MICROANATOMY

Detailed explanation-1: -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. Some insects such as grasshoppers have air sacs in their trachea system.

Detailed explanation-2: -Thickness of the alveolar membrane: The thinner the membrane, the faster the rate of diffusion of gases. Conversely, a thick membrane reduces the diffusion rate of gases across the alveolar membrane. Surface area: A large surface area increases the diffusion rate of gases across the membrane.

Detailed explanation-3: -A respiratory surface is covered with thin, moist epithelial cells that allow oxygen and carbon dioxide to exchange. Those gases can only cross cell membranes when they are dissolved in water or an aqueous solution, thus respiratory surfaces must be moist.

Detailed explanation-4: -Thin lining: the lining of the alveoli is very thin so that gases can quickly diffuse through it. Large surface area: human lungs contain about 500 million alveoli, which creates a surface area around half the size of a tennis court. This speeds up diffusion because gases have more area over which to diffuse.

Detailed explanation-5: -The tracheoles end within the body cells. Gases move by diffusion within the tracheal system. When the insect is less active the ends of the tracheoles contain fluid. It is where the fluid and gas meet (= the fluid/gas interface), that exchange of gases occurs (oxygen is taken up, carbon dioxide is given off).