ABSTRACT
The average adult human body is composed of over 60% water by mass (64), while various tissues in the body such as the striated muscle, lungs, kidney, and spleen are composed of more than 75% water, with a majority of that water being stored within the cells and surrounding extracellular matrix (ECM) (64). Blood is another tissue that is predominantly water, with over 90% of blood plasma being composed of water. With fluids making up such a large portion of the human body, it is important to understand how they behave under various physiological and diseased conditions, 554and how that behavior can influence the local environment of the body on a micro and macro level. In mechanics, fluids are defined by their ability to continuously deform under the application of shear stress, and are therefore studied under two distinct mechanical states, dynamic and static. Fluid deformation results in fluid flow, generating fluid shear stress on the surface of an object it is in contact with. Extensive investigation into the effects of fluid shear stress on cells such as vascular endothelial cells (19,100), renal tubular epithelial cells (22,47), various stem cells and progenitor cells (52,74,108), and osteocytes (26,51,106) has been conducted. While significant strides are being made to understand the importance of fluid dynamics (i.e., fluid shear stress) on cell mechanobiology, there has been less investigation into the effects of fluid statics. In the past decade, however, it has been recognized that various cell types, such as those in connective tissue (chondrocytes and osteocytes), epithelial cells, nervous system (neurons and retinal ganglion cells), and muscle cells are exposed to fluid statics in the form of hydrostatic pressure.
