translation.en: It has a central space of spongy erectile tissue that fills with fluid -- in this case blood -- surrounded by a wall of tissue that's rich in a stiff structural protein called collagen.
translation.zh: 它中间空间的 海绵状勃起组织 里面充满了液体——在这种情况下是血液—— 周围被富含胶原蛋白的组织包裹 胶原蛋白是一种不易弯曲的结构蛋白