The respiratory portion in the lungs is composed of which structures?

• A. Alveoli
• B. Larynx
• C. Trachea
• D. Bronchi

Answer: (A)

Verified step by step guidance

1. Understand the structure of the respiratory system: The respiratory system is divided into the conducting portion and the respiratory portion. The conducting portion includes structures that transport air to the lungs, while the respiratory portion is where gas exchange occurs.
2. Identify the structures involved in the conducting portion: The conducting portion includes the nasal cavity, pharynx, larynx, trachea, bronchi, and bronchioles. These structures are responsible for filtering, warming, and humidifying the air before it reaches the lungs.
3. Focus on the respiratory portion: The respiratory portion is specifically involved in the exchange of gases (oxygen and carbon dioxide) between the air and the blood. This is where the actual process of respiration takes place.
4. Recognize the key structure in the respiratory portion: The alveoli are the primary structures in the respiratory portion of the lungs. They are tiny air sacs where the exchange of gases occurs. The walls of the alveoli are thin and surrounded by capillaries to facilitate efficient gas exchange.
5. Differentiate between the options: Among the given options, only the alveoli are part of the respiratory portion. The larynx, trachea, and bronchi are part of the conducting portion, responsible for air passage but not directly involved in gas exchange.