Simplify the following text for a Grade 8 native English-speaking person.
Original: The corpus cavernosum penis is one of a pair of sponge-like regions of erectile tissue which contain most of the blood in the penis during penile erection .
Simplified: The corpus cavernosum penis ( or corpus cavernosum urethrae ) is one of two sponge-like sections of tissue in the male penis . They contain most of the blood during an erection .