The tunica mucosa is a single-layer of epitheliurn which is composed of two types of cells, columnar or cuboical cells and mucous cells, the latter locates only in caecum, intestine and rectum.

• 粘膜层为单层上皮，由柱状或立方细胞组成，在胃盲囊、肠和直肠还含有粘液细胞。