Service Areas and Surfactants

Mechanical and chemical properties of surfaces often interact to determine how liquids pass over or near surfaces. What adheres to an interface depends on how it adsorbs as well as upon the surface's elasticity and viscosity. Many parameters feed back controlling how dispersed and dilute or concentrated the bulk of the hemolymph becomes. Hemolymph composition fluctuates as matter passes from the hemolymph into the cells through surfaces and as new materials enter the hemolymph from the surfaces. However, such changes have not yet been studied. Curving of a surface creates localized regions of differing pressures in the hemolymph. Finally, capillary effects themselves may affect the global hydrodynamics for transfer, as the volumes of hemolymph and the wetting of surfaces change with an insect's hydration.

Surfactants stabilize the moving colloidal systems of films, drops, bubbles and foams. Stabilization alters systemic properties and can influence how devices work. Can learning about insect surfactants teach us how to improve our own? After all, volumes of insect surfactant must be quite small, so insect surfactants undoubtedly are very capable of influencing boundary conditions in extremely small systems that could have great practical importance for us. Surfactants also resist clotting in the bulk flow but may encourage clotting if hemolymph exudes from a cut in the cuticle. Hysteresis probably changes as a hemocoel changes shape. Hysteresis effects are common in lungs that change size on inspiration and expiration (Ref: Hysteresis).

Smooth or convoluted, surfaces of the hemocoel efficiently contact the hemolymph flowing over them. Molecules can be thought of as following a concentration gradient driving them in their directions of movement. When an organ accepts molecules through its walls, the molecule's concentration in the hemolymph decreases, unless of course, its supply from the midgut or other source keeps up with removal matching demand.

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