The first line of defense

 The first line of defense in the human body is the chemical and physical surface barriers that prevent any foreign organism or particle from entering the body. This level of defense does not target any specific foreign object as harmful, but considers all foreign matter as harmful and builds a combination of the following chemical and physical surface barriers.So this layer is known as non-specific layer:The skin is the first part of the First line of Defense. This layer is structurally keratinous, airtight, waterproof and impermeable to most substances. It is replaced all the time.Due to its pH acidity and the presence of antibiotics derived from sweat glands, no harmful germs can survive on it. In addition to the skin, this protective layer covers the mucous membranes at all entrances to the body.Much of the mucous membrane is covered by microscopic and ever-expanding cilia.External particles and microorganisms are trapped in the adhesive mucus of the mucous membrane and are excreted as sneezing, coughing and spitting or reach the stomach.Our tears and saliva also contain lysozyme enzymes that act as bactericidal. We have a kind of yellowish brown waxy substance called seromin in our ears.It works so that the eardrum cannot be damaged by dirt or microorganisms.The alimentary canal contains proteolytic enzymes and hydrochloric acid.In addition, the excretion and reproductive system contain a variety of acids, such as bacteria in the vagina secreting lactic acid to reduce the chances of other organisms reproducing.