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Reproduction & Development

Reproduction & Development. Fertilization: Sperm. 200-500million haploid sperm cells swim to uterine tube 30 min-2hrs only 10,000 sperm reach the uterine tube Live for up to 48 hours waiting for oocyte (egg)…only 100 reach the oocyte Acrosome cap w/enzymes Flagellum falls off once enters egg.

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Reproduction & Development

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  1. Reproduction & Development

  2. Fertilization: Sperm • 200-500million haploid sperm cells swim to uterine tube • 30 min-2hrs only 10,000 sperm reach the uterine tube • Live for up to 48 hours waiting for oocyte (egg)…only 100 reach the oocyte • Acrosome cap w/enzymes • Flagellum falls off once enters egg

  3. Fertilization: Oocyte • Oocyte 2000x larger than sperm • Found in upper 1/3 of uterine tube w/in one day if ovulation • Several sperm required to penetrate corona radiata • Only one sperm can penetrate the zona pellucida • Then enzymes prevent other sperm from entering • This activates oocyte to complete meiosis

  4. Gestation: Prenatal Development • Cleavage • (day 1-6) • mitotic cell divisions as travels down uterine tube • w/in 30hrs zygote divides to form blastomeres • Blastomeres divide every 10-12 hrs • Day 3 – morula – solid ball of cells • Day 5-6 blastocyst – hollow ball of cells, cells begin to differentiate

  5. Gestation: Implantation • Implantation • Day 7-10: blastocyst adheres to uterine lining • Days 10-12: differentiation continues to form Amniotic cavity, Yolk sac (blood cell formation), and germ layers • Germ layers: • Endoderm • Mesoderm • Ectoderm

  6. Gestation: Placentation • Placenta – allows diffusion between fetal and maternal circulation (blood barrier) • By week 3 – Placenta begins to form • Produces hCG – prevents mensus • By week 4 – yolk sac shrinks and fuses into umbilical cord • By week 10-12 – placenta produces estrogens and progesterone, ovaries become non functional

  7. Embryonic development 3-4 weeks Neural tube begins 5 weeks 2mm “c” shaped Heart bulge Functional yolk sac & placenta 6-7 weeks .5” (tadpole w/gills slits) Heart beats Neural tube closes Arm & leg buds Lungs, nostrils, lenses, and dig tract forms 8-10 weeks 1” Muscles – 1st movements Ovaries/testes form Fingers/toes, ears/lips develop Bones ossify 11-13 weeks (Fetus) 2-3” Nails, vocal chords, kidneys (urine), and ears Reflexes, hiccups (diaphragm), rollover, stretch Pancreas, gall bladder, wbc Maternal Development Fatigue Morning sickness Tender breasts Decreased bp, lightheaded & dizzy Blood volume increases Require 10-30% more nutrients and vitamins Frequent urination First Trimester

  8. Fetal Development 14-18 wks 4-6” (lobster tail) Fingerprints, auditory ossicles, teeth, hair & eyebrows Make faces, eyes move & detect light Suck thumb 19-22 wks 8-10” (small grapefruit) Taste buds, sense touch, and stress Perm teeth Myelination of ns L/R handed Ovaries produce eggs 23-27 wks 11-15”, 2lbs (bag coffee) Recognize voices and respond Fat deposited Skin pigmented Adv. brain functions Maternal Development 90% chance full term Incr. mucosal secretions Increase breast size Pelvis spreads Pressure on organs Feel baby move Indigestion & heartburn By end: others can feel baby Second Trimester

  9. Fetal Development 28-31 wks 15-16”, 3.5 lbs Fully developed (except brain, lungs, liver) Movements increase 32-36 wks 17-20”, 5lbs Synapse brain & nerves Head down position Adding fat 37-40 wks 21-23”, 6-10lbs Testes descend into scrotum Receiving antibodies When ready: placenta incr. estrogen, increases oxytocin, stim contractions Contractions start at top uterus and spread Moves lower back into pelvis Maternal Development Back pain Swelling Itchy skin Hemorrhoids High bp Visible kicks/punches Increase in relaxin production Third Trimester

  10. Labor & Delivery • Dilation • avg 15 hrs • Cervix dilates • Contractions 10 – 30 minutes • Amnion ruptures - “water breaks” • Parturition: expulsion of fetus • Less than 2 hrs • Cervix pushed open by fetus • Full dilation 10 cm • If canal is too small – Dr performs episiotomy • Placental After-birth • Less than 1 hr • Muscle tension in uterus and shrinking of uterus tears placenta away from uterine wall, placenta is ejected (blood loss)

  11. Premature Labor • < 14 oz – underdeveloped, no chance of survival • Between 25-27 weeks – may survive, but with developmental abnormalities • 28-36 weeks - survival w/normal development

  12. Multiples • 1/89 Twins • 70% dizygotic – “fraternal” 2 eggs fertilized at the same time • 30% monozygotic – “identical” splitting of blastomere • Conjoined twins - incomplete splitting of blastomere (share skin, liver, other organs) • 1/7921 triplets

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