You might be surprised by how small the uterus is (left). The fallopian tubes reach out to the ovaries, and the uterus—"a small and elegant structure," says Dr. Oz—stretches to hold a fetus.
Humans are the only mammals without a bone in their penises (right). This is because when men are sexually aroused, blood flows into the penis to make it stiff. That's another reason that men should exercise and eat well; doing so will keep the blood flowing throughout the entire body.