flush pathogen away from the eyes and contain lysozyme which breakdown cell walls of bacteria.
- Stomach acid has unfavourable pH levels for micro-organisms.
First Line of Defence in Humans