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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