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What are the primary defences against pathogenic bacteria?

The primary defences against pathogenic bacteria are the immune system, physical barriers, and beneficial bacteria.

The immune system is the body's primary defence against pathogenic bacteria. It is composed of a complex network of cells, tissues, and organs that work together to protect the body. The immune system can be divided into two main parts: the innate immune system, which you are born with, and the adaptive immune system, which you develop when your body is exposed to microbes or chemicals released by microbes. The innate immune system includes physical barriers like skin and mucous membranes, which trap bacteria, and cells like neutrophils and macrophages, which engulf and destroy bacteria. The adaptive immune system includes cells like B cells, which produce antibodies that can bind to specific bacteria and neutralise them, and T cells, which can kill infected cells.

Physical barriers are another important defence against pathogenic bacteria. The skin, the body's largest organ, acts as a physical barrier that prevents bacteria from entering the body. The mucous membranes that line the respiratory, gastrointestinal, and urogenital tracts also serve as physical barriers. They produce mucus, a sticky substance that can trap bacteria and other particles. In addition, the cilia (tiny hair-like structures) on the surface of the mucous membranes can move in coordinated waves to push the mucus and trapped particles out of the body.

Beneficial bacteria, also known as the microbiota or microbiome, are another key defence against pathogenic bacteria. These bacteria live on the skin and in the gut, where they compete with pathogenic bacteria for nutrients and space, preventing the pathogenic bacteria from multiplying and causing infection. Some beneficial bacteria can also produce substances that inhibit the growth of pathogenic bacteria. Furthermore, the microbiota can stimulate the immune system, enhancing its ability to fight off pathogenic bacteria.

In conclusion, the body has a range of defences against pathogenic bacteria, including the immune system, physical barriers, and beneficial bacteria. These defences work together to prevent bacteria from entering the body, neutralise bacteria that do enter the body, and maintain a healthy balance of bacteria in the body.

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