Distribution of diaphragmatic lymphatic stomata

In seven anesthetized rabbits we measured the size, shape, and density of lymphatic stomata on the peritoneal and pleural sides of the diaphragm. The diaphragm was fixed in situ and processed for scanning electron microscopy. Results are from 2,902 peritoneal and 3,086 pleural fields (each 1,620 μm²) randomly chosen from the various specimens. Stomata were seen in 9% of the fields examined, and in 30% of the cases they appeared grouped in clusters with 2-14 stomata/field. Stoma density was 250 ± 242 and 72 ± 57 (SD) stomata/mm² on peritoneal and pleural sides, respectively, and it was similar over the muscular and tendinous portion of the two surfaces. The maximum diameter ranged from 2, respectively. The maximum and minimum diameter and surface area values followed a lognormal frequency distribution, suggesting that stomata geometry is affected by diaphragmatic tension.