An erection is a physiological phenomenon during which the penis lengthens, becomes engorged and firm. This phenomenon is often linked to sexual arousal, whereby the penis stiffens during sexual arousal or stimulation. Having an erection, however, does not always occur as a result of sexual arousal. In some cases, they can be spontaneous or occur during sleep.
More About Erection
Erection is compulsory to achieve sexual intercourse. In some cases, the scrotum also tightens while the man is erect. If the man is uncircumcised, the foreskin also pulls back during erection to reveal the penile glans. An erection can also be achieved through erotic fantasies, memories, sounds, touches and sights. Physically-speaking, the penis elongates because of the sudden flow of blood to the genital area.
In some cases, the man may not be able to attain erection. This condition is known as erectile dysfunction and can happen for a number of reasons. In such cases, medication or sex therapy might help the man reach an erect state again.