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Fig. 2. Propidium iodide staining demonstrates a mitotic cell (BC) in the
oesophageal interpapillary basal layer (IBL). Cellular division in the IBL is
rare and, as illustrated here, generally occurs at right angles to the
underlying basement membrane. This yields one daughter cell that remains in
the IBL and one that enters a zone of high proliferative activity (the
epibasal layers). Mitoses in the papillary basal layer (not shown) are
symmetrical, yielding two daughter cells that remain in contact with the
basement membrane.