Picture of Penis
The penis is part of the male urogenital tract, and it is also a sexual reproduction organ. The head of the penis, the glans, is covered by the foreskin (prepuce) in uncircumcised males. The corpus cavernosum is made of two long pieces of erectile tissue that run the length of the penis. The corpus spongiosum is spongy tissue that surrounds the urethra. Both the corpus cavernosum and corpus spongiosum fill with blood during sexual arousal to produce an erection. Blood flow into the penis that allows for erections is controlled by special nerves that respond to arousal signals. The urethra is the hollow tube that runs the length of the penis. It serves as an outlet for urine and semen to leave the body.
Text Reference: "Male External Genitalia." Clinical Anatomy: An Illustrated Review with Questions and Explanations.