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pared and contrasted with these of Chapter 12, which provides similar information for the male. Chapter 14 will cover the hormonal relationships of pregnancy, lactation, and development, as well as the hormonal aspects of fertilization and sex determination.

B. Characteristics of a Female

As discussed in Chapter 14, the gonads of both males and females in the early embryonic stage are morphologically identical. It is only after the onset of sex differentiation (during the fifth and sixth weeks of fetal development) that the inevitable consequences of expression of the genetic information resident in the XX (female) or XY (male) chromosomes normally manifest themselves to convert the "indifferent" gonads into the fetal female ovaries or male testes.

The female ovary has the dual function of being responsible for both the production and release of the germ cell or ovum as well as the biosynthesis and secretion of the key steroid hormones, progesterone and estrogen. These steroid hormones play a dominant role in the differentiation, growth, and maintenance of the sexual reproductive tissues necessary for continuation of the species.

Sexually the female can be classified by six characteristics: (1) chromosomal composition and structure; (2) gonads that are functionally and structurally ovaries; (3) female sex hormone production (cyclically in the adult); (4) external and internal genitalia that are morphologically appropriate for a female; (5) rearing as a female; and (6) self-acceptance of a female role.

Thus, the female sexual identity is the summation of the four genetically determined organic characteristics as well as the two psychological characteristics of gender role and sex of rearing. Studies by B. McEwen indicate the key role of the sex steroid hormones (both estrogens and androgens) early in fetal and postnatal development for the sexual development of the brain.

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