The penis supports the |urethra| as it passes from the |seminal vesicles|, through the corpus cavernosa, to the ~meatus~ (opening) at the glans (head) of the penis. The corpus cavernosa are made of spongy tissue which fill with ~blood~ during sexual arousal. As the ~blood~ fills these tissues, the penis begins to expand and become firm, and this condition is known as an erection. The erection facilitates the ejaculational transport of the ~semen~ to the female's |vagina|.
