Akademik Veri Yönetim Sistemi
Risk Factors and Therapy of Esophagus Cancer, Ömer Engin, Editör, Springer Nature, Zürich, ss.101-115, 2024
The esophagus, stomach, and colon are parts of the digestive tract formed as a hollow tube with a lumen of various diameters. The wall of this tube is composed of four layers: the mucosa, submucosa, muscularis externa, and serosa/adventitia. The mucosa of this tract consists of the epithelial layer, lamina propria, and muscularis mucosae. The submucosa consists of dense irregular connective tissue with blood vessels, lymphatics, and Meissner’s plexus of autonomic nerves. The muscularis externa generally consists of inner circularly, outer longitudinally arranged smooth muscle cells. Between the two sublayers of the muscularis externa, the myenteric (Auerbach) nerve plexus of autonomic neurons is found. The esophagus, stomach, and colon show histological differences in these four layers. For example, the esophagus consists of a nonkeratinized stratified squamous epithelium; however, the stomach and colon have a simple columnar epithelium. The stomach consists of well-developed tubular mucosal glands in the lamina propria, and the colon consists of intestinal mucosal glands in the lamina propria. The submucosal layer of the esophagus consists of mucus-secreting esophageal glands. The muscular layer of the esophagus and colon consists of the inner circular and outer longitudinal muscle layers. The muscular layer of the esophagus consists of striated muscle cells in the upper one-third, both striated and smooth muscle cells in the middle, and smooth muscle cells only in the lower third. However, the muscularis externa layer of the stomach consists of outer longitudinally, middle circularly, and inner obliquely arranged smooth muscle cells. The muscular layer of the colon has an outer longitudinal layer subdivided into three bands of smooth muscle called the taeniae coli. The stomach and the colon, except for the ascending and descending parts, are surrounded by the serosa covered by a simple squamous epithelium or mesothelium. The serosa of the esophagus above the diaphragm is replaced with the adventitia. This chapter is focused on the histological features of the esophagus, stomach, and colon.