A SCANNING ELECTRON-MICROSCOPY STUDY OF PERITONEAL STOMATA IN DIFFERENT PERITONEAL REGIONS

Peritoneal stomata constitute the pathways for the drainage of intrape ritoneal contents from the peritoneal cavity to the lymphatic system a nd have been claimed to be exclusively restricted to the peritoneal su rface of the diaphragm. This concept has been revised by the demonstra tion of peritoneal stomata in the omental, mesenteric, ovaric and pelv ic peritoneum. Therefore, the aim of this study was to further assess peritoneal surfaces of several other abdominal organs and of the abdom inal wall with special reference to the occurrence of peritoneal stoma ta. The peritoneum covering the spleen, stomach, intestine, liver, dia phragm and anterior abdominal wall obtained from rats was examined by scanning electron microscopy. Whereas the splenic and hepatic peritone al surfaces were composed of uniformly distributed cuboidal mesothelia l cells, the gastric and intestinal peritoneal surfaces were arranged in parallel folds composed of prominent mesothelial cells with elongat ed finger-like cytoplasmic processes. In addition to diaphragmatic per itoneal stomata, mesothelial openings were also found on the peritonea l surfaces covering the anterior abdominal wall and the liver. The par ietal peritoneal stomata were arranged in clusters, oval in shape and delimited by flattened mesothelial cells exposing the underlying subme sothelial connective tissue. The hepatic mesothelial openings formed b y deep channel-like gaps of adjacent cuboidal mesothelial cells were a lmost completely occluded by a dense microvillous coat. As the submeso thelial connective tissue was not identifiable with certainty, the mes othelial openings were regarded as corresponding to stoma-like structu res. These findings yield further evidence that peritoneal stomata are obviously not confined to the diaphragmatic area but extend to other peritoneal regions. It is therefore suggested that these extra-diaphra gmatic parietal and visceral peritoneal surfaces contribute to the abs orption capacity of the entire peritoneum and are subsequently involve d in either therapeutic procedures or pathological processes affecting the peritoneal cavity.