small intestine diagram. cross-section of a typical segment of the intestinal wall showing the layers: mucosa, submucosa

gastrointestinal system anatomy small intestine diagram typical segment intestinal wall showing layer mucosa submucosa muscularis serosa gut structure internal epithelial health anatomical villus celiac human illustration mucous epithelium lamina propria mucosae gland duct circular muscle longitudinal connective tissue peritoneum nerve mesentery blood vessels lumph nodule