Human males typically possess an XY combination. Karyogram of human male using Giemsa staining. Trans men have a gender identity that does not align with their female sex assignment at birth, while intersex men may have sex characteristics that do not fit typical notions of male biology. Male anatomy is distinguished from female anatomy by the male reproductive system, which includes the penis, testicles, sperm duct, prostate gland and the epididymis, as well as secondary sex characteristics. These include greater muscle mass, the growth of facial hair and a lower body fat composition. During puberty, hormones which stimulate androgen production result in the development of secondary sexual characteristics, thus exhibiting greater differences between the sexes. Sex differentiation of the male fetus is governed by the SRY gene on the Y chromosome. Like most other male mammals, a man's genome usually inherits an X chromosome from the mother and a Y chromosome from the father. Prior to adulthood, a male human is referred to as a boy (a male child or adolescent).
