Why are physical defence called the body's first line of defence against disease?

Physical defenses are called the body's first line of defense against disease because they act as immediate barriers that prevent pathogens from entering the body. These include the skin, mucous membranes, and secretions like saliva and tears, which physically block or wash away harmful microorganisms. Their role is crucial in providing an initial response to infections before the immune system is activated. By stopping pathogens at the entry points, they help reduce the likelihood of illness.