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How does skin prevent bacteria and other germs from entering the body?
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immune system
Stimulation of immune response by activated helper T cells. Activated by complex interaction with molecules on the surface of a macrophage or some other antigen-presenting cell, a helper T cell proliferates into two general subtypes, TH1 and TH2. These in turn stimulate the complex pathways of the cell-mediated immune response and the humoral immune response, respectively.
The skin serves as a vital component of the body's innate immunity by acting as a primary external barrier against infection. It protects the body through both mechanical and chemical defenses:
- Mechanical Barrier: The skin features a tough, durable outer layer of cells that produce keratin. This layer is constantly renewed from beneath, providing a physical shield that prevents pathogens from entering the body.12
- Chemical Defense: Skin glands secrete oily substances containing fatty acids, such as oleic acid, which are capable of killing certain bacteria. Additionally, these glands produce lysozyme, an enzyme that destroys bacteria by breaking down their outer cell walls.1
The critical nature of this barrier is highlighted by the fact that individuals with severe burns—which compromise the integrity of the skin—are highly susceptible to infections from bacteria that are typically harmless.1