Chapter 28 Pregnancy and Development
Chapter 28 Pregnancy and Development
Pregnancy and Development
* Embryology
* 1 cell ( organism
* process :
* fertilization fusion of gametes (nuclei)
* mitosis 1 cell ( trillions
* cell specialization structure and function
* cell destination get to the right place
* gestation = 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
* fimbriae beat inward
* cilia propel ovum toward uterus
fertilization
* oocyte protected by outer corona radiata inner zona pellucida
* acrosomal reaction
* enzymes dissolve zona pellucida
* requires many acrosomes (sperm)
* cortical reaction
* blocks to polyspermy:
* Na diffuses in - depolarization (fast block)
* zonal inhibiting enzymes (slow block)
* Ca released – initiates meiosis II
* complete meiosis II
* fusion of nuclei 23 + 23 = 46 (diploid)
stages
* zygote 1st cell
* pre-embryo 1st 2 weeks
* embryo week 3 – 8 (week 1 – 8)
* fetus week 9 - birth
pre-embryonic growth
* cleavage
* mitotic divisions
* morula 16 + cells in a ball ~ day 3 100 cells ~ 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 - estrogen , progesterone
* 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
* functional by end of 3rd 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 protection collects urine
* surrounds fetus
* yolk sac future “gut” produces early blood cells
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 outer
* nervous system , epidermis
* mesoderm middle
* connective tissues, solid organs
* endoderm inner
* linings of tracts, cavities
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
* eg. turn on all genes for muscle cells
* cell environment
* cell location (cell map)
* concentration of extracellular chemicals
* induction adjacent cells
Stem Cells
* totipotent cell able to create entire organism
* zygote, early cleavage cells
* pluripotent can create all cells except trophoblast
* inner cell mass = embryonic stem cells
* multipotent can become a few different cells
* neural stem cells
* hematopoietic stem cells
* reproductive cloning create entire adult organism Dolly
* therapeutic cloning create specific tissues
fetal development
* weeks 9 – 38
* cell specialization detailed tissue organ development
* growth
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 allows myometrium activity
* Braxton-Hicks contractions false labor
* oxytocin (and prostaglandins)
* rhythmic contractions
* positive feedback more oxytocin
* pain 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
infnat
* neonatal 1st 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
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