The rigid state of the PENIS when it responds to sexual stimulus. An erection is necessary for eﬀective penetration of the VAGINA. As a result of sexual arousal, the three cylinders of erectile tissue in the penis become engorged with blood, lengthening, raising and hardening the penis. Muscles surrounding the blood vessels contract and retain the blood in the penis. Erections also occur during sleep and in young boys. Inability to have or maintain an erection is one cause of IMPOTENCE (see also SILDENAFIL CITRATE).
Article Categories:Medical Dictionary