Which organ is part of the upper division of the respiratory system?

The nose is considered a part of the upper division of the respiratory system because it serves key functions in the initial stages of respiratory processes. It is responsible for filtering, warming, and humidifying the air we breathe before it moves deeper into the respiratory tract. The structure of the nose includes nasal passages that allow for airflow and the presence of mucous membranes and cilia that help trap particles and pathogens.

In contrast, other structures like the trachea, lungs, and bronchial tree belong to the lower respiratory tract. The trachea acts as a main airway leading to the lungs, while the lungs themselves are the primary organs of gas exchange. The bronchial tree, which branches out from the trachea into smaller bronchi and bronchioles, conducts air into the lungs. Thus, these components are categorized as part of the lower respiratory system due to their involvement in air conduction and gas exchange rather than the initial processes of inhalation and filtration that occur in the nose.