To learn more about erectile dysfunction (ED), it is important to understand how the penis works normally. The normal erection process includes the following five stages:
Stage 1: Initial Filling—With psychological or sexual stimulation, neurotransmitters cause penile smooth muscles to relax, increasing blood flow to the corporal bodies.
Stage 2: Partial Erection (Tumescence)—Increased blood flow elongates and expands the penis. Penile arteries expand to accommodate the increased blood flow needed to elongate and expand the penis.
Stage 3: Full Erection—The increased volume of blood within the penis is prevented from draining, thus expanding the penis to full erection.
Stage 4: Rigid Erection—Maximum rigidity is attained. The glans and spongiosum (body and tip of the penis) enlarge until penile veins are forcefully compressed. This increases engorgement and maintains maximum penile rigidity. Emission of semen and ejaculation occur.
Stage 5: Return to Flaccidity (Detumescence)—Muscle contractions result in increased blood outflow from the penis, thus decreasing its length and girth until flaccid.
Problems can occur during any of the first four stages of erection that prevent you from either achieving or maintaining an erection. Although difficulties also can happen during the fifth stage (detumescence), they are not generally included in discussions of ED. |
