15+Reproductive+Physiology

Reproductive Physiology Chapter 20 **__Content Summary __** //Chapter 20 covers the reproductive system in every aspect. I found this chapter to very interesting overall because I have had one child already and the developmental aspect of a fetus fascinates me. The entire process of the development of a baby is incredible, and the processes that go into this are amazingly intricate. This chapter covers a multitude of topics including sexual reproduction, endocrine regulation of reproduction, the male reproductive system, the female reproductive system, menstrual cycle, fertilization, pregnancy, and parturition. Although all of these topics are equally interesting, the three that I enjoyed the most were the sexual reproduction, endocrine regulation and reproduction, and the fertilization, pregnancy, and parturition sections. //

//The opening section of the chapter deals with the sexual reproduction of the human body. Although this may sound to some like the “Birds and the Bees” talk that we have all endured, it really takes on a whole new light, and focuses more on how we are formed and not how we are made. The sex of a zygote all depends on the specific sperm that fertilizes the egg. When a sperm with the XX chromosomes fertilizes the egg there will be a female produced. As for when the XY chromosome is the one to fertilize the egg, the egg keeps the Y chromosome from the sperm and pairs it with the X chromosome from the mother, and creates the XY zygote or the male. The zygote with the XY genotype develops testes, and these testes cause the production of mullerian inhibition factor. This MIF is responsible for the degeneration of the female sex organs; at the same time the production of testosterone by the testes promotes the growth and development of the male sex organs. The many abnormalities and disorders of embryonic development can be explained in terms of physiology of the developmental processes. //

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//The next subject that I found to be highly interesting was the endocrine regulation and reproduction. The endocrine system plays a large role in the reproductive system in several ways. The follicle-stimulating hormone, or FSH, and the luteinizing hormone, or FH, are what stimulates the gonads, and they are both considered to be anterior pituitary hormones. In this section of the reproductive system the brain has a large role on what is produced when and where. The hypothalamus secretes the gonadotropin-releasing hormone, or GnRH, which regulates the FH and FSH levels. But this is not the only control over the release of FH and FSH because they are also under the control of the gonads. This is possible by the means of negative feedback from the gonadal steroid hormones and by inhibin. The occurrence of puberty in humans is caused by the decreased sensitivity of the hypothalamus and the pituitary gland to detect negative feedback about the sex steroid hormone. Also the human sexual responses can be divided into 4 separate categories. They are in order as listed: excitation, orgasm, plateau, and resolution. Although males and females do not share the same accessory sex organs, their patterns are somewhat similar and follow the pattern that was just stated. //

//The next subject that I chose is actually three subjects crammed into one section in the book. These three subjects are fertilization, pregnancy, and parturition. Like I previously stated I think that this is so interesting to me because of the fact that I have already given birth to one child, so these facts resonate deeper in me. Before the sperm can enter the corona radiata and zona pellucida it must undergo an acrosomal reaction. After the fertilization occurs, the meiotic division of the second oocyte is completed, and the result is a second polar body that subsequently degenerates. The oocyte goes through a process to form a diploid zygote, and from there it undergoes cleavage in order to become a morula, and in time a blastocyst. Once it has reached the form of a blastocyst, it will become implanted in the endometrium between the fifth and seventh days after fertilization. The placenta plays a vital role in the health of the embryo prior to delivery. In order to do this the placenta secretes chorionic somatomammotropin, chorionic gonadotropin, and steroid hormones. Actions of the hCS act in a simalr fashion to that of growth hormone. The hCG work in the similar fashion to that of FSH and FH. The major steroid hormone secreted by the placenta is estriol. Contraction of the uterus is caused by oxytocin, and happens only around the time of labor. Another cause of these is prostaglandin that is produced within the uterus itself. // Source (Physiology Book)

**__Application __** //Obviously this is something that all of us should take a certain interest in, and should at least know the basics for our own sake. The entire process of reproduction relates to me personally because I have already given birth to one beautiful daughter. The information that I learned throughout this chapter explains a lot about the body throughout the process of a pregnancy. The knowledge of how the embryo takes on a sex is a very interesting topic to me because there are all sorts of theories on online about how you can force your body to have one or the other, but I have had my doubt in their processes. The hormones for a woman have to be very informational in this chapter because it kind of gives you an idea of what is happening throughout the changes that take place in your body during and through a pregnancy. Some women say that the hormonal rush is the worst part about giving birth and the process of a pregnancy and it is nice to know a little bit more about how or why they would say such a thing. //

**__Essential Questions __** //The menstrual cycle is split up into phases. During the follicular phase, FSH stimulates the ovarian follicles from the anterior pituitary. Follicles grow, mature, and secrete increasing amounts of estradiol because of the FSH stimulation. The rapid increase in the FSH levels causes a surge from the anterior pituitary containing LH as a result of positive feedback. The LH and FSH are a product of the GnRH which stimulates the anterior pituitary to secrete them. The increased LH around day 14 triggers ovulation. The luteal phase begins after the empty follicle has been stimulated by the LH and becomes corpus luteum. The LH and FSH then receive negative feedback from the rising levels of progesterone and estradiol in the early parts of the luteal phase. With the lack of stimulation from the LH, the corpus luteum retreats at the end of the luteal phase. This causes a decline in the secretion of the progesterone and estradiol. This is thus the beginning of a new cycle. The rise in the estradiol levels throughout the luteal phase causes the onset of the proliferative phase of the endometrium. Also the secretion of the excess progesterone during the luteal phase gives way to the secretory phase of the endometrium. // Source (Physiology Book)

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