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Module 1: Módulo 8: Introdução ao sistema reprodutivo

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Introdução ao Sistema de reprodução

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The Human Reproduction System is a collection of organs for the production of offspring. Thus, succeeding generations are provided for the continuation of the species. In humans there are two distinctly separate sexes, male and female.

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The presence of different anatomical forms of the two sexes is called sexual dimorphism.

Sexual Dimorphism:
DI = two
MORPH = body form
SEXUAL = by virtue of sex
The contribution of hereditary materials by two parents increases the chances for improved genetic recombinations.

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Sex Hormones

Sex hormones are body chemicals associated with sex and sexual development. They belong to a chemical group called steroids. Sex hormones are formed primarily in two types of organs: the gonads and the adrenal cortex.

The adrenal cortex is the outer layer of the adrenal gland, which rests upon each kidney. The sex hormones of the female are called estrogens and progesterone. The sex hormones of the male are called androgens.

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Major Organ Subgroups

In both males and females, the organs of the reproductive system can be grouped according to function. These subgroups are the primary sex organs (gonads) and the secondary sex organs

In both sexes, there are certain structures at the surface known as the external genitalia.

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Common Embryonic Organs

In male and female embryos, there is a common origin of the organs of their productive system. (The organs of the urinary system share this common origin).

The importance of this common origin is that, under certain conditions, females may develop with males characteristics, males may develop with female characteristics, and even true intersexes may occur.

(True intersexes possess both male and female gonadal tissue.)

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Sex Determination

At the moment the egg is fertilized by the sperm, the new genetic combination determines whether the individual will be male or female.

Later in development, however, sex hormones play an important role in the production of sexual organs and characteristics.

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Gametes – Definition
Within the genetic makeup of each individual, there is a pair of chromosomes known as the sex chromosomes. There are two kinds of such chromosomes--X and Y.

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Meiosis

Within the gonads, there is a special type of cell division known as meiosis. The usual set of chromosomes is reduced in this reduction division. Thus, the gametes (ova or spermatozoa) have only a single set of chromosomes.

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Fertilization

In the final analysis, the production of a new individual is based upon the union of the male gamete (spermatozoon) with the female gamete (ovum). This process is called fertilization. At this time, a double set of chromosomes is reconstituted.

If the zygote (fertilized egg) has two X chromosomes, the individual will be female (XX).

If the zygote has one X and one Y chromosome, the individual will be male.