Antibodies, also called immunoglobulins, are proteins manufactured by the body that help fight against foreign substances called antigens. When an antigen enters the body, it stimulates the immune system to produce antibodies. (The immune system is the body's natural defense system.) The antibodies attach, or bind, themselves to the antigen and inactivate it.<span>
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Respiratory system is refers to as the organs which are involved in breathing such as nose, throat, larynx, trachea, bronchi, and lungs. It is also known as respiratory tract.
The circulatory system is refer to as which contains the heart and the blood vessels and blood moves throughout the body in vessels. This circulatory system helps tissues to get enough oxygen and nutrients, and it helps them get rid of waste products.
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What is breathing?</h3>
When person inhale (breathe in), air enters in the lungs, and oxygen from atmosphere moves to body blood. At the same time, carbon dioxide, a waste gas, moves from blood to the lungs and is exhaled (breathed out).
Breathing process is known as gas exchange which is is essential to life.
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