THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -Four characteristics of an efficient respiratory surface are: thin epithelium, large surface area, abundant capillaries, ventilation mechanism.

Detailed explanation-2: -Tracheoles have thin and moist walls to increase the efficiency of gaseous exchange. The large number of tracheoles also provides a large surface area to facilitate gaseous exchange through diffusion directly into the cells.

Detailed explanation-3: -Answer: The characteristics of a respiratory surface are thin walls, a moist inner surface, a huge combined surface area, a rich blood supply each alveolus is sounded by capillaries. Surfaces which dries out easily, thick and easily damaged are not a characteristic of good respiratory surface.