Sexual characteristics
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.
Humans
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:
- estrogens
- progesterone
- androgens such as testosterone
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 gonads | ovaries | testes |
| 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 external genitalia |
glans clitoridis, labia, vulva, clitoral hood perineal urethra |
glans penis, scrotum, phallus, foreskin fused perineum |
| Secondary sexual characteristics (Sex) | ||
| Usually | Breasts, menstrual cycle, development of "hourglass" body form, relatively shorter height, relatively more body fat | Facial and body hair, development of "triangular" body form, relatively higher height, relatively less body fat |
| Usually both sexes | Pubic hair, underarm hair | |
Humans whose sexual characteristics are ambiguous or mismatched are called intersex.
Invertebrates and plants
In invertebrates and plants, hermaphrodites (which have both male and female sexual characteristics either at the same time or during their life cycle) are common, and in many cases, the norm.
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.