1. 6. Human Physiology6.6 Reproduction

2. Female reproductive systemOvaries : egg cells areproduced. Within the ovaries,each developing egg cell iscontained inside a follicle.Oviduct (also called a fallopianor uterine tube): narrow tubeabout 10 cm long, which servesas a passageway to the uterus.It is normally the site offertilization.Uterus: a hollow, muscular organwith thick walls. If an egg isfertilized by a sperm cell, theuterus functions to contain andprotect the developing baby.Cervix: connects the uterus tothe vagina.Vagina: has several functions: itreceives the penis and sperm 3. Male reproductive systemTestes: Sperm cells begin theirdevelopmentScrotum: a sac-like structure thatcontains the testes. One function of thescrotum is to house the testes outsidethe main body cavity, a location that is1 to 3C cooler than normal bodytemperature.Epididymis: Sperm complete theirdevelopment and are stored in a long,thin, coiled tube attached to each testis.Seminal vesicles, prostate gland, andbulbourethral glands: secrete fluids thatfunction in the transport and survival ofsperm: semen.Vas deferens: connecting ducts.Muscular contractions propel spermfrom the epididymis through the urethra.Penis: an organ consisting mainly of 4. Development of gametes 5. Development of egg cells By the time a human femalereaches puberty her ovaries containabout 400,000 follicles. Each folliclecontains a resting primary oocyte. Ovulation: approximately every 28days, hormones cause one follicleand the oocyte within it to mature,commonly called ovule. When thefollicle breaks open, the secondaryoocyte is released. Meiosis II is not completed unlessthe egg is penetrated by a spermcell. As soon as this occurs, thesecondary oocyte undergoes itsfinal meiotic division. This forms theovum, the mature egg cell with ahaploid nucleus that is capable offusing with the sperm nucleus. 6. Development of sperm cells The development of sperm cellsbegins when males reachpuberty. The process begins with theprimary spermatocyte within thetestis that undergoes meiosis andproduces four haploid spermcells. Sperm cells move from the testesto the epididymis where theycomplete their development. Amature sperm has a tail(flagellum) that enables it to swimwithin the female reproductive 7. Hormonal control in females Sexual maturity in women ismarked by the beginning of themenstrual cycles. These cyclescoordinate the development andrelease of an egg with theconditions required in the uterusto support a pregnancy.Anterior pituitary hormones The cycle is controlled by hormones from the brain (FSH and LH) and the ovary (estrogen and progesterone). FSH and LH are two hormonesOvarian hormonesthat are active at significantphases of human developmentincluding primary and secondarysexual characteristics. They areboth significant hormones in the 8. http://kidshealth.org/misc/movie/bodybasics/bodybasics_female_repro.htmlhttp://www.sumanasinc.com/webcontent/animations/content/ovarianuterine. 9. (d)(a) (e)(b) (g) (g) (c) (f) (d) (g)(a) FSH is secreted by the pituitary gland of the brain and stimulates the developmentof a primary follicle.(b) Primary follicle cells secrete estrogen which in turn increase the secretion of FSH ina positive feedback.(c) The estrogen thickens the lining of the uterus in preparation for a fertilized egg.(d) The peak of estrogen secretion at day 12 causes the pituitary to release a surge ofLH. This loosens the now mature egg which is released in ovulation(e) Progesterone and estrogen together stop any more LH and FSH being secretedfrom the pituitary. (negative feedback) This prevents further follicle development orovulation.(f) Progesterone maintains the lining of the thickened endometrium in preparation forthe implantation of a fertilized egg.(g) If implantation does not take place then the Corpus luteum degenerates and 10. Hormonal regulation in males Roles of testosterone in males 1. Week 7 of embryonic development, testosterone initiates the development of male genitalia. 2. Puberty: testosterone initiates the development of secondary sexual characteristics: - increase in muscle mass - increase in the length of the long bones (height) - increase in the length of the vocal cords (voice deepens) - spermatogenesis - growth of the penis and testis 3. Post puberty testosterone maintains the production of sperm 11. In Vitro Fertilization (IVF) IVF is a method where the eggs are removed from theovaries to be fertilized in the laboratory. The eggs are then cultured for approx. 2 days andnights before the fertilized egg is transferred to theuterus for normal growth. At IVF the womans ovaries are stimulated to producemore and bigger eggs than at a normal cycle. Thismeans that more than one egg can be removed forthe treatment. More eggs improve the probability offinding suitable eggs for fertilization. IVF treatment is recommended in those cases wherethe woman has tubal blockage, the man has a poorsperm quality, or the cause of infertility is unexplained.There are a number of different medications for IVFtreatment, which are to be adjusted to the individualneed. 12. In Vitro Fertilization (IVF)a) FSH and LH are given to stimulate multiple egg cell releasesb) Eggs are collected from the ovariesc) Eggs are fertilized with fathers sperm in a dish or tube and its incubated.d) After incubation, viable blastocysts are selected and developed into embryose) Usually 3 embryos are selected for implantation. Usualle one or more will be successful, hence the risk for multiple pregnancyf) After a month of rest, a woman can take a pregnancy test. If it did not succeed, she can wait a few months to try again. (a) (b)(c)(d)(e) 13. IVF Treatment with in vitro fertilization implies that: The man produces sperm cells, or has spermcells that we in special cases can extract from thetesticle or from the epididymis. If the man doesnot produce sperm cells, donor sperm cells canbe used. The woman has ovulation, either by herself orthrough hormone treatment. The woman has a normal uterus. The couple has no incidence of venerealdiseases or infections. You have received genetic counseling. 14. Ethical issues associated withIVF FOR AGAINST Right to have children Risk of mother and Provide a family for fetuses of multipleradiation, chemo pregnancytherapy cancer Can be expensivepatients. Emotional cost of Medical advances failure can be highmake it safer every Does termination oftime human embryos count Unused embryos can as ending a humanbe stored (frozen) for life?later use, donated for Religious: are weresearch or as a playing God?source of stem cells 15. Natural fertilization Fertilization occurs when the egg and sperm cells fuse. When a sperm cell penetrates the egg, meiosis II is completed and the ovum is formed. Within the ovum, the nuclei of the sperm and ovum fuse, forming a diploid nucleus. This fertilized egg cell is called a zygote. 16. Human development, first trimester Approximately three weeks after fertilization, gastrulation takes place. It forms three cell layers: ectoderm, endoderm, and mesoderm. The ectoderm (outer layer) forms the outer part of the embryos skin and the central nervous system. The endoderm (inner layer) forms the digestive tract and lungs. The mesoderm (middle layer) forms most of the other organs. 17. Soon after implantation, trophoblast cells andcells from the uterus form the placenta. This structure enables nutrients and wasteproducts to be transferred between the motherand developing baby. By the end of the third month, the placenta is fullyformed and functional. In the wall of the placenta,the mothers blood and babys blood remainisolated in separate circulatory systems.