The majority of the surface is
covered by cuboidal and squamous pavement cells,
while basal undifferentiated cells contact the basal
lamina and intermediate undifferentiated cells fill
the intervening space. Notably, also within the
filament epithelium are numerous, large mitochondria-
rich cells and mucous cells (see below).
In contrast, the lamellar epithelium overlays the
arterioarterial circulation (Olson, 2002, this issue).
The epithelium is typically one to three cell
layers and composed of squamous pavement cells
and basal and intermediate non-differentiated
cells. Modified endothelial cells, called pillar cells,
support and define the lamellar blood spaces.