Although there is a tendency to think of the embryo as a relatively sexless creature, his or her sex is determined at the moment of fertilization. The sperm contributes either an X or a Y chromosome to pair with the X chromosome of the female ovum. Barring any idiosyncracies during cell division, the outcome is either an XX (female) or XY (male) combination.

The XX or XY chromosomal combination in turn determines whether the undifferentiated fetal gonads become ovaries or testes at about 5 to 6 weeks of fetal life. After this point in sexual differentiation, the sex chromosomes appear to have no more direct influence.

Further sexual differentiation occurs under the influence of hormones. In order for the fetus to develop into a male, hormonal induction is essential. It is believed that a testicular inductor substance leads to the elaboration of fetal androgens that suppress the precursors of the oviducts (Mullierian ducts) and the ovaries (gonadal cortex). The rest of the male genital tract then differentiates into appropriate structures. Usually these changes occur between the seventh and the twelfth prenatal weeks of life. Unless androgens are present, the external genitalia of the fetus will appear female regardless of whether an XX or an XY chromosomal pattern exists. Although hormonal influence can still alter the genital appearance, biologic sex is fairly well established by the twelfth week of fetal life.

Although estrogens are probably not essential for the continued feminization of the reproductive tract, estrogens are released in the genetically female embryo. If the gonads are removed before the seventh week of prenatal life, the fetus will continue to develop as a female. There does not appear to be an ovarian inductor substance elaborated in the female, as is necessary for the male. However, estrogens are required for full development of the female genital pattern. It is believed that the autonomous nature of female development probably derived from the evolutionary problem of bearing live young without feminizing the male embryo with maternal estrogens.

Hormonal induction enables the male embryo to offset the influence of his mother's hormones with his own testosterone. However, this hormonal induction process may also introduce the potential for solidifying or confusing gender. It is believed that there is a critical stage, just before or soon after birth, at which another set of sexual controls is introduced. Testosterone may influence the hypothalamus, in a process referred to as sex-typing of the brain. The brain that is influenced by testosterone will develop the male, or acyclic, pattern for the release of pituitary hormones, the gonadotropins. In the female-typed brain, a cyclic pattern of gonadotropin release is established. After this second critical period, the individual becomes resistant or immune to the influences of either testosterone or estrogen, depending on his or her sexual differentiation.

There appear to be two critical points in the evolution of gender and gender identity: the prenatal point at which development of the internal and external genitalia is induced in the male embryo by testosterone, and the point, during prenatal life or early childhood (sometime before 3 years of age), when the brain becomes appropriately sex-typed. It may be that this sex-typing of the infant brain is indeed responsible for his behavior, which is reaffirmed according to his biologic sex throughout the remainder of his or her life, as well as for gender disorders that may be hormonally induced.

The child who is born with ambiguous genitalia becomes the object of parental confusion unless definitive counseling is obtained early. Money an Ehrhardt believe that 18 months is an age ceiling for reassignment of gender identity. By this age, behavior patterns of those who are significant in the child rearing are well established.

Infants receive biologic stimulation of their erogenous zones, most frequently from the mother during the oral stage of their existence. The infant is able to seek pleasure, warmth, and satisfaction primarily through his mouth. It believed that during this stage of development the sexual drive is manifest predominantly in sucking and the wish for warmth. Some theorists believe the erections seen in infant males are caused by some form of genital excitement. is not uncommon or abnormal for infants to explore their genitalia.

The child's genital sex as well as the parent's response to his or her sex both influence further sexual development. Although the biologic aspects of infantile sexuality are important, psychologic factors, such as evolving feelings of maleness or femaleness, and social factors, such as rearing, that reconfirm the child's sexual identity also play crucial roles.

About The Author
David Crawford is the CEO and owner of a Vigrx Plus Reviews company known as Male Enhancement Group which is dedicated to researching and comparing male enhancement products in order to determine which male enhancement product is safer and more effective than other products on the market. Copyright 2010 David Crawford of Natural Penis Enlargement This article may be freely distributed if this resource box stays attached.