Modern airplanes are built with waterproof seals around the windows and rivets are used to hold the metal sheets to the frame, forming the fuselage. The waterproof seals are to rivets as are to

tight junction; desmosomes

Explanation: Tight junctions are connected areas of the plasma. They form a water tight seal and acts as barrier against the movement of water, solute and prevents passage of materials between the cells or epithelial layers.

Desmosomes forms a strong connection that joins intermediate filament of adjacent cells, they can be viewed as rivets through the plasma membranes of adjacent cells.

answer; the changing age structure of the population;