The root is located within the forward-facing region of the pelvis. It is composed of the corpora chambers, which divide in two to form the crura. In front, the root is anchored to the pubic bone. Most sensation within the penis is provided by the dorsal penile nerves, which is a branch of the internal pudendal nerves. The pudendal nerves also send signals to the muscles that control ejaculation - ejection of semen from the penis.
Erection occurs due to the action of specific nerves known as the nervi erigentes.
Blood flow within the penis primarily is provided by the cavernous arteries, branches of the penile artery. This network supplies blood to the erection-forming tissue of the penis. In men, the urethra is a tube that extends from the bladder to the end of the penis. It passes urine or semen out of the body. The urethra is approximately 8 to 9 inches in length and extends from the bladder neck to the end of the penis.