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Sex chatting in face to face

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).

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.

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.

A sex organ (also called a reproductive organ, primary sex organ or primary sexual characteristic) is any anatomical part of the body in a complex organism that is involved in sexual reproduction and together constitute the reproductive system.

Planaria are flat worms widely used in biological research. Sexual planaria are hermaphrodites, possessing both testicles and ovaries.Each planarian transports its excretion to the other planarian, giving and receiving sperm.

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In typical prenatal development, sexual organs originate from a common anlage anatomy during early gestation and differentiate into male or female variations.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.A great variety of genital form and function may therefore be found among animals.