Erection - Definition

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Definition


An erection is the physiological phenomenon in which the male sexual organ enlarges and hardens due to increased blood flow to its vessels. It is a natural function that serves a role in mating, and is generally associated with sexual arousal. This arousal sends signals of stimulation from the brain to the penis, passing through the nervous system (spinal cord and erector nerves). An erection may also occur without any sexual stimuli (nocturnal erections, for example).