WordNet

work as an intern; "The young doctor is interning at the Medical Center this year"
an advanced student or graduate in medicine gaining supervised practical experience (`houseman is a British term) (同)interne, houseman, medical intern
deprive of freedom; "During WW II, Japanese were interned in camps in the West"
happening or arising or located within some limits or especially surface; "internal organs"; "internal mechanism of a toy"; "internal party maneuvering"
occurring within an institution or community; "intragroup squabbling within the corporation" (同)intragroup
of or relating to the external sex organs; "genital herpes"; "venereal disease" (同)venereal
external sex organ (同)genital_organ, genitals, private_parts, privates, crotch

PrepTutorEJDIC

(特に戦時中)〈人・船など〉‘を'強制収容する,抑留する
『内側の』,内部にある / 『国内の』(domestic) / 内からとる,内用の
生殖の,生殖器の
=genitals

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/02/01 12:28:29」(JST)

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The sex organs of a green alga, Chara are the male antheridia (red) and female archegonia (brown).

A sex organ or primary sexual characteristic, as narrowly defined, is any anatomical part of the body involved in sexual reproduction and constituting the reproductive system in a complex organism, especially the external sex organs; the external sex organs are also commonly referred to as the genitalia or genitals.^[1]^[2]

Mosses, ferns, and some similar plants have gametangia for reproductive organs, which are part of the gametophyte.^[3] The flowers of flowering plants produce pollen and egg cells, but the sex organs themselves are inside the gametophytes within the pollen and the ovule.^[4] 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.

Terminology

The Latin term genitalia, sometimes anglicized as genitals, is used to describe the externally visible sex organs, known as primary genitalia or external genitalia: in male mammals, the penis and scrotum; and in female mammals, the clitoris and vulva.

The other, hidden sex organs are referred to as the secondary genitalia or internal genitalia. The most important of these are the gonads, a pair of sex organs, specifically the testes in the male or the ovaries in the female. Gonads are the true sex organs, generating reproductive gametes containing inheritable DNA. They also produce most of the primary hormones that affect sexual development, and regulate other sexual organs and sexually differentiated behaviors.

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".^[5]

Mammals

External and internal organs

The visible portion of the mammalian genitals for males consists of the scrotum and penis; for females, it consists of the labia, clitoris, and vagina.

In placental mammals, females have two genital orifices, the vagina and urethra, while males have only one, the urethra.^[6] Male and female genitals have many nerve endings, resulting in pleasurable and highly sensitive touch.^[7]^[8] In most human societies, particularly in conservative ones, genitals are considered a public indecency and sometimes even illegal if left uncovered in public.^[9]

In mammals, sex organs include:

Female	Male
Bartholin's glands Cervix Clitoris Clitoral frenulum Clitoral glans (glans clitoridis) Clitoral hood Fallopian tubes Labia Labia majora Labia minora Frenulum of labia minora Ovaries Skene's gland Uterus Vagina Vulva An image of human female external sex organs (shaved pubic hair)	Bulbourethral glands Epididymis Penis Foreskin Frenulum of penis Glans penis Prostate Scrotum Seminal vesicles Testicles An image of human male external sex organs

Development

In typical prenatal development, sexual organs originate from a common anlage anatomy during early gestation and differentiate into male or female variations. 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 reproductive organs and the external genitalia 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 (a few weeks after conception) 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 sexual 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.

Intersex is the development of genitalia somewhere between typical male and female genitalia. Once the child is born, the parents are faced with decisions that are often difficult to make, such as whether or not to modify the genitalia, assign the child as male or female, or leave the genitalia as is. Some parents allow their doctors to choose. If they do decide to modify the genitalia, they have approximately a 50% chance of getting genitalia that will match the child's gender identity. If they pick the wrong one, their child may begin to show symptoms of transsexualism, which can lead them to a life of discomfort until they are able to remedy the issue.^[10]

Because of the strong sexual selection affecting the structure and function of genitalia, they form an organ system that evolves faster that any other.^[11] A great variety of genital form and function may therefore be found among animals.

Plants

The life cycle of land plants involves alternation of generations between a sporophyte and a haploid gametophyte. The gametophyte produces sperm and/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 plants, which include conifers and flowering plants have small gametophytes that develop inside the pollen grains (male) and the ovule (female).

Flowering plants

Sexual reproduction in flowering plants involves the union of the male and female germ cells, sperm and egg cells respectively. Pollen is produced in stamens, 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.

References

^ "Sex organ (sɛks ˈɔːɡən)". Collins English Dictionary. Retrieved September 14, 2013.
^ P. R. Ashalatha, G. Deepa (2012). Textbook of Anatomy and Physiology for Nurses. JP Medical Ltd. pp. 252–274. ISBN 9350254239. Retrieved September 14, 2013.
^ "Mosses and Ferns". Biology.clc.uc.edu. 2001-03-16. Retrieved 2012-08-01.
^ "Flowering Plant Reproduction". Emc.maricopa.edu. 2010-05-18. Retrieved 2012-08-01.
^ Eberhard, W.G., 1985. Sexual Selection and Animal Genitalia. Harvard University Press
^ Marvalee H. Wake (15 September 1992). Hyman's Comparative Vertebrate Anatomy. University of Chicago Press. p. 583. ISBN 978-0-226-87013-7. Retrieved 6 May 2013.
^ Sexual Intimacy in Marriage William Cutrer
^ Daphne's Dance: True Tales in the Evolution of Woman's Sexual Awareness Brigitta Olsen
^ Unpopular Privacy: What Must We Hide? retrieved 9 February 2012
^ Fausto Sterling, Anne (2000). Sexing The Body. New York: New York. pp. 44–77.
^ Schilthuizen, M. 2014. Nature's Nether Regions: What the Sex Lives of Bugs, Birds, and Beasts Tell Us About Evolution, Biodiversity, and Ourselves. Penguin USA

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English Journal

Genetic of gonadal determination.

Morel Y1, Roucher F2, Mallet D2, Plotton I2.
Annales d'endocrinologie.Ann Endocrinol (Paris).2014 Apr 29. pii: S0003-4266(14)00039-0. doi: 10.1016/j.ando.2014.04.005. [Epub ahead of print]
Fetal sexual differentiation results from complex subsequent intracellular signaling and hormonal events that interact together in a definite timing. This process contributes to the setting of gonad determination, internal and external genitalia resulting in a female or male phenotype. Here, we revi
PMID 24793987

Characterization of a novel CYP19A1 (aromatase) R192H mutation causing virilization of a 46,XX newborn, undervirilization of the 46,XY brother, but no virilization of the mother during pregnancies.

Bouchoucha N1, Samara-Boustani D2, Pandey AV1, Bony-Trifunovic H3, Hofer G1, Aigrain Y4, Polak M2, Flück CE5.
Molecular and cellular endocrinology.Mol Cell Endocrinol.2014 Apr 4;390(1-2):8-17. doi: 10.1016/j.mce.2014.03.008. [Epub ahead of print]
BACKGROUND: P450 aromatase (CYP19A1) is essential for the biosynthesis of estrogens from androgen precursors. Mutations in the coding region of CYP19A1 lead to autosomal recessive aromatase deficiency. To date over 20 subjects have been reported with aromatase deficiency which may manifest during fe
PMID 24705274

Testicular migration chronology: do the right and the left testes migrate at the same time? Analysis of 164 human fetuses.

Favorito LA1, Sampaio FJ.
BJU international.BJU Int.2014 Apr;113(4):650-3. doi: 10.1111/bju.12574.
OBJECTIVE: To determine if the right and the left testes migrate at the same time during the human fetal period.SUBJECTS AND METHODS: We studied 164 human fetuses (328 testes) ranging in age from 12 to 35 weeks post-conception. The fetuses were carefully dissected with the aid of a stereoscopic lens
PMID 24238431

Japanese Journal

Activity of male internal genitalia and breeding season in the lesser Japanese mole, Mogera imaizumii, inferred from morphometric and histological analyses