  Lumen formation plays an essential role in the morphogenesis of tissues
during development. Here we review the physical principles that play a role in
the growth and coarsening of lumens. Solute pumping by the cell, hydraulic
flows driven by differences of osmotic and hydrostatic pressures, balance of
forces between extracellular fluids and cell-generated cytoskeletal forces, and
electro-osmotic effects have been implicated in determining the dynamics and
steady-state of lumens. We use the framework of linear irreversible
thermodynamics to discuss the relevant force, time and length scales involved
in these processes. We focus on order of magnitude estimates of physical
parameters controlling lumen formation and coarsening.
