Which of the following structures is part of the upper respiratory system?

• A. Trachea
• B. Alveoli
• C. Bronchi
• D. Nasal cavity

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the division of the respiratory system into two main parts: the upper respiratory system and the lower respiratory system. The upper respiratory system includes structures involved in air intake and initial filtration, while the lower respiratory system is responsible for gas exchange and air conduction deeper into the lungs.
2. Step 2: Identify the structures listed in the problem and classify them based on their location and function. The trachea, alveoli, and bronchi are part of the lower respiratory system, while the nasal cavity is part of the upper respiratory system.
3. Step 3: Recall the anatomical features of the nasal cavity. It is located in the upper respiratory system and serves as the primary entry point for air. It filters, warms, and humidifies the air before it moves to the lower respiratory structures.
4. Step 4: Compare the nasal cavity to the other structures listed. The trachea is a tube that connects the larynx to the bronchi and is part of the lower respiratory system. The alveoli are tiny air sacs in the lungs where gas exchange occurs, and the bronchi are airways that branch from the trachea into the lungs, both of which are also part of the lower respiratory system.
5. Step 5: Conclude that the nasal cavity is the correct answer because it is the only structure listed that belongs to the upper respiratory system.