Which of the following is NOT one of the three layers of the conducting zone?

• A. Mucosa
• B. Submucosa
• C. Alveolar layer
• D. Adventitia/cartilage

Answer: (C)

The conducting zone of the respiratory system consists of the structures that facilitate the passage of air to the lungs but do not participate in gas exchange. This zone includes the trachea, bronchi, and bronchioles. It features three primary layers: the mucosa, submucosa, and adventitia/cartilage.

The mucosa is the innermost layer, lined with epithelial cells, which play a key role in protecting the airways and facilitating secretion. The submucosa contains connective tissue, blood vessels, and glands, helping to support the mucosa and providing the necessary moisture and mucus for air movement. The adventitia/cartilage surrounds the conducting airways and provides structural support to prevent collapse during respiration.

The alveolar layer, in contrast, is found in the respiratory zone of the lungs, specifically in the alveoli where gas exchange occurs. Since the question asks for a layer not associated with the conducting zone, the alveolar layer is the correct choice, as it serves a distinct function separate from the primary roles of the conducting zone. Thus, understanding the structure and function of these layers is crucial for comprehending pulmonary physiology.