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Reproduction and Development

This detailed guide covers the intricate processes of human reproduction and development, from spermatogenesis to fetal growth stages. Learn about meiosis, differentiation, implantation, organogenesis, and fetal development milestones. Understand the stages of development, from zygote to embryo to fetus, and explore the critical milestones like implantation, organ formation, and gender development. Dive into the fascinating journey of human life creation and growth.

maynardwilliam
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Reproduction and Development

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  1. Reproduction and Development

  2. spermatogonium spermatogonium spermatogonium spermatogonium spermatogonium primary spermatocyte primary spermatocyte primary spermatocyte primary spermatocyte secondaryspermatocytes secondaryspermatocytes secondaryspermatocytes spermatids spermatids sperm Meiosis I Meiosis I Meiosis I Meiosis I Meiosis II Meiosis II Differentiation

  3. (a) HEAD nucleus tail sheath acrosome mitochondria MIDPIECE flagellum TAIL (b)

  4. egg secondary oocyte (egg) polar body primary oocyte oogonium polar body polar body polar body Meiosis I Meiosis II(after fertilization)

  5. (b) (a) ruptured follicle fimbriae fimbriae corpus luteum 4 uterine tube ovulated secondary oocyte (egg) degenerating corpus luteum ovary 3 maturefollicle with secondaryoocyte ovary uterus 2 developingfollicles 1 new folliclecontaining primary oocyte

  6. progesterone 6 LH 3 9 1 1 4 FSH estrogen 7 corpus luteum menstruation ovulation developing follicle 2 5 8 day of menstrual cycle

  7. secondary oocyte (egg) (a) corona radiata zona pellucida

  8. (b)

  9. Stages of development A. Cleavage 1. Zygote divides without an increase in size 2. A solid round ball of cells called the morula is formed 3. The morula develops a cavity producing a hollow blastula B. Gastrulation 1. Blastula cells migrate to form three tissue layers • Endoderm, ectoderm, and mesoderm 2. Resulting three-layered embryo is called the gastrula

  10. (a) (b) day 2 day 3 day 4 day 1 4 cells 2 cells blastocyst zygote day 7 fertilization embryo day 0 blastocystimplanting ovulated egg muscle layer uterine walls endometrium

  11. Human prenatal development A. Implantation of embryo in endometrium 1. Over half of all embryos fail to implant 2. hCG (human chorionic gonadotropin), basis of early pregnancy test

  12. morula stage cavity outer cell layer blastocyst (blastula stage) inner cell mass uterine lining (endometrium) embryonic disc (future embryo) yolk sac uterine lining (endometrium) amnion

  13. The opening inside the blastula is the blastocoel. yolk The blastopore is the site at whichgastrulation willbegin. (a) The blastula just before gastrulation.

  14. (e) Further development. The neural tube differentiates into brain and spinal cord. A future mouth is produced when the opening formed by the primitive gut breaks through at the end of the embryo opposite the blastopore. The blastopore is the future anus. future brain spinal cord primitivegut notochord future mouth blastopore (future anus) remnant of yolk

  15. Stages of animal development C. Organogenesis 1. Induction promotes cells to differentiate into specific organ and tissue types 2. Adult structures develop—programmed cell death a. Some cells die unless they receive a chemical "survival signal" b. Some cells live unless they receive a chemical "death signal"

  16. Human prenatal development B. Early embryonic development 1. Rapid differentiation and growth during first 2 months 2. Placenta develops a) Outer cells of blastula form the chorion, which penetrates the uterine lining and develops into the placenta b) Placenta functions 1) Secretes hormones—estrogen and progesterone 2) Regulates exchange of material between the mother and the fetus

  17. Age (weeks) 1 2 zygote to formation of embryonic disc primitivestreak Zygote cleaves;blastocyst implants Two-layered embryo forms; amniotic cavity

  18. pool ofmaternalblood fetal capillaries maternal arteriole maternal venule chorionic villi fetal umbilical vein umbilical cord fetal umbilical arteries fetal amnion fetal chorion lining of uterus (endometrium) uterine muscle

  19. Human prenatal development The Placental Barrier The placenta provides only partial protection • Smoking and pregnancy • Fetal alcohol syndrome • The impact of drugs on fetal development

  20. Age (weeks) 3 4 embryo 4 mm 2-3 mm Gastrulation occurs;notochord andbeginning of neuraltube form Neural tube closes;heart beats; arm buds,tail, and gill grooves

  21. Age (weeks) 6 5 embryo 8 mm 13 mm Incipient eye parts —retina (as optic cup) and lens (as lens pits) — form;leg buds form; brainenlarges Webbed fingers andexternal ear form;pigment appears inretina; tail and gill groovesdisappearing

  22. gill grooves 8 mm 5th week arm bud leg bud umbilical cord tail brain (a)

  23. Age (weeks) 7 8 embryo 18 mm 30 mm Upper limbs bend atelbows; genitalia beginto differentiate; fingersare distinct Webbed toes form;bones begin to harden;back straightens;eyelids form

  24. 30 mm 8th week amniotic sac umbilical cord placenta (c)

  25. Age (weeks) 9 10 fetus 50 mm 61 mm Toes separate; eyelids develop; major parts ofbrain are present Chin grows; nostrilsseparate; face appearshuman; genitals appearmale or female

  26. Human prenatal development C. Fetal development 1. After two months, the major organs have formed and the human form appears 2. Gender development in the third month 3. Last 7 months—protected growth and development period

  27. Age (weeks) 11 12 fetus 73 mm 87 mm Well-defined neck appears; genitalia arecomplete; sucking reflex appears

  28. Age (months) 4 5 fetus 140 mm 190 mm Blood cells form; all major organs form; head andbody hair appear; movements are felt by mother

  29. Age (months) 6 7 fetus 230 mm 270 mm Fetus may be viable if born; eyelids open; lungsand lung circulation develop; may suck thumb; fat deposited under skin

  30. Age (months) 8 9 fetus 300 mm 350 mm Fetus usually viable if born; fat deposits increase;body hair is lost; head hair is well developed; mostsenses are well developed; fetus turns head downin uterus

  31. 1 The baby is oriented head downward, facing the mother’s side. The cervix isbeginning to thin and expand in diameter (dilate). 4 The baby has rotated to the sideonce again as theshoulders emerge. 2 The cervix is completely dilated to 10 centimeters (almost 4 incheswide), and the baby’s head has entered the vagina, or birth canal.The baby has rotated to face the mother’s back. 3 The baby’s headis emerging.

  32. Methods of contraception 1. Abstinence—100% effective 2. Permanent contraception a. Sterilization 1) Vasectomy Tubal ligation 3. Temporary contraception a. Preventing ovulation 1) Birth control pills a) High doses of estrogen/progesterone prevent ovulation b) Extended use—Norplant and Depo-provera b. Preventing sperm and egg union 1) Condoms (male and female) 2) Diaphragm and spermicide 3) Rhythm method (natural family planning) c. Preventing implantation of fertilized eggs 1) Intrauterine device (IUD) 4. Abortion a. Partial birth abortions b. Chemically induced abortion—RU-486, methotrexate Birth Control

  33. Sexually transmitted diseases (STDs) • A. STD statistics (United States) • 1. One in five infected • 2. 12 million new STD infections per year • 3. Two-thirds of all infections in people under 25 years old, one-fourth of all infections in teenagers

  34. Sexually transmitted diseases B. Bacterial STDs 1. Gonorrhea (Neisseria gonorrheae) a. Infects 2 million per year (United States) b. No immunity to repeat infections • Can result in sterility 2. Syphilis (Treponema pallidum) a. 43,000 cases in 1995 (United States) b. Untreated can result in organ and CNS destruction • Tuskegee Experiment—1932, Macon County, Ga. 3. Chlamydia (Chlamydia trachomatis) a. Most prevalent of all STDs—over 5 million per year infected (United States) b. Serious reproductive tract complications in women - Sterility and ectopic pregnancy c. A "stealth" infection—50% of infected are completely asymptomatic

  35. Sexually transmitted diseases C. Viral STDs 1. Genital herpes a. 44 million Americans infected (1 in 5 over 13 years old, United States) b. No cure, lasts for life c. Transmitted to infants, causes severe disabilities d. Increases risk of AIDS 2. Genital warts a. Human papilloma virus b. 40 million Americans infected c. 90% of cervical carcinomas caused by HPV 3. AIDS (acquired immunodeficiency syndrome) a. 4 million diagnosed AIDS cases in past 15 years (worldwide) 1) 400,000 diagnosed infections (United States), possibly 800,000 infected

  36. Sexual disorders • A. Infertility • 1. One in six couples unable to conceive • 2. STD infections (PID) main cause of infertility • 3. Reproductive technologies • a. In vitro fertilization—26,000 test tube babies • b. Fertility drugs and multiple births

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