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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Answer:
The cell membrane, therefore, has two functions: first, to be a barrier keeping the constituents of the cell in and unwanted substances out and, second, to be a gate allowing transport into the cell of essential nutrients and movement from the cell of waste products.
Explanation:
