What is the purpose of the trachea in animals?

The trachea plays a vital role in the respiratory system of animals. It is a tube that functions as a passageway for air to travel between the larynx and the lungs. This allows for the intake of oxygen from the environment and the expulsion of carbon dioxide. The trachea is structured to maintain open airflow, lined with cilia and mucus that help filter and humidify the air before it reaches the lungs, ensuring that the respiratory system operates efficiently.

The other options do not pertain to the primary function of the trachea. Unlike a digestive organ, the trachea does not assist in breaking down food. It also does not serve to protect the brain, which is the function of the skull and meninges. Lastly, the trachea is not a component of the circulatory system; it is exclusively part of the respiratory system, involved in gas exchange rather than the transport of blood.