Sexual characteristics

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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 two sexes of a species, but which are not directly part of the reproductive system.

Humans

Main article: Sex differences in 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:

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 clitoris, 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.

See also

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