The functions of the respiratory system are (Select all that apply)

- Gas exchange: The respiratory system is responsible for the exchange of oxygen and carbon dioxide between the atmosphere and the blood.

- Breathing: Also known as ventilation, this is the process of inhaling and exhaling air.
- Filter and humidify air: The respiratory system helps filter impurities and foreign particles present in the inhaled air. It also adds moisture to the air to prevent drying of the delicate lung tissues.
- Regulation of blood pH: By adjusting the levels of carbon dioxide in the body through breathing, the respiratory system helps maintain the acid-base balance of the blood.
- Phonation: The respiratory system plays a role in producing sound through the vocal cords, allowing speech and vocalization.
- Olfaction: The respiratory system provides a pathway for the sense of smell, as inhaled air carries odor molecules to the olfactory receptors in the nose.
- Immune defense: Certain cells in the respiratory system trap and remove pathogens and other harmful substances to help protect the body from infections.