Illustration copyright 2002 by Nucleus
Communications, Inc. All rights reserved.
When a man becomes aroused, his brain sends nerve impulses that
increase blood flow to his penis. The blood fills the spongy chambers (corpora
cavernosa) in the penis, causing it to expand and become rigid. The veins that
would normally drain blood from the penis constrict, trapping the blood inside
and maintaining the erection.
After ejaculation or when the man is no longer sexually aroused, the
arteries narrow, the veins expand, and the blood drains out of the penis. The
penis returns to its normal size and is no longer rigid.
How this information was developed to help you make better health decisions.