Question

multiple choice question
the respiratory membrane is the thin wall between the alveolar lumen and the

o alveolar duct
o respiratory bronchiole
o blood
o lymph

Explanation:

The respiratory membrane is crucial for gas exchange. It consists of the alveolar epithelium, capillary endothelium, and their fused basement membranes. Gas exchange occurs between the alveolar lumen (where air is) and the blood in the pulmonary capillaries. The alveolar duct and respiratory bronchiole are parts of the airway system and not directly involved in the gas - exchange interface of the respiratory membrane. Lymph is not part of the immediate gas - exchange structure at the respiratory membrane.

Answer:

blood