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Fig. 1. Basic structure of the human oesophageal epithelium. H&E staining (top
image) shows the normal stratified squamous epithelium of the human
oesophagus. Invaginations of the basement membrane produce characteristic tall
papillary structures (P) at regular intervals. The schematic representation
(lower image) demonstrates the complexity of the epithelium. The epithelium is
divisible into two zones, a differentiated zone (yellow) consisting of
progressively flattened terminally differentiated keratinocytes and a
generative basal zone. The latter zone is complex, and three cellular
compartments can be identified. The single layer of cells directly adherent to
the basement membrane (the basal layer) is divisible into two components: the
flat interpapillary basal layer (IBL, red) and the papillary basal layer (PBL,
green). Above the basal layer there are multiple layers of basophilic cells
that have initiated the squamous differentiation program but are still capable
of dividing (the epibasal layers, gray). The schematic is not drawn to scale.
In vivo, the differentiated layer (yellow) is approximately 20 to 24 cell
layers deep. In normal subjects the length of the papillae and basal zone
thickness are said to be less than 66% and 10% of the total thickness of the
epithelium, respectively (Geboes and
Desmet, 1978 ; Ismail-Beigi et
al., 1970). The relative thickness of the differentiated zone and
basal zone varies along the oesophagus and between individuals (see text)
(Ismail-Beigi et al., 1970;
Behar and Sheahan, 1975).
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