Pregnancy and human_development

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Pregnancy and human_development

  1. 1. PREGNANCY & HUMAN DEVELOPMENT
  2. 2. Fertilization oocyte viable 12 - 24 after ovulation sperm retain fertilizing power within female reproductive tract 12 - 48 hours some “super sperm” viable for 72 hours about 5 days a month that pregnancy can occur
  3. 3. Sperm Transport acidity within the vagina is hostile to sperm & some leak from vagina or die almost immediately many cannot penetrate cervical mucus in uterus thousands are killed by leukocytes only a few thousand finally reach uterine tubes
  4. 4. Capacitation membranes must become fragile so that hydrolytic enzymes in their acrosomes can be released
  5. 5. Acrosomal Reaction acrosomal reaction: release of acrosomal enzymes that occurs in immediate vicinity of oocyte hundreds of acrosomes must rupture to break down intercellular cement of oocyte single sperm makes contact with oocyte
  6. 6. Sperm Penetration nucleus is pulled into oocyte cytoplasm only one sperm is allowed to penetrate Fusion of nuclear material occurs to complete fertilization
  7. 7. Preembryonic Development fertilized egg is now called a zygote
  8. 8. 1. Cleavage & BlastocystFormation cleavage: period of rapid mitotic divisions following fertilization daughter cells become smaller & smaller results in a high surface-to-volume ratio for greater uptake of oxygen & nutrients
  9. 9. blastomeres: – 2 identical cells by 36 hours – 4 identical cells by 60 hours – 8 identical cells by 72 hoursmorula: berry-shaped – 100 cell 4-5 days
  10. 10. Implantation 6 days after ovulation implantation begins completed by 14 day 1
  11. 11. Placentationformation of placentahighly vascularfully functional as nutritive, respiratory,excretory, & endocrine organ by end of2nd month of pregnancysome harmful substances can passplacental barriers 1
  12. 12. teratogens: may cause severecongenital abnormalities or even fetaldeath – alcohol, nicotine, drugs, infections 1
  13. 13. Events of Embryonic Development 1
  14. 14. Formation & Roles ofEmbryonic Membranes amnion: sac that becomes filled with amniotic fluid which bathes cells – provides buoyant environment & protection against physical trauma – helps maintain temperature – as kidneys develop urine is added to fluid – water portion is exchanged 3 hours 1
  15. 15. yolk sac: blood cell formation &produce gonadschorion: forms placentaallantois: constructs umbilical cord – becomes part of bladder 1
  16. 16. Gastrulation: Germ LayerFormation Ectoderm Mesoderm Endoderm 1
  17. 17. Ectodermall nervous tissueskin, hairs, sebaceous & sweat glands,& nailstooth enamelepithelium of: oral & nasal cavities,anal canal, pineal & pituitary glands 1
  18. 18. Mesodermskeletal, smooth, & cardiac musclecartilage, bone & other CTblood, bone marrow, lymph tissueureters, kidneys, gonads 1
  19. 19. Endoderm epithelium of digestive tract liver, pancreas thyroid, parathyroid, & thymus glands 1
  20. 20. Effects of Pregnancy on Mother 2
  21. 21. Anatomical Changes breasts enlarge & areolae darken “mask of pregnancy” pigmentation of facial skin uterus enlarges lordosis placenta produces the hormone relaxin, that causes ligaments to relax & become flexible for child birth weight gain about 25 lbs 2
  22. 22. Gastrointestinal System excessive salivation morning sickness: increase of hormones heartburn: esophagus & stomach is crowded constipation: motility of digestive tract declines 2
  23. 23. Urinary Systemurination more frequent & sometimesuncontrollableuterus compresses bladderkidneys also have to dispose of fetalwastes 2
  24. 24. Respiratory System lung volume decreases nasal stuffiness 2
  25. 25. Cardiovascular System total body water rises as safeguard against blood lose during birth blood volume increases 25 - 40 % blood pressure & pulse rise uterus presses on pelvic blood vessels, venous return from lower limbs may be impaired & result in varicose veins 2
  26. 26. ParturitionBirth 280 days after conception 2
  27. 27. Initiation of Labor last few weeks of pregnancy estrogen reaches highest levels myometrium becomes increasingly irritable & weak which may cause Braxton Hicks contractions or false labor oxytocin is released by posterior pituitary which causes expulsive contraction of true labor 2
  28. 28. Stages of Labor 2
  29. 29. Dilation time from labor’s onset until cervix is fully dilated (10 cm) contractions begin in upper part of uterus & move downward toward vagina contractions 15 - 30 minutes apart & last for 10 - 30 sec. contractions become more vigorous & rapid 2
  30. 30. infant’s head is forced against cervixcausing it to soften & become thinneramniotic fluid breakslasts 6-12 hours 3
  31. 31. Expulsion from full dilation to delivery contraction every 2 - 3 minutes & lasting 1 minute lasts 20 minutes to 2 hours crowning episiotomy may be performed to reduce tearing umbilical cord is clamped & cut 3
  32. 32. Placental delivery of placenta within 15 minutes of birth important that all placental fragments be removed called afterbirth 3

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