The epithelium consists of high columnar cells, basophil gland cells and granule gland cells.The connective tissue is filled with fibers, blood tubes and nerves.

• 上、下表皮细胞可分为高柱状细胞、弱嗜碱性腺细胞和颗粒状腺细胞3种，结缔组织中富含纤维、血管和神经。