The terminal hindgut forms the upper portion of the anal canal . 末端后肠形成肛管的上部。
2.
Hemorrhoids comprise of clusters of small blood vessels and connective tissues in the anal canal 痔疮是由肛门的细小血管和结缔组织形成，它可分为内痔及外痔。
3.
Orthotopic anal reconstruction through partial excision of sphincter and anal canal reforming with smooth muscle 括约肌部分切除加平滑肌肛管成形原位肛门再造术
4.
Fucking without a condom and pulling out before you cum is also extremely unsafe as both semen and pre - cum can carry hiv and the virus can easily enter the bloodstream through the membranes lining the anal canal 不带套就提枪上阵，就算不射也是极端危险的，因为精液和前列腺液都可能携带hiv ，病毒要穿透菊花内部的表皮细胞简直轻而易举。
