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Chapter 28 Pregnancy and Development Pregnancy and Development • • Embryology – – 1 cell organism process : • fertilization • mitosis • cell specialization • cell destination gestation fusion of gametes (nuclei) 1 cell trillions structure and function get to the right place = pregnancy • 280 days from last menstrual cycle getting together • • 2 gametes 1 zygote sperm : vagina cervix uterus fallopian tube – it’s not easy : – acidic vagina – cervix open by estrogen ~ 24 hours – uterus : contractions ; phagocytes – fallopian tube – cilia – ~ 200 sperm make it • ovum : ovary fimbriae fallopian tube • oocyte protected by • acrosomal reaction • fimbriae beat inward • cilia propel ovum toward uterus fertilization • • • – – outer corona radiata inner zona pellucida enzymes dissolve zona pellucida requires many acrosomes (sperm) cortical reaction – – blocks to polyspermy: • Na diffuses in - depolarization • zonal inhibiting enzymes (fast block) (slow block) Ca released – initiates meiosis II complete meiosis II fusion of nuclei 23 + 23 = 46 (diploid) stages • zygote 1 cell • pre-embryo 1st 2 weeks • embryo week 3 – 8 • fetus week 9 - birth st (week 1 – 8) pre-embryonic growth • • • cleavage – – mitotic divisions morula 16 + cells in a ball 100 cells ~ day 3 ~ day 4-5 enter uterus ~ day 4 blastocyst – – – hollows in center = blastoceole trophoblast future chorion inner cell mass future embryonic disc twins • • identical – – – monozygotic twins zygote splits in two (or inner cell mass) adjacent on uterus adjacent or same placenta fraternal – – dizygotic twins 2 ovum + 2 different sperm 2 different placenta implantation • • • • • • • • day 6 – 7 ; complete by day 14 trophoblast fuses with endometrium trophoblast secretes : hCG maintains corpus luteum digestive enzymes digests endometrium cells growth factors endometrium growth (inflamm) ideal location - posterior superior uterus ectopic pregnancy • implantation not in uterus placenta • • • • • Placenta = chorion + endometrium chorion – part of trophoblast chorionic villi • fetal blood vessels • produce anti-coagulant endometrium – – maternal blood vessels lacunae blood filled spaces rd functional by end of 3 month produces estrogen , progesterone embryonic nutrition • • • • initial cytoplasm of ovum implantation enzymes dissolve uterine cells endometrium – – supply for 8 – 12 weeks fetal circulation forms week 3 - 4 placenta – – blood flow starts day 16 fully functional week 10 - 12 cross-placenta transport • • • • • nutrients – – – diffusion glucose lipids Na , K , Cl nutrients – – active transport AA Ca oxygen – diffusion fetal hemoglobin – greater affinity for O2 than adult Hb carbon dioxide diffusion wastes diffusion embryonic membranes • • • • from original zygote, but not part of embryo chorion fetal part of placenta amnion fluid filled sac – amniotic fluid – surrounds fetus protection collects urine future “gut” produces early blood cells yolk sac tests • • • • hCG pregnancy test Chorionic Villi sampling – – – CVS biopsy of chorionic villi embryonic cells - not part of embryo ~ 8+ weeks amniocentesis – – – amniotic fluid fetal cells 16 – 18 weeks ultrasound gastrulation • • • • • • = formation of 3 primary germ layers primitive streak 3 primary germ layers ectoderm – nervous system , epidermis mesoderm – middle connective tissues, solid organs endoderm – outer linings of tracts, cavities inner end of embryonic stage • • • • • • • • ~ 1 inch all organs and tissues formed most are functioning heart beats since week 3 ½ brain waves recorded since week 7 vascular system complete limbs and digits present able to read, change TV channels, use CD player, iPod How does this happen ? • toolkit genes control development > 5% of genome • cell differentiation turn on / off genes make different proteins • • • • – transcription factors cytoplasmic determinants master genes turn on tissue specific genes cell environment – – cell location (cell map) concentration of extracellular chemicals induction adjacent cells Stem Cells • • • • • • totipotent – pluripotent – inner cell mass multipotent – – cell able to create entire organism zygote, early cleavage cells can create all cells except trophoblast = embryonic stem cells can become a few different cells neural stem cells hematopoietic stem cells unipotent basal cells reproductive cloning create entire adult organism therapeutic cloning create specific tissues cancer as a stem cell problem • mitosis problem – – unresponsive to braking signals (growth limiters) telomeres • anaplasia • histogenic assumption • – – – failure to differentiate multipotent don’t differentiate to adult cells adult cells lose differentiation become cancerous cells probably doesn’t occur angiogenesis stim vascular growth ( as in normal development) fetal development • • • weeks 9 – 38 cell specialization detailed tissue organ development growth metabolic changes - mother • • • hPL human placental lactogen – – – – mammary development glucose-sparing gestational diabetes effect of mother’s glucose levels on fetus’ insulin hCT human chorionic thyrotropin – like TSH relaxin – relaxes pubic symphysis, pelvic ligaments and muscles physiologic changes - mother • • • • • • • • morning sickness hi estrogen, progesterone polyuria urinating for 2 stress incontinence pressure on urinary bladder hyperglycemia cortisol effect cardiovascular increase blood volume > 25% increase BP increase CO increased BMR ~ hCT varicose veins decrease venous return from LE respiration increased rate ~ hPL hormones • • • • • hCG = human chorionic gonadotropin estrogen + progesterone inhibit ovulation estrogen placenta, mammary ducts progesterone placenta, mammary glands inhibit myometrium oxytocin uterus contractions parturition = birth • • • estrogen – – – oxytocin receptors progesterone Braxton-Hicks contractions false labor oxytocin – – allows myometrium activity (and prostaglandins) rhythmic contractions positive feedback pain more oxytocin stretch of cervix hypoxia of uterus (vasospasm) stages of labor • • • stage 1 – – – – dilation 1 cm - 10 cm hours to day + cervix effaces (thins) amnion bursts stage 2 – – expulsion ~ 50 min crowning baby’s head at vulva stage 3 – – placental (afterbirth) uterine contractions detach blood vessels / placenta 15 – 20 min after baby infant • • st neonatal 1 4 weeks umbilical cord cut – – – – CO2 - central acidosis CNS stim respiration inhalation - pulmonary circulation L atrium pressure closes foramen ovale and ductus arteriosus Apgar score 0 – 10 healthy = 8 - 10