Question

What is the body's first line of defense against bacteria and viruses?

Answer 1

Physical barrier, the skin and chemical barriers of the body act as first line of defence.

Explanation:

Dead keratinised skin of the body is a great protective layer.

The inner lining of upper respiratory tract is lined all along by cilia and mucus secreting cells, together they prevent particulate matters entering with air to enter lungs.

Chemical barrier lysozyme is present in saliva, tear as well as in sweat. The enzyme is bacteriolytic, so is HCl of stomach .

Even outward forceful flow of urine help in preventing infections.