Reproductive System and Developement By Bryce Tappan

Function of the Reproductive System The reproductive system has several vital functions, and they differ a bit from male to female. The shared functions are that both male and female reproductive systems make gametes and hormones. Also, the reproductive system provides a means for the male gamete (sperm) to travel to the female egg. Within the female, the reproductive system functions to help the zygote develop. http://www.livestrong.com/article/37137-reproductive-system-functions/

Sexual vs. Asexual Asexual reproduction means that an organism can proliferate without intercourse between cells of different genders. Normal cells grow in this fashion; they require no input from outside cells, and the offspring are essentially clones. Sexual reproduction occurs when one gamete, the male cell, fertilizes another gamete, the female cell, forming a zygote. http://www.biotopics.co.uk/genes1/asexual_and_sexual_reproduction.html

Examples of Asexual Reproduction Many plants produce asexually: Chlorophytum makes “plantlets” that are genetically identical to the parent plant and will grow up to be almost identical. Bacteria- most bacteria reproduce asexually from a process called binary fission. Liverworts, a bryophyte, produces asexually http://www.biotopics.co.uk/genes1/asexual_and_sexual_reproduction.html http://en.wikipedia.org/wiki/Marchantiophyta

Spermatogenesis Spermatogenesis is the process in which haploid sperm cells are created in the testes, and it can be divided into three stages. The first stage, spermatocytogenesis, begins in the seminiferous tubule within the testes. Initially, these cells divide through mitosis, but after a certain number of cells exist they divide meiotically, creating haploid cells called secondary spermatocytes. They then divide again to create spermatids which go dormant and mature into spermatozoa. http://www.rci.rutgers.edu/~uzwiak/HumanSexuality/HSSpringLect3.html

Oogenesis Oogenesis occurs within the follicles of the ovaries. Oogenesis is the creation of a female sex cell, an egg, that is also a haploid cell created from an original diploid cell called a oocyte. Each oocyte divides meiotically and leads to the production of a single egg and three polar bodies. The fact that the egg and the sperm are both haploid cells allow for fertilization to create a diploid zygote with genetic variation from its parents. http://www.sparknotes.com/testprep/books/sat2/biology/chapter7section2.rhtml

Unequal Division of cytoplasm in oogenesis When an oocyte goes through meiosis, a large haploid oocyte and a smaller polar body are created. The second division is once again unbalanced, creating a large ootid and an even smaller polar body. The unequal division is an advantage because it gives the one egg a large amount of cytoplasm and little to the nonfunctional polar bodies. http://www.madsci.org/posts/archives/2004-05/1084815953.Dv.r.html

Menstrual Cycle The menstrual cycle occurs to prepare females for the possibility of reproduction in three main stages: the follicular phase, ovulation, and the luteal phase. About once a month, the uterus grows a new endometrium (lining) to get ready for a fertilized egg. If no fertilization occurs, then the uterus disposes of the lining through menstrual bleeding. The menstrual cycle is regulated by hormones such as estrogen and progesterone. Build up of hormones prepare the uterus for pregnancy, and a drop in hormones triggers periods. http://women.webmd.com/tc/normal-menstrual-cycle-topic-overview

Estrous Cycle Both the estrous cycle and the menstrual cycle are regulated by hormones, however there exist differences between the two cycles as well. The estrous cycle is different from the menstrual cycle in that the endometrium is absorbed at rather than shed as it is in the menstrual cycle. Estrous Cycle vs Menstrual Cycle.doc - Strathmore High School

Hormonal Control  Luteinizing hormone and follicle-stimulating hormone, both produced in the pituitary gland, facilitate the ovaries to begin ovulation. The ovaries then produces estrogen and progesterone, which trigger the uterus to become ready for a possible fertilization. When levels of these hormones decrease, the lining of the uterus breaks down and begins to shed. http://www.merckmanuals.com/home/womens_health_issues/biology_of_the_female_reproductive_system/menstrual_cycle.html

Feedback Mechanism The release of many hormones are controlled by what is called a negative feedback mechanism. For example, in the menstrual cycle, the pituitary gland releases hormones to trigger certain events. When the body senses that there is enough, or an excess, of hormones to perform a duty, the gland that excretes those hormones is temporarily turned off. A negative feedback system is one that produces something that eventually triggers the shutdown of the producer. http://www.hormone.org/Endo101/page3.cfm

Cleavage In multicellular organisms, cleavage is the first step of development. The single celled zygote divides mitotically to produce a blastula. The proliferation of cells allows for a decrease in the size of each cell, but still increases the surface area to volume ratio, which gives the blastula access to more oxygen and resources. http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookreprod.html#Fertilization%20and%20Cleavage

Cleavage http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookreprod.html#Fertilization%20and%20Cleavage

Gastrulation Gastrulation is the process in which the blastula changes shape to form three layers of cells: the ectoderm, the mesoderm, and the endoderm. The ectoderm leads to the formation of the skin, hair, CNS, sweat glands, and epithelium. The mesoderm creates muscles, bones, cartilage, blood, the reproductive organs and kidneys. The endoderm forms respiratory and digestive organs, many glands, the endocrine system, liver, pancreas, and gall bladder. http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookreprod.html#Fertilization%20and%20Cleavage

Organogenesis Organogenesis is the process in which the ectoderm, endoderm and mesoderm develop into the body parts of a living creature. The germ layers, listed above, each form different parts of the body as follows in the next slide. www.wikipedia.org

Germ layers develop into: Ectoderm-forms the spine, peripheral nerves, brain, skin, and the lining of mouth, anus, nostrils, sweat glands, hair and nails Endoderm- forms the gastrointestinal, urinary, and respiratory tracts, the endocrine system, and the auditory system Mesoderm-forms muscles, connective tissues, blood cells, the lining of coelums, and the gonads. www.wikipedia.org

Morula, Blastula, Gastrula Once the zygote begins to divide, it forms a ball of out of cells called blastomeres, and this ball is called a morula. Within the morula, a hollow cavity forms. Next in the development of the embryo is the blastula, which is a hollow ball of cells formed from the morula. Once the blastula has formed, the next step of development is the formation of the gastrula. The blastula is arranged in a way so that the ball has three layers of cells, called germ layers. These germ layers are the beginnings of the development of the body of the organism, which include the ectoderm, mesoderm, and endoderm. http://en.wikipedia.org/wiki/Morula http://en.wikipedia.org/wiki/Gastrula http://en.wikipedia.org/wiki/Blastula

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