Biological barriers work through a combination of physical, chemical, and cellular mechanisms.
- Physical Mechanisms: The skin acts as a physical shield, while mucous membranes trap pathogens. Cilia in the respiratory tract move mucus and trapped pathogens out of the lungs.
- Chemical Mechanisms: Secretions such as stomach acid and enzymes in saliva neutralize pathogens. The acidic pH of the skin and stomach creates an inhospitable environment for many microbes.
- Cellular Mechanisms: Immune cells like macrophages engulf and destroy pathogens. Dendritic cells capture antigens and present them to T cells, initiating an adaptive immune response.
