The effect of age and sex on the esophageal wall structure in dogs

The aim of this project was to study the influence of the sex and age factors on the wall structure of the esophagus of the dog. Eighteen mixed breed dogs, (9 male and 9 female) in three age groups (3 neonate, 3 sexually mature and 3 old) were used. Animals were euthanized and after removing the whole esophagus, full thickness transverse sections were cut from the proximal, middle and distal parts. Microscopic sections of these samples were prepared and then examined for minimum and maximum thicknesses of the tunicae mucosa, submucosa and muscularis. Due to the absence of lamina muscularis mucosa in the proximal part of canine esophagus, the tunicae mucosa and submucosa in this region were collectively named tunica mucosa-submucosa. Results obtained from this study showed that there is a large increase in the thickness of tunica mucosa-submucosa and mucosa, from neonatal to sexually mature stages followed by a smaller increase between sexually mature and old stages in both sexes. We also found that the thickness of the mucosal layer is greater in distal part of esophagus than its middle part in all three age groups and both sexes. The thickness of tunica submucosa of the middle and distal parts and tunica muscularis of the proximal, middle and distal parts of esophagus showed a large increase between neonatal and sexually mature stages followed by a smaller decrease between sexually mature and old stages in both sexes. Also we found that the thickness of the submucosal layer is greater in distal part of esophagus than its middle part in all three age groups and both sexes. The thickness of the muscular layer showed a progressive increase from proximal part to the distal part in all age groups and both sexes. The differences between two sexes in the thickness of esophageal layers do not follow a constant pattern.