sentence: Boys begin making sperm when they start growing into men, at a time of life called puberty.
sentences_before: As well as being chemical-producing glands, testicles are gonads. Apart from 'hormones', the other important substances made by the testicles are spermatozoa, which are generally just called sperm. Scientists call making sperm 'spermatogenesis'.
concept_name: boy
headings: Testicle Function Making sperm
categories: Anatomy of the male reproductive system Glands