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Asthma is a condition of the respiratory system, which is what we as humans use to breathe. When we breathe in, we are inhaling oxygen into our lungs, and when we exhale, we are breathing out carbon dioxide. Breathing is essential for humans, and should even one part of the respiratory system gets blocked or fail, the consequences could be devastating. Now we will look more in-depth into the actual anatomy of the respiratory system.

When we breathe in, air enters through either the mouth or the nose into the airway and goes down the throat into the pharynx. Here, the pharynx splits into two parts, the oesophagus and the larynx. The oesophagus is the tube which connects the throat to the rest of the digestive system, whereas the larynx continues on the airway. After leaving the larynx, the air enters the trachea, which takes the air down into the chest. Here, the trachea splits into two bronchi. Each bronchus takes the air into the lungs, where it branches off into lots of bronchioles.

At the end of each bronchiole is an air-filled sac called an alveolus. Each healthy, adult lung contains on average around 300 million alveoli, and this is the site where gas exchange takes place. Within each of the alveoli, oxygen in the inhaled air moves into the bloodstream. Meanwhile, CO2 gas diffuses out of the bloodstream, back into the lungs, ready to be exhaled. When exhaling, the now carbon dioxide-rich air leaves back up through the airway and out of the mouth or nose.

Below the lungs, there is a muscle called the diaphragm which helps pull air in and push air out when we breathe. Interestingly, it is the uncontrollable contraction of this muscle which causes hiccups. Other muscles involved in the respiratory system are the external and internal intercostal muscles.