chapter 46 is about animal reproduction we're going to be looking at both asexual and sexual reproduction they both occur in your animal kingdom sexual reproduction is when an offspring is formed by fusion of a male gamete a sperm and a female gamete an egg or an ovum that together combine to make a zygote asexual reproduction is when offspring are formed without the fusion of eggs and sperm genes come from one individual but there are possibilities of recombination so it does not necessarily mean via a sexual reproduction in animals that you're going to have identical offspring as from the parents mechanisms of asexual reproduction invertebrates reproduce by fission basically taking the parent splitting it into two or more individuals that are roughly the same size budding can occur where new individuals arise from outgrowths of existing individuals fragmentation when the body of that particular organism is broken into pieces and some ax or perhaps all of those pieces are able to develop into adults when this takes place you'd have to have reagent generation take place as well where the body parts are reformed and then parthenogenesis is when a new individual is developed from an unfertilized egg why would a sexual reproduction be advantageous are sessile animals that are unable to seek out mates or live in areas where there are not a lot of other animals of their particular species and this enables them to be able to reproduce it does allow you to produce lots of offspring at a single time and it would be advantageous in environments that are favorable for that particular species that are very stable because it's going to help to perpetuate those successful genotypes sexual reproduction pros and cons sexual females are going to have half the daughters then asexual females have since asexual females are going to just make copies of themselves with perhaps some genes that are being adjusted while sexual females have the option of having a male don't have the option will either have a male or a female regardless of this all eukaryotic species reproduce or almost all eukaryotic species are reproducing sexually in large parts genetic recombination some potential advantages include variation so that will allow for increased reproductive success in environments that are varied being able to have an increase in adaptations to be more successful in changing environments and again the genes shuffling which hopefully can help to minimize deleterious genes hopefully eventually eliminate them from the population although that takes a lot of time so asexual reproduction you've got a female it makes copies of itself which then can make other copies of female so you see lots of females going through it whereas with sexual reproduction you will either have in generation 2 from that female a male or a female and it can keep going for their reproductive cycles animals in general are going to have reproductive cycles that kind of relate to seasons changing their cycles are controlled by your hormones and by environmental cues seasonal temperature can play a role in this so climate change unfortunately can have a negative impact on reproductive success ovulation is when mature eggs are released at the midpoint of the females reproductive cycle there are animals that can reproduce both sexually and asexually depending on what's going on in their environment sometimes finding a partner can be challenging hermaphroditism is when the individuals have both male and female reproductive systems this allows them to mate or to hermaphrodites to mate or for them to self fertilize some species undergo sex reversals certain oysters can switch from male to female some coral reef fish can switch from female to male and then we talked about partha Genesis earlier fertilization is going to be dependent on mechanisms that are able to bring sperm and eggs together from the same same species so external fertilization the eggs are shed by the female and are fertilized by sperm externally internal they're deposited near the in or near the female reproductive tract and fertilization takes place there regardless of how the eggs are fertilized timing plays a critical role environmental cues pheromones courtship behavior will all be involved in that determining if the fertilization is going to take place so there we have a couple of frogs ensuring survival of offspring internal fertilization will result in fewer gametes and being produced but also a higher survival rate of those fertilized eggs Azai goats internal fertilization is also seen to be associated with enhanced protection of the embryos and care of the young by the parents embryos of some terrestrial animals will have eggs that have calcium and protein containing shells internal membranes which kind of help provide support nourishment other animals will keep the embryo inside the female where it develops lots of animals parental care especially when those offspring are first born will help to ensure their survival so there we have a spider carrying the offspring and believe this is a male spider carrying his offspring on his back Gami prediction and delivery to reproduce sexually you've got to be able to make gametes most species are going to have gonads which are the organs that make those gametes some simple systems will not have actual gonads but they'll have undifferentiated tissue that can form gametes and others have more elaborate systems with tubes and glands that are able to carry and nourish and protect those camis as well as they're developed on the embryos that were they were developed from okay so there's a male fruit fly and a female fruit fly and you can see some of the reproductive organs that even these tiny flies can have reproduction partners monogamy is rare males and our females have evolved mechanisms to decrease the chance of their particular mate meeting with a nub mating with another individual and females can have some influence on the reproductive success of their mates so next section is going to focus on reproductive organs we're going to be focusing on the human reproductive system for females the external reproductive structures include the clitoris and two sets of labia surround that and the vaginal opening your internal reproductive structures are your ovaries or should be to present along with another long with a system of ducts and chambers aka the uterus that are able to if the gametes where they need to go and how's the embryo and subsequently the fetus okay more with the ovaries or female go meds they lie in the abdominal cavity and they're in a tough protective capsule kind of provide some extra protection there they contain lots of follicles that were born at birds and we're going to spend a lot more time with oh genesis in our next chapter these eggs are partially developed insights and they are surrounded by follicle support cells and they are arrested in their development at that point until a female is able to go through a menstrual cycle and during those menstrual cycles the new sites continue their growth they develop into an o them again through Genesis ovulation is when the egg cell is expelled from the follicle and the cells that are there are able to provide Esther prior to that ovulation process to help that follicle out and then the remaining follicular tissue that remained and your ovary will grow and form the corpus luteum which is able to secrete progesterone and that helps to maintain the lining and the uterus in the event of a fertilized egg and if that egg is not fertilized the corpus luteum is disintegrating the egg cell moves from the ovary touch about some ducts to the uterus via fallopian tube or an OVA duct there are silly of there and the oviduct that help get the egg to the uterus which is pretty thick and muscular and it's also known as the womb the lining of the uterus has lots of blood vessels again that's what the corpus luteum is trying to help support endometrium the uterus narrows at your cervix and then opens into the vagina the vagina itself is a thin walled chamber that's where sperm are deposited during copulation it's where the birth canal is present the vagina opens the outside of the vulva where you have your labia majora labia minora hymen and claryce and the clitoris has a head of called a glans just covered by the prepuce and the vagina the labia minora and the clitoris all have lots of blood vessels and the clitoris itself has lots of nerve endings the mammary glands are not specifically a part of the reproductive system but they are important because they have small sacs of epithelial tissues that are able to secrete milk which moves through ducts into the nipple so that it can provide the offspring with nourishment now reproductive anatomy external structures are your scrotum in your penis internal reproductive structures are the gonads there's to each there's at Estes or two testes that produce your sperm and hormones accessory glands and ducts the testes are your male gonads they are a set of highly coiled tubes that are surrounded by connective tissue they in the abdomen and then they descend into the scrotum shortly before a male is born smell for sorry sperm form and these seminarist tubules lytic cells are producing hormones testosterone various androgens and are scattered throughout the tubules sperm cannot be produced internally because of the body temperatures that are present in the mammal it's about two degrees less outside and so that is why the testes are located in this scrotum the temperatures a little bit lower there and it would be in the abdominal cavity ducts from the seminiferous tubules of at estes sperm move through the coil tubules of the epididymis that's where they mature during ejaculation and they are propelled through the muscular vas deferens and the ejaculatory duct and they exit through the urethra semen are not just sperm they also contain secretions from three sets of accessory glands the seminal vesicles that are located below and behind the bladder contribute over half of the volume that is making it the same in the prostate gland surrounds most of the upper portion of the urethra it's able to secrete its products directly into it through several ducts so that adds to it then you have the bubble urethral glands which are small glands located just below the prostate okay don't know why that's showing up and they secrete a clear mucus just before ejaculation that helps to neutralize any acidic urine that is still present in the urethra so the penis is the male copulatory organ the ejaculatory duct joins the urethra and the penis so that the semen can move through it we deposit in the female it has three cylinders of spongy erectile tissue when it is sexually aroused the tissue fills with blood from the arteries which is what causes the erection to take place the head of the penis is a glans and it has a thinner skin covering the prepuce and the shaft which is a little more sense stimulation and placental mammals not humans have a baculum bone present in this organ damages Genesis again it differs between males and females because depending in large part based on the gametes that they form and their function sperm are much smaller and motile they have to move from male to female eggs are stationary they're larger and they have to be able to carry out their function within the female spermatogenesis the development of mature sperm constantly is taking place since very prolific millions of them are produced each day it takes about seven weeks for a sperm to form to develop new Genesis the making sorry the development of a mature egg is a lot longer again I said that earlier on that the oocytes are present in their immature form before birth and they do not complete their development until years or decades later so they were there in the female embryo but they are stationary until there are hormonal changes taking place in that female ways that they differ with sperm all four products of meiosis aren't able to develop into viable sperm while only one of the four is able to become an egg in a female the other three are polar bodies because again you want to have a greater division of cytoplasm in the egg since that's going to serve as the location for the embryo to grow and develop strategizes occurs throughout adolescence and adulthood we know that that is not the case with a genesis and a sperm again are produced continuously there are not the interruptions that we see take place in New Genesis ok so again just showing you the divisions that take place in meiosis we're gonna spend a lot more time on spermatogenesis a new Genesis and the next chapter in terms of different components of your sperm and your egg but you've got those kind of there for you as a reference but we'll come back to those more in the next chapter tropic and six hormones are going to play a role in regulating mammalian reproduction we talked a little bit about this and the endocrine system chapter human reproduction is coordinated by hormones via the hypothalamus the anterior pituitary and the gonads gennady trope and releasing hormone G and RH is secreted from the hypothalamus and that is what directs the release of FSH and LH follicular sorry follicle stimulating hormone and luteinizing hormone from the anterior pituitary these regulate various processes and the gonads and are able to give to help produce your sex hormones besides functioning and gamete sorry besides functioning and gamete production as well as sexual behavior they also play a role in developing both primary and secondary sex characteristics hormonal control for female reproductive cycles the hormones that are secreted go through a cyclical pattern we talked about prior to ovulation and AM atrium thickens with blood vessels to prepare for potential embryo to be implanted and then if it is not implanted that endometrium has to be shared through menstruation hormones link these two cycles the uterus changes are what define your menstrual cycle also known as the uterine cycle while the ovary changes are what are used to define the ovarian cycle so you see the hormones how hypothalamus is going to release GnRH which will be it stimulated when you have lots of estrogen and will be inhibited when you have a combination of both estrogen and progesterone the FSH and LH are going to be inhibited if you do have lower levels of estrogen so as you go through your cycle you will see that the pituitary gonadal opens FSH and LH are going to peak at ovulation and then they're going to go back down we have the follicle growing maturing ovulation is taking place the corpus luteum is growing and again if fertilization does not occur and an embryo does not become implanted in the uterus the corpus luteum begins to disintegrate as the follicle grows estrogen is secreted causing those estrogen to mass estradiol to increase and then we will see that peak and LH at the point of ovulation along with estrogen after ovulation has occurred in that corpus luteum is starting to grow we see that progesterone is starting to peak that's during the luteal phase we see the estrogen amounts are still higher but are starting to diminish but we have both of those present they're both being secreted by the corpus luteum and then again if there is no fertilization both of those hormones start to diminish so we don't see gnrh being secreted in large amounts during that Lydia phase because we have both estrogen and progesterone present we see that GnRH would be stimulated when the estrogen amounts are very high so that would be prior to ovulation and then and that's when we see that peak take place and then when we have the lower amounts of estrogen so at the very beginning and at the very end of this 28-day period we would have the anterior pituitary be negative received negative feedback in terms of releasing FSH and LH so GnRH gets released then FSH and LH and that those help to stimulate your follicles growing that would be in the follicular phase and during this phase you will see that those follicles as they're growing Mesa Kaleem ake a bulge that forms on the ovary once ovulation occurs and that secondary oocyte has been released the follicular tissue is going to turn into your corpus luteum and release both the estrogen and the progesterone the luteal phase and then once the there has been no fertile as a fertilizer no embryo has been implanted in the uterus the corpus luteum there disintegrates and the hormones start to diminish hormones are what are able to coordinate the uterine cycle with the ovarian cycle the thickening of the endometrium is going to occur with the puller if it of poor proliferative phase which is coordinating with your follicular phase nutrient secretion is going to take place during the secretory phase which course coordinates with the luteal phase again you want to make sure you have everything that you need for that embryo to be able to be successfully implanted and grow the endometrium is shedded during the menstrual flow flow phase which is going to coordinate with additional or Bavarian follicles growing and the cycle repeats itself if no embryo is implanted and the endometrium of the uterus uterine lining cells so the cells that are found in the ATAR sometimes will migrate to ectopic at locations locations outside of the uterus and these what cells will swell response to hormone stimulation they could end up on your ovaries they could end up on your intestines your your other organs other tissues other muscles and that would cause what when these cells swell in response to hormone stimulation endometriosis and because there is nowhere for those the cells to be shut off it just keeps going menopause after about five hundred cycles females will go through menopause which is when ovulating and menstruation are ceased this is not typical among animals and it's thought that it potentially has evolved to give the mother an opportunity to better care for children and grandchildren again that's just a hypothesis so menstrual versus estrus cycles we've been talking about humans and humans are the ones that are going to be having your menstrual cycles along with some other primary it's where that endometrium is shed through bleeding called menstruation and sexual receptivity is not limited to a particular time frame during that cycle extra cycles are what we see with most mammals the ovulation takes place after the endometrium thickens the endometrium is reabsorbed by the uterus and sexual receptivity is limited to a heat period where there will be some pronounced behavioural changes and then the length and frequency of estrus sorry about the misspelling there cycle will vary depending on your species so we've spent a lot of time talk about hormonal control the female system or I look at it now in terms of the male system FSH is going to promote search wholly cell activity which are what are able to develop nor nourish developing sperm LH regulates lytic cells which are secreting testosterone and other antigens that are made by the interstitial tissue which then can be used to promote sarandon Genesis we saw how estrogen and progesterone are able to work in a feedback way same or have a feedback mechanism same thing works with testosterone is able to regulate the production of GnRH and FSH and LH and sertoli cells also secrete it's a hormone inhibin which will reduce FSH secretion from the anterior pituitary okay so that's kind of showing you the mechanism that's taking place there what FSH and LH are affecting what they make what they are able to influence and then how some of the products of those the reactions that take place and the sertoli cells and the lytic cells are able to influence negatively continued release of those androgens and hormones and testosterone he was sexual response to reactions predominate in both sexes vasocongestion which is a filling of tissue with blood myotonia increased muscle tension sexual response cycle has four stages excitement plateau orgasm and resolution excitement is preparing for coitus sexual intercourse direct stimulation of genitalia helps to maintain that plateau phase and gets the vagina prepared to accept sperm orgasm is when you have the rhythmic involuntary contractions of the reproductive structures it's a shortest phase males semen is forced to their urethra emission and then it's ejaculated from their expulsion females the uterus now trying to contract but the inner two-thirds do not and during resolution organs are able to return to the normal state the muscles relax orgasm is not needed for females to be able to reproduce to be able to have a fertilized egg that gets implanted in the uterus the central mammals embryos develop fully within that mother's uterus you can kind of see the different steps there it talks about how an egg is able to develop into an embryo through a series of events we've gone through 1 2 3 so far or sorry we've gone to 1 and 2 we're going to look at 3 4 & 5 right now so conception fertilization of an egg is going to take place in the OVA duck the zygote begins to divide by mitosis which is going to take place through a process called cleavage cells continue to divide they will eventually give rise to a blastocyst we do a little bit with diversity of all assists with a central cavity this occurs about one week after conception when the blastocyst has formed it will become implanted in the endometrium and once it has implanted human chorionic gonadotropin will be released from it which is going to prevent menstruation from occurring and help to keep that blastocysts intact and once it is implanted is now a trophoblast pregnancy or gestation is carrying one or more embryos in the uterus the duration will play of pregnancy and species will depend on the body size and the Young's maturity when they are born some pregnancies will terminate spontaneously miscarriages due to chromosomal or developmental abnormalities ectopic pregnancy would occur if a fertilized egg starts to develop does not wait until it gets to the uterus it starts to develop in the fallopian tube the first trimester when we're talking about human gestation we typically have three trimesters approximately three months each first trimester is when you have the most significant changes further both the mom and the embryo the endometrium grows over the blastocyst during implantation the first two to four weeks the embryo is getting its nutrients directly from that endometrium layer the outer layer of the blastocyst the trophoblast mingles with the endometrium and will then form the placenta once that placenta is formed blood from the embryo will travel to the placenta through the arteries of the umbilical cord and in return via the umbilical vein so you've got your placenta that has formed again on the outside of the uterus the baby is growing and you can see there the arteries and the veins from the mother and how they are interacting with that placenta and the umbilical cord to the fetus if the embryos Liszt's during the first month of development you can have genetically identical twins if two eggs are released and fertilized you can have fraternal and genetically distinct distinct twins first trimester is when body organs are developed organogenesis major structures are all present by about eight weeks and that's when the embryo is called a fetus changes that must occur in the mother there's a mucous plug that forms to prevent against infection the placenta and the uterus continue to grow ovulation sees as well as the menstrual cycle breasts become enlarged and nausea is going to be common due to the hormones that are developing to help to maintain the fetus so there's five weeks 14 weeks and 20 weeks second semester fetuses continue to grow is quite active the mother may feel the fetus the uterus continues to grow the pregnancy starts to become more obvious hormone levels begin to stabilize and that human chorionic gonadotropin that prevents menstruation from taking place it's amounts will start to decline during the third trimester again fetus continues to grow fills up space within the embryonic membranes it's during this trimester the abdominal organs of the mother will start to become compressed and displaced there's local regulators and hormones and that work together estrogen oxytocin prostaglandins that help to induce and regulate labor and that's how childbirth is going to take place parturition labor has three stages typically the cervix needs to thin and open aka dilation the baby needs to be expelled or delivered and then the placenta has to be delivered as well so this is a great example of a positive feedback mechanism the estrogen that is released from the ovaries or secreted from the ovaries is going to activate oxytocin receptors on your uterus and so oxytocin which we're going to be getting from both the fetus and from the mothers posterior pituitary are going to cause the uterus to contract and that's going to make more oxytocin it's also going to cause the placenta to be stimulated to make prostaglandins which also are going to help to stimulate contractions and as both oxytocin and the prostaglandin amounts increase you will continue to have more contractions and the baby will be expelled from the uterus so dilation expulsion and then placental delivery why the mother immunes mother's immune system is able to tolerate having both the embryo and the fetus present we aren't quite a hundred percent sure why that is it's thought perhaps that there are some suppression issues of the immune response to this foreign body being present in the uterus contraception can prevent protect pregnancy deliberately there are three main categories of contraceptive methods preventing release of eggs and sperm keeping the sperm and eggs apart from one another and preventing embryo implantation you should talk to a healthcare provider for more information on the potential contraceptive methods and the choices in risk associated with them so here is kind of a summary of what the methods are for both males and females and what events they are interfering with ones we're going to talk about rhythm method natural family planning is when you refrain from intercourse when conception most likely Tim have a 10 to 20 percent pregnancy rate regardless quite as interruptus penis withdrawal before ejaculation is unreliable physical barrier methods condoms diaphragm cervical cap sponges will block fertilization and they result in a pregnancy rate less than 10 percent enter uterine devices IEDs that are inserted into the uterus so that they interfere with the fertilization implantation result in a pregnancy rate under 1% and female birth control pills that are hormonal contraceptives also result in pregnancy rates less than of 1% contraception abortion sterilization is permanent prevents the release of gametes tubal ligation ties off the open acts and the male reproductive system vasectomy I'm sorry tubal ligation ties off the over ducks and the female reproductive system vasectomy ties off the vas deferens and the male reproductive system abortion is terminating a pregnancy we talked about how miscarriages are basically spontaneous abortions due to some abnormalities in the fetus they occur in two up to one-third of all pregnancies ru-486 is a drug that can result in abortion within the first seven weeks of a pregnancy there are sometimes reproductive issues that need to be examined and ways that we can do that are your amniocentesis and chorionic villus sampling where amniotic fluid or fetal cells are taken and analyzed to determine if there are genetic issues that need to be addressed or to make sure that the parents are informed of and there are also non invasive procedures sonograms that help to kind of give doctors and parents some information about their fetuses condition genetic testing can cause or can pose some pretty serious significant ethical questions and cause parents to have to make some difficult choices we talked a little bit about that when we cover genetics infertility there's a lot of technology out there now that can help infertile couples in vitro fertilization it mixes eggs with sperm in culture dishes and then returns the embryo to the uterus at the eight-cell stage so after the cell has started to go through cleavage and then another one would be sperm being injected directly into an egg which is a type of IBS so in vitro is totally in a lab sperm injected directly into an egg with ivf our intracytoplasmic sperm injection ICSI