1. Respiratory system

2. What is the respiratory system?
The respiratory system is centred on the lungs. The lungs are one of the largest organs in your body.
When you inhale, you breathe in oxygen. Your body needs this oxygen to survive.

3. How does it work?
When you breathe in oxygen through your nose and mouth, it travels through the pharynx located behind your nasal cavity and past a small piece of flexible cartilage called the epiglottis. The oxygen then passes through the larynx, which enables you to speak and is located at the top of the trachea. After passing through your trachea, the air reaches your bronchial tubes, which spread out into smaller bronchi (bronchioles) like the branches of a tree inside your lungs. At the end of your bronchial tubes are little sacs called alveoli. The oxygen travels through the alveoli to your bloodstream.

4. What is part of the respiratory system?
The nostrils
 involved in air intake
Trachea (windpipe)
The trachea filters the air we inhale and branches into the bronchi.
Bronchi
The bronchi are the two air tubes that branch off from the trachea and carry atmospheric air directly into the lungs.
Lungs
Lungs are the site in body where oxygen is taken into and carbon dioxide is expelled out of.
Alveolus
Alveolus is the tiny sac like structure present in the lungs in which the gas exchange takes place.
Diaphragm
 When we breathe in, the diaphragm contracts and flattens out and pulls downward. Due to this movement the space in the lungs increases and also pulls air into the lungs.

5. Why do we need the respiratory system?
Delivery of oxygen to the blood through breathing is the primary function of the respiratory system. The respiratory system also expels carbon dioxide, which is a harmful waste product of cells. This gas is dangerous when it builds up in the body. The blood carries carbon dioxide from the cells to the lungs, which get rid of the gas by exhaling. This process of exchanging gases is the essential function of the respiratory system.

6. During exercise
When you exercise, your body requires more oxygen than usual. The more you exercise, the less you will find yourself out of breath. This is because your lungs get used to taking in the required amount of oxygen efficiently. A trained athlete has a high lung capacity. His or her lungs have been trained to transport oxygen into the body with ease.

9. Interesting facts about the respiratory system
Hairs in the nose help to clean the air we breathe as well as warming it.
The capillaries in the lungs would extend 1,600 kilometres if placed end to end.
A person at rest usually breathes between 12 and 15 times a minute.
 The lungs contain structures like balloons, known as alveoli. There are an amazing 300 million of them in your lungs.

10. Activities On page 50 of the text book Label the diagram
Answer questions 1-5