The human body has two different types of defense systems, the nonspecific defense system and the specific defense system. The nonspecific defense system will respond automatically to any and all foreign substances,it is comprised of the mucous membranes and the skin. Inflammatory responses as well as a substantial amount of proteins, which are produced within the cells of the body, are also part of the nonspecific defense system. The purpose of this defense system is to not only try to wipe out any and all foreign pathogens, but to also ease the workload of secondary defense measures.

    The specific defense system, more commonly the immune system, is the second type of defense system within the body.  It's purpose is to comprise a specific defense measure against a pathogen. The specific defense system is not made up of actual organ structures, but it is made up of billions of cells. Thus, the specific defense system is known as a functional system, as opposed to an organ system.

The skin is the body’s first line of defense, it plays a major role in preventing disease by protecting all the organs, blood vessels, and the lymph system. Without the skin, bacteria and viruses could easily enter the blood system. The skin also houses many lymph nodes. Lymph nodes are a part of the lymph system, a network of vessels, which transport white blood cells, or phagocytes, throughout the body to combat disease.

Mucous membranes are cells that line all openings of the body. When dust particles enter the body, they get caught in the mucous membranes and are then digested. Nose hair is the body’s natural air filtration system. Nose hairs capture dust particles keeping them from accumulating in the lungs. A sneeze is the body’s way of ridding itself of accumulated dust particles.

    Mucous membranes produce a large variety of protective chemicals, which serve to either, destroy the pathogen, or to trigger a stronger immune response. The functions of the protective chemicals are, the pH of skin secretions inhibits the bacterial growth. Skin secretions produce sebum, which contains chemicals, which are toxic to bacteria. The stomach mucosa secretes hydrochloric acid (HCL) as well as other protein digesting enzymes. Both of these substances, hydrochloric acid as well as protein digesting enzymes destroy pathogens. Mucous proves to "stick" microscopic organisms, which may have entered the respiratory and digestive passageways. Lacriminal fluid and saliva contain lysozyme, a type of enzyme which is known to destroy bacteria.