sentence: Ejaculation can also happen without control when a man is sleeping.
sentences_before: When a man is stimulated, his penis becomes erect. When he has an orgasm, semen comes out from the end of his penis. Semen contains sperm and other substances. How long a man can be stimulated before ejaculating, how long the ejaculation lasts, the strength of the ejaculation, and the amount of semen that comes out, all vary from one man to another.
sentences_after: Boys do not ejaculate until they reach puberty.
concept_name: ejaculation
headings: Ejaculation
categories: Female reproductive system Male reproductive system