A. General Comments

The ultimate purpose of reproduction is to produce a new female or male in order to maintain or prolong the species. As described in Chapters 12 and 13 for the male and female, respectively, there is extensive anatomical and endocrinological specialization that, besides defining the individual's fundamental male or female status, collectively emphasizes his or her functional complementarity. It is the successful union both in an anatomical as well as in an endocrinological sense that is essential for procreation (i.e., the meeting of a competent sperm with the ovum). Thus, the fundamental unit of reproductive biology is not the individual, but the triad of the mother, father, and offspring. This chapter describes the human endocrinology that is unique to the processes of pregnancy and lactation. It is beyond the scope of this chapter to describe the cell biology and endocrinology involving the many growth factors and paracrine substances of growth and development of the fetus and placenta.

B. Sequence of Events in Reproduction

The process of conception or fertilization of an ovum by a spermatozoon initiates a complex series of developmental and metabolic events for both the fetus and the mother, which are controlled by an array of endocrine factors. In this regard, a primordial endocrine event occurring shortly after the merging of the spermatozoon with the ovum to yield the zygote is the determination of the sex or gender of the offspring. This next leads to the implantation process, which is followed by development of the placenta as a mechanism for delivering nutrients to the developing fetus. Eventually, through further endocrine intervention, parturition or birth occurs, which then initiates the process of lactation.


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