  During growth, tissue expands and deforms. Given its elastic properties,
stresses emerge in an expanding and deforming tissue. Cell rearrangements can
dissipate these stresses and numerous experiments confirm the viscoelastic
properties of tissues [1]-[4]. On long time scales, as characteristic for many
developmental processes, tissue is therefore typically represented as a liquid,
viscous material and is then described by the Stokes equation [5]-[7]. On short
time scales, however, tissues have mainly elastic properties. In discrete
cell-based tissue models, the elastic tissue properties are realized by springs
between cell vertices [8], [9]. In this article, we adopt a macroscale
perspective of tissue and consider it as homogeneous material. Therefore, we
may use the "Structural Mechanics" module in COMSOL Multiphysics in order to
model the viscoelastic behavior of tissue. Concretely, we consider two
examples: first, we aim at numerically reproducing published [10] analytical
results for the sea urchin blastula. Afterwards, we numerically solve a
continuum mechanics model for the compression and relaxation experiments
presented in [4].
