Which parts of the respiratory system are classified as the upper respiratory tract?

The upper respiratory tract is specifically defined as the region of the respiratory system that includes structures involved in air intake and filtration prior to the air reaching the lungs. The nasal cavity, pharynx, and larynx play crucial roles in warming, humidifying, and filtering the air we breathe.

The nasal cavity is the first part where air enters, equipped with mucous membranes that trap particles and pathogens. The air then passes through the pharynx, which acts as a pathway to both the respiratory and digestive systems, facilitating the passing of air into the larynx. The larynx, often referred to as the voice box, is significant not only for its role in sound production but also for directing air from the pharynx down towards the lower respiratory tract.

In contrast, the other options pertain to parts of the respiratory system that are categorized within the lower and terminal regions. The trachea and primary bronchi make up the branching airways entering the lungs, while the alveoli are the tiny air sacs where gas exchange occurs, and the bronchioles are the smaller branches leading to alveoli. The diaphragm, meanwhile, is a muscle crucial for breathing but does not fall within the upper respiratory tract.