The maintenance of a stable stem cell
population in the epidermis is important for robust regeneration
of the stratified epithelium. The population size is usually
regulated by cell secreted extracellular signalling molecules as
well as intracellular molecules. In this paper, a simple model
incorporating both levels of regulation is developed to examine
the balance between growth and differentiation for the stem cell
population. In particular, the dynamics of a known differentiation
regulator c-Myc, its threshold dependent differentiation, and
feedback regulation on maintaining a stable stem cell population
are investigated.