During sex, the penis becomes enlarged and erect to allow sexual intercourse. This erection occurs as a result of complex neurological, hormonal, vascular and psychological interactions, as the sensation of arousal causes a reaction in the brain, which sends nerve signals to the spinal cord and then to the penis.
The arteries that supply the body with blood expand as a reaction. The enlarged arteries increase blood inflation to these upright areas, which are filled with blood. Muscle contraction around veins that drain blood from the penis and reduce blood flow. Increased blood pressure in the penis causes increased penis length and size. Ejaculation occurs through the state of sexual arousal when friction occurs in the glands of the penis and there are other excretions that send signals to the brain and spinal cord. The nerves search the muscles for contractions through the channel of the epididymis, vessels carrying sperm, seminal vesicles and prostate. These contractions work on entering sperm into the urine stream. The contraction of the muscles around the urethra, in turn, takes the sperm out of the penis. The neck of the bladder also constricts to prevent the sperm from going back to the bladder. When ejaculation occurs, or the arousal stops, the arteries contract and the veins relax. This process reduces blood flow and makes the penis relax.
The arteries that supply the body with blood expand as a reaction. The enlarged arteries increase blood inflation to these upright areas, which are filled with blood. Muscle contraction around veins that drain blood from the penis and reduce blood flow. Increased blood pressure in the penis causes increased penis length and size. Ejaculation occurs through the state of sexual arousal when friction occurs in the glands of the penis and there are other excretions that send signals to the brain and spinal cord. The nerves search the muscles for contractions through the channel of the epididymis, vessels carrying sperm, seminal vesicles and prostate. These contractions work on entering sperm into the urine stream. The contraction of the muscles around the urethra, in turn, takes the sperm out of the penis. The neck of the bladder also constricts to prevent the sperm from going back to the bladder. When ejaculation occurs, or the arousal stops, the arteries contract and the veins relax. This process reduces blood flow and makes the penis relax.