Answer
The human body employs a multi-layered defense system against pathogens:
1. **Physical and Chemical Barriers (First Line of Defense):** These include the skin, mucous membranes, and various secretions like tears, saliva, and stomach acid. They create physical barriers that prevent pathogens from entering the body, and some of these secretions have antimicrobial properties that can neutralize pathogens.
2. **Innate Immune Response (Second Line of Defense):** If pathogens breach the first line of defense, the innate immune system activates. This involves immune cells like macrophages, neutrophils, and natural killer cells. These cells recognize common features of pathogens and trigger inflammation to contain and destroy them. The release of cytokines also recruits more immune cells to the site of infection.
3. **Adaptive Immune Response (Third Line of Defense):** If the innate immune response is insufficient, the adaptive immune system comes into play. This system involves specialized immune cells called T cells and B cells. T cells coordinate immune responses and directly attack infected cells, while B cells produce antibodies that target specific pathogens. This response leads to immunological memory, providing long-term protection against future encounters with the same pathogen.
Together, these three lines of defense provide a comprehensive and dynamic defense against a wide range of pathogens.
Work Step by Step
The human body employs a multi-layered defense system against pathogens:
1. **Physical and Chemical Barriers (First Line of Defense):** These include the skin, mucous membranes, and various secretions like tears, saliva, and stomach acid. They create physical barriers that prevent pathogens from entering the body, and some of these secretions have antimicrobial properties that can neutralize pathogens.
2. **Innate Immune Response (Second Line of Defense):** If pathogens breach the first line of defense, the innate immune system activates. This involves immune cells like macrophages, neutrophils, and natural killer cells. These cells recognize common features of pathogens and trigger inflammation to contain and destroy them. The release of cytokines also recruits more immune cells to the site of infection.
3. **Adaptive Immune Response (Third Line of Defense):** If the innate immune response is insufficient, the adaptive immune system comes into play. This system involves specialized immune cells called T cells and B cells. T cells coordinate immune responses and directly attack infected cells, while B cells produce antibodies that target specific pathogens. This response leads to immunological memory, providing long-term protection against future encounters with the same pathogen.
Together, these three lines of defense provide a comprehensive and dynamic defense against a wide range of pathogens.
