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The Reproductive System

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Physiology 1021
Sarah Mc Lean

MODULE 14 The Reproductive SystemThe sections that we have covered so far have all dealt with physiological systems whose primary function is to maintain homeostasis The combined functions of both male and female reproductive systems on the other hand are to pass on the genes of the individuals and to maintain the species Fetal Development of the Reproductive SystemEach cell in the body contains 23 pairs of chromosomes this includes a pair of sex chromosomes The sex chromosomes consist of a large X chromosome and a smaller Y chromosome All eggs contain an X chromosome while the sperm can carry either an X or Y chromosome The sex of the future baby is determined at the point of fertilizationif a sperm carrying the X chromosomes penetrates the egg carrying the X chromosome then a female will develop XX If on the other hand a sperm carrying the Y chromosomes fertilizes the X chromosome bearing egg then a male will develop XY However development of each respective reproductive tract does not begin immediately after fertilizationDuring the first 6 weeks of development male and female embryos contain common sometimes called indifferent gonads These structures will eventually form the testes in the male or the ovaries in the female There are also two sets of primitive reproductive tractsthe mesonephric or Wolffian Duct and the paramesonephric or Mullerian Duct With the correct cues these structures will form either the male or female reproductive tracts In the developing male embryo at roughly 6 to 7 weeks the presence of the Y chromosome causes the indifferent gonads to develop into the testes However in the developing female embryo at about 9 weeks of development the XX chromosomes are activated and ovaries developOnce the testes or ovaries have developed the reproductive tracts and external genitalia follow As mentioned on the previous page the reproductive tracts develop from two primitive ducts the Wolffian duct or the Mullerian duct Lets look at this nowIn the developing male fetus at 7 weeks testicular cells begin to produce Mullerian inhibiting hormone MIH which causes the Mullerian duct to regress Then at 9 weeks testicular cells begin to produce testosterone This small surge in testosterone stimulates the Wolffian duct to develop into the epididymis vas deferens seminal vesicles and the urethra The presence of testosterone also causes the development of the male external genitaliaIn contrast to the male the development of the female reproductive tract and external genitalia requires no hormonal control In the developing female since there is no Mullerian inhibiting hormone the Mullerian duct develops into the fallopian tubes uterus cervix and part of the vaginastructures we will see in more detail Also since no testosterone is produced in the female fetus the Wolffian duct regresses and female external genitalia developThe function of the male reproductive system is to produce the sex steroid testosterone to produce sperm called spermatogenesis and to deliver it to the female vagina As we will see testosterone has many effects throughout the body especially at puberty The female reproductive system is more complex and is responsible for producing the sex steroid estrogen and the hormone progesterone The female reproductive system also
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