The two functions of the respiratory system are as follows:

1. It provides oxygen to our cells that are needed for them to survive and function properly (cellular metabolism).
2. It eradicates carbon dioxide which is a waste product of the body.

The **upper region of the respiratory tract** specifically plays an important role in the filtration of foreign materials during the respiration process. However, when an individual engages in smoking tobacco, this region of the respiratory tract will be damaged and eventually lessen its effectiveness to protect the body.

Tobacco contains various substances that may negatively affect the body. Three of the known major substances are nicotine, carbon monoxide, and tar.

1. **Nicotine** – is a stimulant that causes an increase in heart rate and blood pressure.

2. **Carbon monoxide** – a type of poisonous gas that halts the transport of oxygen in the body. It binds with the hemoglobin molecule, thus decreasing the amount of oxygen present in the blood.

3. **Tar** – a substance that can cause or initiate cancer.

There are two types of respiration: External respiration and internal respiration.

**External respiration** is the process happening in the lungs where the exchange of gases happens between the atmosphere and the blood. On the other hand, **Internal respiration** is the process of the exchange of gases between the cells of the body and the blood.

**Breathing** is defined as the travel of air into and out of the lungs. It is an important function controlled by our nervous system, specifically our **medulla oblongata**. The autonomic nerves present in this organ and our diaphragm creates the contraction that regulates our breathing process.

At high altitudes, there is a lower atmospheric pressure. Because of this, the pressure inside the lungs is higher than the pressure outside the body. This makes it difficult for the oxygen to pass through the lungs, which increases the amount of carbon dioxide in the body. As a result, the body receives impulses from the breathing center, which are triggered by the high amount of carbon dioxide. These impulses tell us to breathe rapidly. This is the reason why a person starts to take in more breaths than the normal rate when they are at a high altitude.