Elastic reticulum and collagen of normal mouse peritoneum—A conventional and high-voltage electron microscopy study

The ultrastructural and three-dimensional arrangement of elastic reticulum and collagen in mouse parietal peritoneum is described for the first time. As seen by high-voltage electron microscope stereoscopy of thick sections, the EL forms a three-dimensional network without free ends. The central part of the EL fibre is not amorphous but contains irregular 500-100 nm fibrils along its length. Large bundles of banded collagen (also without free ends) course in and out of the elastic reticulum. The production of these two interlacing networks implies the presence of a histo-architectural sensing and orientation system for the projected cytoplasmic processes of stromal fibroblasts and also bidirectional chain assembly for both collagen and elastin. Bilaterial assembly patterns have been described for collagen but not for elastin.

The periodicity of the banded collagen varies in different regions of the fibre. A similar banding periodicity variation has been reported for Type I tendon collagen in association with local tension variations and curvature of the fibres.

An unbanded type of collagen (so far not characterized as to type) lies between the elastic reticulum and the mesothelial cell basal lamina. It is speculated that the banded collagen may play a role in control of transudate across peritoneum and its disorganization in inflammation may relate to affect ascites production.