Fine Structure of the Submucosal Layer of The Dog's Cervical Esophagus

Abstract

Six samples of cervical oesophagus were collected from apparently healthy adult dogs that died in different road accidents. The samples were processed for a transmission electron microscopy study. The submucosal layer of the canine esophagus consists of compound, muco-serous glands, fibroblasts, macrophages, plasma cells, lymphocytes, and connective tissue fibers, including collagen, reticular, and elastic fibers. The mucous acini displayed mucous and subsidiary cells with large lucent granules and small dense granules, respectively. The serous acinar cells had a nucleus, electron-dense granules of varying sizes and appearances, a Golgi apparatus, and abundant endoplasmic reticulum. The myoepithelial cells were flat, spindle-shaped, rich in tonofilaments, and rested on the basement membrane of the serous or mucous acini. The cells lining the duct ranged from low cuboidal cells to two-layered forms, becoming stratified at the opening into the lumen of the esophagus. The intra-lobar duct showed cells with prominent centrally located nuclei, electron-dense secretory granules, a greater number of mitochondria, polyribosomes, and endoplasmic reticulum. The plasma membrane of the cuboidal cells located towards the lumen of the duct showed blebs. The cells of the intralobar duct were joined to one another by desmosomes and tight junctions.