A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction
. The reproductive organs together constitute the reproductive system
. In animals, the testis
in the male, and the ovary
in the female, are called the ''primary sex organs''.
All others are called ''secondary sex organs'', divided between the external sex organs—the genitals or genitalia, visible at birth in both sexes—and the internal sex organs.
s, and some similar plants have gametangia
for reproductive organs, which are part of the gametophyte
. The flower
s of flowering plant
s produce pollen
and egg cell
s, but the sex organs themselves are inside the gametophytes within the pollen and the ovule
. Coniferous plants
likewise produce their sexually reproductive structures within the gametophytes contained within the cones
and pollen. The cones and pollen are not themselves sexual organs.
The ''primary sex organs'' are the gonad
s, a pair of sex organs, which diverge into testes
following male development or into ovaries
following female development. As primary sex organs, gonads generate reproductive gamete
s containing inheritable DNA
. They also produce most of the primary hormones that affect sexual development, and regulate other sexual organs and sexually differentiated behaviors.
''Secondary sex organs'' refer the rest of the reproductive system, whether internal or external. The Latin
term ''genitalia'', sometimes anglicized as ''genitals'', is used to describe the externally visible sex organs: in male mammals, the penis
; and in female mammals, the vulva
and its organs.
In general zoology, given the great variety in organs, physiologies, and behaviors involved in copulation
, male genitalia are more strictly defined as "all male structures that are inserted in the female or that hold her near her gonopore
during sperm transfer"; female genitalia are defined as "those parts of the female reproductive tract that make direct contact with male genitalia or male products (sperm, spermatophores
) during or immediately after copulation".
External and internal organs
The visible portion of the mammalian genitals for males consists of the scrotum
; for females, it consists of the vulva
, etc.) and vagina
In placental mammals
, females have two genital orifices, the vagina and urethra, while males have only one, the urethra
Male and female genitals have many nerve endings, resulting in pleasurable and highly sensitive touch. In most human societies, particularly in conservative
ones, exposure of the genitals is considered a public indecency
, sex organs include:
In typical prenatal development
, sex organs originate from a common primordium
during early gestation
into male or female sex
es. The SRY gene
, usually located on the Y chromosome
and encoding the testis determining factor
, determines the direction of this differentiation. The absence of it allows the gonads to continue to develop into ovaries.
Thereafter, the development of the internal, and external reproductive organs is determined by hormones produced by certain fetal gonads (ovaries or testes) and the cells' response to them. The initial appearance of the fetal
genitalia looks basically feminine: a pair of "urogenital folds
" with a small protuberance in the middle, and the urethra
behind the protuberance. If the fetus has testes, and if the testes produce testosterone, and if the cells of the genitals respond to the testosterone, the outer urogenital folds swell and fuse in the midline to produce the scrotum; the protuberance grows larger and straighter to form the penis; the inner urogenital swellings grow, wrap around the penis, and fuse in the midline to form the penile urethra.
Each sex organ in one sex has a homologous
counterpart in the other one. See a list of homologues of the human reproductive system
. In a larger perspective, the whole process of sexual differentiation
also includes development of secondary sexual characteristics
such as patterns of pubic and facial hair and female breasts that emerge at puberty. Furthermore, differences in brain structure arise, affecting, but not absolutely determining, behavior.
encompasses the development of genitalia somewhere between typical male and female genitalia. In humans societies, once a child is born, parents may be given the authority to decide whether or not to modify the child's genitalia, and if so what sex to assign the child
. Some scenaria have medical staff choose, either by the parents' or their own authority. If it is decided that the genitalia should be modified, and the result is incongruent with the child's future gender identity
, the child may begin to show symptoms of gender dysphoria
, which can lead them to a life of discomfort until they are able to remedy the issue.
Modifying the genitalia of intersex children is broadly considered to be a violation of the child's human rights
[Involuntary or coerced sterilisation of intersex people in Australia](_blank)
, Australian Senate Community Affairs Committee, October 2013.
Because of the strong sexual selection
affecting the structure and function of genitalia, they form an organ system that evolves rapidly. A great variety of genital form and function may therefore be found among animals.
In many other animals a single posterior orifice, called the cloaca
, serves as the only opening for the reproductive, digestive, and urinary tracts (if present). All amphibians, birds, reptiles,
some fish, and a few mammals (monotremes, tenrecs, golden moles, and marsupial moles) have this orifice, from which they excrete both urine and feces in addition to serving reproductive functions. Excretory systems with analogous purpose in certain invertebrates are also sometimes referred to as cloacae.
The organs concerned with insect
mating and the deposition of eggs are known collectively as the external genitalia, although they may be largely internal; their components are very diverse in form.
Slugs and snails
The reproductive system of gastropods (slugs and snails) varies greatly from one group to another.
are flat worms widely used in biological research. There are sexual and asexual planaria. Sexual planaria are hermaphrodites, possessing both testicles and ovaries. Each planarian transports its excretion to the other planarian, giving and receiving sperm.
The life cycle
of land plant
s involves alternation of generations
between a sporophyte
and a haploid gametophyte
. The gametophyte produces sperm or egg cells by mitosis
. The sporophyte produces spores by meiosis
which in turn develop into gametophytes. Any sex organs that are produced by the plant will develop on the gametophyte. The seed plant
s, which include conifer
s and flowering plant
s have small gametophytes that develop inside the pollen grains (male) and the ovule
Sexual reproduction in flowering plants
involves the union of the male and female germ cells, sperm and egg cells respectively. Pollen is produced in stamen
s, and is carried to the pistil
, which has the ovary
at its base where fertilization
can take place. Within each pollen grain is a male gametophyte which consists of only three cells. In most flowering plants the female gametophyte within the ovule consists of only seven cells. Thus there are no sex organs as such.
* Genital modification and mutilation
* Human sexuality
* Intimate part
* Obstetrics and gynaecology