Sexual characteristics are physical or behavioral traits of an organism (typically of a sexually dimorphic organism) which are indicative of its biological sex. These can include sex organs used for reproduction and secondary sex characteristics which distinguish the sexes of a species, but which are not directly part of the reproductive system.
In humans, sex organs or primary sexual characteristics, which are those a person is born with, can be distinguished from secondary sex characteristics, which develop later in life, usually during puberty. The development of both is controlled by sex hormones produced by the body after the initial fetal stage where the presence or absence of the Y-chromosome and/or the SRY gene determine development.
Hormones that express sexual differentiation in humans include:
Typical sexual characteristics
The following table lists the widely accepted sexual characteristics in humans:
|Level of definition||Female||Male|
|Biological levels (Sex)|
|Primary sexual characteristics (Sex)|
|Usual sex chromosomes||XX in humans||XY in humans|
|Usual level of sex hormones||oestrogen, gestagen||testosterone|
|Usual anatomy of internal genitalia||clitoral crura, vagina, uterus, fallopian tubes||corpora cavernosa, urethra, prostate, seminal vesicles|
|Usual anatomy of
|glans clitoridis, labia, vulva, clitoral hood
|glans penis, scrotum, phallus, foreskin|
|Secondary sexual characteristics (Sex)|
|Usually||females have larger breasts, menstrual cycle, development of "hourglass" body form, relatively shorter height, relatively more body fat, 10 to 12% less lung capacity, smaller heart||Facial and body hair, development of "triangular" body form, relatively higher height, relatively less body fat|
|Usually both sexes||Pubic hair, underarm hair|
Humans born with sex characteristics that are in any way from both columns are called intersex, being a natural human variation.
Invertebrates and plants
In other varieties of multicellular life (e.g. the fungi division, Basidiomycota) sexual characteristics can be much more complex, and may involve many more than two sexes. For details on the sexual characteristics of fungi, see: Hypha and Plasmogamy.
- Bellemare F, Jeanneret A, Couture J (2003). "Sex differences in thoracic dimensions and configuration". Am J Respir Crit Care Med. 168: 305–12. doi:10.1164/rccm.200208-876OC. PMID 12773331.
- Glucksman A (1981). Sexual Dimorphism in Human and Mammalian Biology and Pathology. Academic Press. pp. 66–75.