乳腺導管(duct of mammary gland)

1.小葉內管(Intralobular duct)：與腺泡同為單層立方上皮(simple cuboidal epithelium)；外有肌上皮細胞
2.小葉間管(Interlobular duct)：單層柱狀上皮(simple columnar epithelium)
3.輸乳管(Lactiferous duct)：
A.共有10~20支，開口於乳頭；在乳頭附近會膨大，改稱為輸乳竇(lactiferous sinus)
B.為重層立方上皮(stratified cuboidal epithelium)；但於開口處會轉變為重層扁平上皮(stratified squamous epithelium)；甚至在靠近乳頭處還會轉變為角化的重層扁平上皮(keratinized stratified squamous epithelium)
＊在泌乳期(lactation phase)時，小葉內管、腺泡(alveoli)的腔內均有乳汁，且都有肌上皮細胞，兩者不好區分