63 Steps of Fertilization CapacitatingAcidic environment of the female reproductive tract causes small pores to open in the acrosome (“enzyme-loaded” head) of the spermAcrosomal reactionEnzymes released from acrosome digest the outer membrane surrounding the egg cell
73 Steps of Fertilization A single sperm cell fuses with the plasma membrane of ovumHead passes into the cytoplasmElectrochemical reaction in eggMakes membrane impermeable to other sperm
8FertilizationFertilization must occur within a very short window of opportunity.Egg is only fertile for hoursSperm can survive up to 5 days in the bodySex (copulation) must occur no more than 5 days before or 1 day after ovulation
9Pregnancy If pregnancy is established, menstruation does not occur. Fertilized egg is called a zygote.Once cell division brings the total cell count to around 8, it is called a blastocyst.Takes 3-5 days for blastocyst to travel through oviduct to uterus.Blastocyst must implant into endometriumOccurs 2-4 days after reaching the uterus
10FertilizationIf pregnancy is established, menstruation does not occur.Fertilized egg is called a zygote.Once cell division brings the total cell count to around 8, it is called a blastocyst.Takes 3-5 days for blastocyst to travel through oviduct to uterus.Blastocyst must implant into endometriumOccurs 2-4 days after reaching the uterus
11FertilizationIf pregnancy is established, menstruation does not occur.Fertilized egg is called a zygote.Once cell division brings the total cell count to around 8, it is called a blastocyst.Takes 3-5 days for blastocyst to travel through oviduct to uterus.Blastocyst must implant into endometriumOccurs 2-4 days after reaching the uterus
12FertilizationIf pregnancy is established, menstruation does not occur.Fertilized egg is called a zygote.Once cell division brings the total cell count to around 8, it is called a blastocyst.Takes 3-5 days for blastocyst to travel through oviduct to uterus.Blastocyst must implant into endometriumOccurs 2-4 days after reaching the uterus
13PregnancyDuring implantation, the blastocyst produces a hormone called HCGHuman chorionic gonadotropinPrevents degeneration of corpus luteumStimulates corpus luteum to increase progesterone secretionMaintains uterine liningPrevents contractionsPregnancy test detects HCG in the urine of women.“Turns the stick blue”
14PregnancyTissue grows out from the embryo and mingles with endometrium to form placentaA disc-shaped organSize of dinner plateWeighs less than 1 kg.Contains maternal & fetal blood vesselsNO mixing of maternal and fetal blood!!Diffusion of gasses, nutrients, & wastesContinues production of HCG, estrogen, progesteroneMaintains endometriumCorpus luteum not needed – dissolves
15PregnancyProgesterone & estrogen have a negative feedback effect on the hypothalamusNo secretion of FSHNo secretion of LHNo new follicles matureEmbryo remains firmly attached to placenta by umbilical cord.
16Pregnancy Umbilical cord Contains: 2 fetal arteries Fetus to placenta One fetal veinPlacenta to fetus
19Childbirth Also called parturition 38 – 42 weeks from conception Average = 40 weeksThree stages of childbirthLabourDeliveryAfterbirth
20Childbirth Labour Involuntary Rhythmic contractions of the uterus Causes cervix to openDiameter = 10 cmDeliveryInvoluntary uterine contractionsConscious abdominal contractionsMother forces baby out through cervix and vagina
21Childbirth Afterbirth Immediately after delivery Blood vessels in placenta contractPlacenta separates from uterine wallExpelled by muscle contractions
22Childbirth Why?? Nobody totally knows. Baby plays some role in the timing.Progesterone decreasesAllows uterus to contractOxytocin from posterior pituitaryStimulates stronger uterine contractionsRelaxinproduced by placentaCauses ligaments of pelvis to loosenLarger passageway for baby
23LactationDuring pregnancy, high levels of estrogen and progesterone prepare the breasts for milk productionEach breast has about 20 milk glandsConnect to the nipple by ductsBreast enlarges during pregnancy in preparation for lactationExpulsion of the placenta causes the mother's pituitary to secrete prolactin,Initiates lactation
24Lactation Prolactin inhibits the release of LH menstrual cycle is suppressed in nursing mothersThe high estrogen and progesterone levels during pregnancy are thought to inhibit release of prolactin
25Lactation The first fluid formed by the mammary glands is colostrum, Thickcontains lactose and milk proteins,lacks fatafter a few days, milk is producedOxytocin is released from hypothalamus when infant sucklesCauses milk to be released from mammary glands
26Fetal Development A blastocyst embeds in the uterine wall Consists of cells of the future embryoSurrounded by a sphere of cellsEmbryonic membrane (extra-embryonic membrane)Support the developing embryo
27Fetal Development Amnion Innermost embryonic membrane Next to baby Fluid-filled sac that cushions the baby
28Fetal Development Chorion Outermost membrane Part of the placenta Secretes HCG
29Fetal Development Umbilical cord Connection between mother and baby Belly-button to placentaCarries baby’s blood to and from placenta
30Embryonic Development Placenta (review)A disc-shaped organSize of dinner plateContains maternal & fetal blood vesselsNO mixing of maternal and fetal blood!!Diffusion of gasses, nutrients, & wastesContinues production of HCG, estrogen, progesterone
32Embryonic Development A blastocyst undergoes gastrulationSeries of cell movements and shape changesProduces an embryo with 3 cellular layersEctodermOuter layer of cellsWill become skin and nervous systemMesodermMiddle layer of cellsSkeleton, muscles gonads, kidneys, circulatory systemEndodermInner layer of cellsLiver, pancreas, lungs, lining of digestive tract
34Human Gestation 1st Trimester From fertilization to end of 3rd month (0 – 13 weeks)Zygote begins cell division as it moves down oviductBecomes blastocyst and implants in uterus
35Human Gestation 1st Trimester Development of body organs Heart starts beating by week 4Week 7, testosterone begins to be secreted if a Y-chromosome is presentThis testosterone causes development of testes.
36Human Gestation 1st Trimester By week-8 all major structures of the adult are present (in basic form)Embryo is now called a fetusEmbryo is most sensitive during first trimesterDue to rapid developmentSensitive to radiation and drugs
49An Amazing Story -- Aug.19, 1999Samuel Armas' tiny hand grips Dr. Joseph P. Bruner's finger just as Bruner finishes returning him to his mother's womb.Bruner, director of fetal diagnosis and treatment at Vanderbilt University Medical Center (Nashville), was performing a cutting-edge procedure on the 21-week-old fetus.The procedure on Samuel took about an hour.
50An Amazing Story -- Aug.19, 1999Bruner and Samuel's parents hope the surgery will alleviate the effects of spina bifida, a disabling birth defect in one or two of every 1,000 babies born.Because fetuses undergoing this procedure are so young -- Samuel could not survive outside his mother's womb -- this kind of surgery is gaining attention nationwide from the medical community and the media.
51An Amazing Story -- Aug.19, 1999During the procedure, surgeons remove the uterus from the mother, drain the amniotic fluid, perform surgery on the tiny fetus, replace everything and put the entire package back inside the mother.Dr. Bruner said regarding the picture, "The baby did not reach out," Bruner says. "The baby was anesthetized. The baby was not aware of what was going on."
52An Amazing Story -- Aug.19, 1999Bruner says he saw the hand "sort of pop up in the incision" on the womb, and he "reached over and picked it up."Samuel, now nearly 5 months old [may 2, 2000], & is “developing normally and hitting his monthly milestones. He smiles often and is nearly sitting up on his own.”It will take years to know how much difference the surgery made, but Alex Armas [father] says he's happy the photo has been seen by millions.
73Birth Control Sterilization Most effective In males vas deferens is cut off and sealedOnly effects sperm content of semen so minimal side effectsIn females tubal ligation or cutting of the oviductsDisadvantages of sterilization - hard to reverse
74Birth Control “The pill" A combination of estrogen and progesterone given for 21 days of the 28 day cycleEffectively shuts down FSH and LH production so follicles do not develop.Many of the early problems have been sorted out but side effects possible
75Birth Control Barrier Methods Diaphragms, Cervical Caps, Vaginal Sponges, CondomsCondomfits over the penis and prevents semen from entering the female;Diaphragmwhich fits over the cervix and prevents semen from entering the uterusboth of these methods are more reliable when used in conjunction with a spermicidal foam or jelly
76Birth Control IUD Inter-Utarian Device placed in the uterus by a physician,prevent implantation of the blastocyst in the endometrium.Best for women who have had one pregnancy, middle to older and are at low risk for STI’s
77Birth Control "Natural family planning" Requires knowledge of the day of ovulationIf known, can avoid the 4 days either side of ovulation to account for unusually long -lived sperm or eggs.Women need exceptionally regular cycles to be effective"Basal" body temperature measurements (T rises at ovulation), vaginal pH measurements (more alkaline), mucus thickness can help determine time ovulation.
78Birth Control "Morning after pill“ Most are essentially a controlled overdose of normal birth control pillsRU-486 now distributed by Planned Parenthood.Blocks progesterone receptors causing uterine lining to slough off taking embryo with it.Many people have ethical problems with these pills since they remove fertilized eggs.i.e. after "conception" has occurred.“abortion pill”
79Reproductive Technologies Ultrasoundthe use of high-frequency sound waves to visualize the fetusAmniocentesisa long needle is used to remove a sample of amniotic fluid from the amniotic sac surrounding the fetus,fetal cells in the fluid are cultured for 2 to 4 weeks and then analyzed for chromosomal defects and other genetic disorders
81Reproductive Technologies Chorionic Villi Sampling (CVS)a small sample of tissue is removed from the chorion,the fetal part of the placenta.Can be performed earlier in the pregnancy than amniocentesisresults can be obtained within a few daysgreater risk of spontaneous abortion from CVS than from amniocentesisethical considerations: essentially all detectable fetal disorders remain untreatable in the uterus, and many cannot be corrected even after birth
82Reproductive Technologies In Vitro Fertilizationova can be surgically removed from a woman whose oviducts are blockedThese are fertilized in a petri dish in a laboratoryThe resulting embryos can than be inserted into the woman's uterus (or into a surrogate mother's uterus)Ethical considerations: post-menopausal woman can now have children; in surrogacy, who is the legal mother???
83STIsYou need to know which STIs are bacterial (and therefore curable through antibiotics) and viral (uncurable)
84VirusBacteriaHPV (human papilloma virus) – Can cause genital warts, some strains can lead to genital cancersChlamydiaHerpesGonorrheaHIV (Human immunodefficiency virus) – Can develop into AIDSSyphilisThis website has more information on STIs and sexual health