Biology Reference
In-Depth Information
FIGURE 20.14
The division of a vessel lumen by fusion of infolding walls. The reality is seldom as geomet-
rically simple as this diagram (see main text).
The topology of infolding endothelium ensures that the apical sides of the endothelial cells
always face the blood. As the folds form, they carry in with them the extracellular matrix that
is associated with their basal surfaces, especially collagen, and they can also carry in with
them 'endothelial-like' cells that are closely associated with the outsides of vessel walls.
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Where folds completely cross the vessel, the space between the basal surfaces of the endothe-
lial cells can be invaded by cells of the surrounding tissue so that the tissue effectively flows
into the new 'space' between the two halves of what was once a single vessel. Where folds
will form just a pillar, the processes of endothelial-like cells that are trapped within the pillar
organize the collagen there so that its fibrils form mechanically strong bundles. The cells and
the collagen remain in the pillar core when it is cut off by disappearance of the base of the fold
itself (
Figure 20.15
).
FIGURE 20.15
The role of endothelial-like cells, shown in orange, in the organization of collagen during
formation of intralumenal pillars. This diagram is based on the discussion of Patan et al.
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