陰莖末端的一些皮膚形成遊歷懸掛的皺褶，就是大家熟知的包皮或陰莖包皮。這快包皮通常覆蓋著被稱為龜頭的陰莖頭。但是，在勃起的情況下，龜頭從包皮突出而且完全暴露。

Foreskin
Toward the end of the penis some of this skin forms a freely hanging fold known as the foreskin or prepuce. This foreskin normally covers the tip or head of the penis called the glans. In the case of an erection, however, the glans protrudes from the foreskin and becomes fully exposed.