Introduction:

There are millions and million of people on this planet, and they all came from a sperm and an egg. It is so amazing to think that every human being is created from cells so small they can't even be seen with the naked eye. In every male and female the reproduction organs are much more complex then just a penis and a vagina. The extremely small characteristics in each person's sex organs, and the actions it takes to create another human being is pretty detailed. Without being able to have the proper function of these sex organs, procreation could not happen. Each child, male or female, are decided by two cells, and X or a Y. Every human being needs many hormones to maintain the proper function of their sex organs.












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Concept #1: Male reproductive system

There are cells inside the testes that secrete testosterone called Leydig cells. Testosterone is a hormone that stimulates the formation of the accessory sex organs, is needed for spermatogenesis, and to promote the development of the secondary sex characteristics. In order for the Leydig cells to be stimulated there needs to be increased levels of the lutenizing hormone, LH. Spermatogenesis is the making of sperm inside the testes, which is stimulated by the follicle stimulating hormone, FSH. The scrotum is a sac of skin that holds the testes. Inside of each teste are seminiferous tubules which account for most of the weight from the teste. The Leydig cells are the most abundant cells that are a part of the interstial fluid inside the scrotum, which also has blood and lymphatic capillaries. Inhibin is a hormone that is produced by different cells called Sertoli cells, which inhibits the FSH. There are negative feeback effects caused by the inhibin and testosterone to help maintain a constant level of the gonadotropins. The levels of testosterone tends to decrease in men past their 20's. Germ cells, or gametes, are formed in the gonads, which are the sperm in a male. Spermatogonia is when the germ cells travel from the yolk sac to the testes during embryonic development. These spermatogonia, also called spermatogenic stem cells, are located in the outermost part of the seminiferous tubules. Spermatogonia have 46 chromosomes, diploid cells, that must give rise to the mature haploid gametes. Meiosis, which contains many divisions, is a reproductive cells division where the diploid cells can then become haploid cells. Interconnected spermatids must be separated into mature spermatozoa by a process called spermiogenesis, which requires the action of the Sertoli cells. On the sperm cell there are histone proteins which are associated with DNA in the chromatin. Because the histones modification affect gene expression, the cell needs to allow for the future embryo to have healthy genes. Histones are replaced with protamines which compact the chromatin which then causes the nucleus to change shape during spermiogenesis. When the chromatin and the nucleus is changed, the flagellum and the acrosome come into place. The acrosome has digestive enzymes in it to aid in the reproduction process. There are many accessory sex organs in the male. The epididymus, which are extremely long when they are stretched out, lay on top of the testes and receive the tubular products. When the sperm enter the vas deferens, a single tube, they are nonmotile because of the low pH. The sperm then pass through the epididymus and undergo a maturation change that make them more resistant to temperature and pH. A prostatic fluid helps to neutralize the acidic fliud, so the sperm can become motile. The epididymus is the place where sperm are stored, and matured between ejaculations. As the sperm are passing along through the vas deferens, they then enter the pelvic cavity. The seminal vesicles add secretion of fructose which are energy for the sperm, they pass through their ducts, when this happens the vas deferens becomes an ejaculatory duct. The ejaculatory duct is pretty small because it then enters the prostate and then soon enters the urethra. The prostate adds its secretions forming a fluid called semen. If the penis maintains its erection, through blood, ejaculation can occur which releases the semen and sperm cells into the vagina.

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Concept #2: Female reproductive system

When X chormosomes from a female are joined with X chromosomes from a male, a female is going to be created. Female accessory sex organs begin from mullerian ducts. There are many hormones that are involved in the female reproduction system. Two ovaries about the size of almonds are suspended by liagments in the pelvic girdle. The fallopian tubes, also known as the uterine tubes, partially cover each ovary. Ovum, or eggs, are released from each ovary into the fallopian tubes in a process called ovulation. Ciliated epithelium cells that line the fallopian tubes help to draw the egg into each tube. The fallopian tubes are continuous with the uterus, also known as the womb. The uterus is a pear shaped muscular organ held in place by ligaments in the pelvic cavity. There are three layers that make up the uterus. Perimetrium is the outer most layer that consists of connective tissue. The middle layer is made up of smooth muscle and is called the myometrium. Endometrium is the inner most layer whicl is made of stratified, squamos, nonkeratinzed epithelium cells. The narrow part of the uterus forms a cervix which is also the opening into the vagina. The vagina is also known as the birth canal. Accessory sex organs to the female include the vagina, uterus, and fallopian tubes. The vagina opens up immediately posterior to the urethra opening. Labia minora and labia majora help to cover the openings of the vagina and urethra. The clitoris is a small structure that is mainly composed of erectile tissue.


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Concept #3: Fertilization and pregnancy

Fertilization happens when the sperm cell and the egg cell fuse together. Once the sperm and egg are fused together, the original 46 chromosomes are now restored. A zygote is the name for the fertilized egg. After fertilization occurs, the secondary oocyte completes it's meiotic division. Once the meiotic divisions are completed, the cell then undergoes mitotic divisions and forms a blastocyst. The cells of the blastocyst secrete a certain hormone that is detected in pregnancy tests called human chorionic gonadotropin, hCG. HCG also helps to maintain that corpus luteum in the mother and to prevent menstration. Fertilization usually occurs in the fallopian tubes. If the secondary oocyte has been ovulated but not fertilized there will be no second division of meiosis. Sperm can survive for up to three days in the female reproductive tract. Cleavage is the process that takes place about 30-36 hours after fertilization where the zygote divides through mitosis. The cleavage process keeps dividing until there is a ball of cells called a morula, which will enter the uterus about three days after ovulation has occured. The very early embryo doesn't attach to the uterine wall for another two days, while the morula undergoes changes that will convert it into a blastocyst. The blastocyst is a hollow stucture which consists of two parts. The first part is the inner cell mass which will become the fetus, and the second part is the chorion which will become the placenta. Around the sixth day the blastocyst will attach itself to the uterine wall with the first part containing the inner cell mass against the endometrium. Implantation happens around the seventh day when the blastocyst completely buries itself into the wall of the endometrium. Most miscarriages happen when the blastocyst can not bury itself in the endometrium wall. The maternal tissue and the fetal tissue together form a functional unit called a placenta. When the baby is ready to come out of the mother, there are very powerful contraction of the uterus. These powerful contractions are needed to expel the baby from the mothers body, also called labor. Oxytocin and prostaglandins are the hormones which the uterus needs to complete these contractions. The placenta produces a hormone called, coricotropin releasing hormone, CRH, which is believed to be the most important determing factor when childbirth will happen. Parturition is also known as childbirth. There are so many hormones that are essential for fertilization, pregnacy, and birth to happen. It's simply amazing how this process works.






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Application:

This system is probably the most personal system out of all the systems of the body. I am a woman and therefore I have the lucky privilege of being able to menstruate every month, and to bear children. As a nurse and as a woman being educated on this system is pretty much common sense. If I was a nurse and working on the obstetrics floor of a hospital, understanding the reproductive system is essential. Also if I was seeing a male patient who admitted to taking anabolic steriods, I need to know the affects those steriods have on his body. Muscle growth, acne, hair growth, deeper voice, and many more complications can happen to his body. Every person usually goes through puberty and understanding the processes and what is happening to the body is key. As a female, being educated on conception, pregnancy, and more helps me to understand this process better. My little sister is just turing thirteen years old and being there for her as her big sister through her puberty makes me feel good.

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Essential question:

There are millions of oogonia in the ovaries of a female about 5-6 months prenatally. Most of the oogonia die not too much longer through aptosis, which is cell death. The remaining oogonia being meiosis towards the end of pregnancy and then they are called primary ooctyes. There are approximately 2 million oocytes in a female newborn, each which is contained within its own hollow ball of cells called the ovarian follicle. When the female reaches puberty the number of oocytes is reduced to 400,000 and approximately 400 will be ovulated. These primary oocytes have not yet been stimulated to complete the first meiotic division, and are kept within very small primary follicles. When the follicle stimulating hormone, FSH, is stimulated some of the oocytes and follicles get bigger. The follicular cells divide and them produce many numerous layers of granulosa cells that will surround the oocyte and fill the follicle. Only some of the primary follicles will grow more from stimulationg, and they will then develop a bunch of fluid-filled cavities called vesicles. Once this process is completed the follicles are now called secondary follicles. When the secondary follicles fuse its vesicles to make a single fluid-filled cavity called an antrum. As soon as this happens, the follicle is now known as a mature follicle. While the follicle is developing the primary oocyte is completes its first meiotic division. Even though through a meiotic division two cells are formed, only one cell gets all the cytoplasm and its called the secondary oocyte. The other cell that does not receive any cytoplasm is called a polar body, which will eventually disappear. The secondary oocyte then goes through its second meiotic division, but is stopped at metaphase two because fertilization has not occured. A barrier to prevent fertilization is called the zona pellucida. Stimulation of the FSH from the anterior pituitary makes the granulosa cells secrete increasing levels of estradiol, or estrogen, as the follicles grow. Usually 10-14 days after the first day of menstruation only one follicle continues its growth to become a mature graafian follicle, while others will become atretic, or without an opening due to their failed rupture. The one follicle that is protected against atresia and develops into a fully mature graafian follicle becomes so large that it starts to bulge out of the surface of the ovary. Once the bulge becomes so large that it pops, or ruptures, the oocyte will leave and enter into the uterine tube. This whole process is called ovulation. There are many changes in the ovary after ovulation. The empty follicle will undergo many changes due to the lutenizing hormone, and become a corpus luteum. Ovarian follicles secrete estradiol, but the corpus luteum secretes estrogen and progesterone. If the oocyte is fertilized it will complete its meiotic divisions, and if it's not fertilized the corpus luteum will become a nonfunctional corpus albicans. The anterior pituitary secretes both the follicle-stimulating hormone, FSH, and the lutenizing hormone, LH. Both hormones help to support the cyclic changes and functions of ovaries. The secretion of both of those hormones are controlled by the GnRH, or gonadotropin-releasing hormone. The FSH and LH are constantly changing their levels throughout the month to promote the different phases of the menstrual cycle. The periodic shedding of the stratum functionale of the endometrium is called a menstrual cycle. Hormones help to thicken the layer of the endometrium prior to menstration. Twenty-eight days is the average number of days in a menstrual cycle. The first day of menstration, or bleeding, is usually called day one of the cycle. There are three phases during the menstrual cycle. Follicular phase is the first phase, and is from the first day of menstruation til the day of ovulation. Luteal phase is after ovulation until the first day of menstruation. During the follicular stage of the ovaries, some of the follicles grow, develop vesicles, and then become secondary follicles. Ovulation is influenced by the FSH stimulation, and the graafian follicle grows into the large bulge. The surge of LH causes the graafian follicle to burst, and either be fertilized or not. After ovulation, LH causes the empty follicle to become the corpus luteum. Progesterone levels in the blood are low before ovulation and very high after ovulation. The luteal phase is approximately one week after the ovulation occurs. There are also three phases of the endometrium which is the innermost lining of the uterus. The first phase is the proliferation phase, while the ovary is in the follicular phase. Secretory phase is the second phase when the ovaries are in the luteal phase. The last phase is the menstrual phase when the ovarian hormone levels fall during the later part of the luteal phase. All of these phases, processes, and hormones must work properly in order for everything to function correctly!

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References from top to bottom:

http://www.youtube.com/watch?v=V6wUsMXSy4A

http://www.homebusinessandfamilylife.com/images/male_reproductive_system.gif

http://www.health-res.com/EX/08-01-08/female_reproductive_system.gif

http://www.health.com/health/static/hw/media/medical/hw/hwkb17_014_01.jpg

http://spermvolume.net/files/2010/12/20101212130524_04b_sperm_cell.jpg

http://www.femalereproductivesystem.org/index_clip_image001.jpg

http://www.youtube.com/watch?v=UgT5rUQ9EmQ

http://allnatural.iespalomeras.net/imagenes-web/dibujos/meiosis.gif

http://www.mhhe.com/biosci/esp/2002_general/Esp/folder_structure/re/m2/s2/assets/images/rem2s2_1.jpg

http://www.youtube.com/watch?v=UgT5rUQ9EmQ

http://image.shutterstock.com/display_pic_with_logo/180811/180811,1259691810,1/stock-vector-nurse-and-baby-41986822.jpg

http://image.wistatutor.com/content/reproduction-in-animals/menstrual-cycle-phases.jpeg

http://www.youtube.com/watch?v=nLmg4wSHdxQ