No exchange of gases occurs here. 2. : Secrete a fluid containing surfactant. 3. : Where the respiratory zone of the lungs begins. 4. : Form a simple squamous epithelium in the alveoli. 5. : Terminates in alveoli. 6. : Are cuboidal cells. 7. The respiratory membrane consists of 3 layers: capillary endothelium, fused basement membrane and alveolar epithelium consisting of .

There is a specific path way for the whole exchange system of the human body and other animal's body. As the exchange of the gaseous system starts over from the start of the lungs or alveolis (the small sacs present inside the lungs) towards the blood stream inside the circulation system of the body. And here is the region for the initiation of the respiratory zone of the lungs begins and ends up in the bloodstream back towards the lungs of the human body.         The respiratory membrane consists of 3 layers: capillary endothelium, fused basement membrane and alveolar epithelium consisting of small air spaces or alveolas.                                                            

C. a mature ovule of a plant.