How does the body protect itself from infections?

The human body has several defense mechanisms to help protect itself from infections caused by microorganisms such as bacteria, viruses, fungi, and parasites:

1. Physical Barriers:

- Skin: The outermost layer of the body acts as a physical barrier, preventing microorganisms from entering the body.

- Mucous Membranes: These line various body cavities, such as the respiratory, digestive, and urogenital tracts, and produce mucus that traps microorganisms.

- Saliva, Tears, and Stomach Acid: These contain antimicrobial substances that can destroy microorganisms.

2. Innate Immune System:

- Phagocytes: Cells such as neutrophils and macrophages engulf and destroy microorganisms.

- Natural Killer (NK) Cells: These cells can recognize and destroy infected or cancerous cells.

- Cytokines: Chemical messengers released by immune cells that help coordinate the immune response.

- Complement System: A group of proteins that enhance the ability of phagocytes to kill microorganisms.

- Inflammation: A localized response to tissue damage or infection, characterized by redness, heat, swelling, and pain.

3. Acquired Immune System:

- Antibodies: Specialized proteins produced by B cells that bind to specific antigens on microorganisms and neutralize them.

- T Cells: There are different types of T cells:

- Cytotoxic T cells: Directly kill infected cells.

- Helper T cells: Help activate B cells and cytotoxic T cells.

- Memory T cells: Remain in the body and quickly mount a response if the same pathogen is encountered again.

- Immunological Memory: Allows the immune system to mount a faster and more efficient response to previously encountered pathogens.

4. Microbiota:

- The body harbors trillions of non-harmful or beneficial microorganisms, collectively known as microbiota. These microorganisms help compete with harmful bacteria and contribute to the body's overall defense system.

5. Vaccination:

- Vaccination involves introducing a weakened or killed form of a microorganism into the body, stimulating the immune system to produce antibodies without causing disease. This provides protection against future infections by the same pathogen.

These mechanisms work together to provide multiple layers of defense against infections. When one or more of these defense mechanisms are compromised, the body becomes more susceptible to infections and diseases.