Table 2. A brief summary of the main differences between the models and their behaviour, and how this compares to experimentally-observed behaviour of the crypt.

	2D Cylindrical Model	3D Model	2D Cross-Sectional Model	Experimental System
Cell dynamics	Off-lattice cell centre model			--
Cell-cell connectivity	Delaunay triangulation	Overlapping spheres	Delaunay triangulation	--
Geometry	A cylinder that is cut open and rolled out to form a 2D rectangular domain.	A rigid 3D test-tube shaped geometry.	A deformable 2D longitudinal cross-section through the crypt.	--
Cell cycle	Stochastic Wnt-dependent cell cycle model			--
Cell death	Cell sloughing is defined to occur above a threshold height.	Cell sloughing is defined to occur above a threshold height.	(i) Random cell sloughing at the crypt orifice and (ii) cell death after loss of contact with basement membrane.	Cells are sloughed towards the crypt orifice, and undergo apopotosis following extrusion from the epithelium.
Cell velocity	Increasing up the vertical axis, levelling out in differentiated compartment.	Increasing up the vertical axis towards the orifice.	Increasing up the vertical axis, before levelling out then decreasing on the intercrypt table.	Increases linearly moving up the crypt axis. Rate of increase slows on the villus.
Following elimination of cell division	Cell migration continues. Cell number decreases exponentially before plateauing. Crypt size unaffected (due to geometry).	Cell migration continues. Cell number decreases exponentially before plateauing. Crypt size unaffected (due to geometry).	Cell migration continues. Cell number decreases linearly. The crypt shrinks.	Cell migration continues, crypts shrink.