What is the single most critical defense system of your body? 2. how do mucous membranes provide protection from invading organisms? 3. what is immunity? 4. explain what an antigen is. 5. what are antibodies? 6. how do b and t lymphocytes (t cells) in a body's immune system? 7. how does fever in a human body fight infection? 8. how does pain in response to infection or injury a body in response to invasion? 9. vaccinations are giving to prevent infection. how do vaccinations work? why should children and adults be given vaccinations? 10. what is active and passive immunity?

Answer 1:  

              The most critical defense system of our body is known as immune system.  

Discovery

            More than 2000 years ago, the Greek historian Thucydides observed that occasionally some-one contact a disease, recovers and never catches the disease again, the person has become immune to the subsequent infection. In 1796 an English country doctor Edward Jenner hypothesized that cowpox somehow conferred protection against smallpox.  

Components of immune system

                 Immune system is composed of three line of defense, these are:  

1. First line of defense  

                 It is non-specific defense and consist of skin, mucus and cilia.  

2. Second line of defense  

               It is also non-specific defense includes macrophages, neutrophils, natural killer cells and complement system etc.  

3. Third line of defense

            It is specific defense and accomplished by B-cells and T-cells though cell mediated immunity and humoral mediated immunity.  

Answer 2.  

First line of defense include mucus membrane and skin. It is non-specific defense. it provide protection through the following ways:

Role of mucus membrane

1. Mucus membrane cover the digestive and respiratory tract and acts as a barrier to microbial invasion.  

2. Mucus membrane line the inside of the nose to trap particles before they enter the body.  

3. Mucus add moisture to each breath to prevent he airways and lungs from becoming dry and damaged. As air passes through the nasal cavity, moisture is transferred from the mucus secreted by the lining of the nasal cavity into the air.  

4. Inside lungs a thin coat of mucus membrane is present inside alveoli which catches the dust and bacteria and swept them towards wind pipe through beating of cilia.  

Answer 3:

Definition

               The ability to resist damage from foreign substances such as microorganisms and harmful chemicals is known as immunity.  

Explanation

           Immunology is the study of immunity and the defense mechanism of the body. Immunity is one of the most important job provided to body in a number of ways, like in the form of anti-bodies, WBC, interferons etc.

Types of immunity

            Immunity may be active or passive both types are achieved naturally or artificially.  

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