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MCAT Content / Respiratory System / General Function

General function

Topic: Respiratory System

The general functions of the respiratory system are the exchange of gases, thermoregulation, and filtering materials coming into the lungs from inhaled air.

The air that is inhaled in the body contains oxygen. When this air reaches the alveoli, oxygen is exchanged into the blood and carbon dioxide exchanged out of the blood. Thus, lungs help in the exchange of gases. Oxygen is then transported around the body via red blood cells and the circulatory system to respiring tissue, in the same process removing waste carbon dioxide back to the lungs.

The respiratory system also functions to regulate the temperature of the body through thermoregulation. When air is exhaled from the lungs, heat is also lost in the form of moist air reducing the temperature of the body.

The nostrils have hair whilst the respiratory tract has cilia and mucus lining. These features help to filter the particles present in the inhaled air. These trap pathogens and other bigger harmful particles, preventing their entry in the lungs. This is also the case for small particulate matter, particularly pollutant particles which can enter the respiratory system.


Key Points

• The respiratory system helps in the exchange of oxygen and carbon dioxide between the environment and the blood circulation.

• The respiratory system helps in thermoregulation by exhaling moist air.

• The respiratory system protects from pathogens and foreign particles that come in the inhale air by trapping them by the hairs in the nostril, and mucous lining and cilia of the respiratory tract wall.


Key Terms

mucus: a lining in the walls of the organs that secrete sticky mucous secretions that trap particles

alveoli: small, grape-like sac that performs gas exchange in the lungs

circulatory system: the name given to the system of heart, vessels and blood transporting substances around the body

thermoregulation: homeostatic control of the bodies temperature

cilia: small hair-like protrusions that catch dirt and bacteria in the air

pathogens: microorganisms that cause harm to host organisms



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