OB Ch. 10 Fetal Development and genetics Flashcards by Loren Requejo

Stages of Fetal Development

-zygotic stage
-blastocyst stage
-embryonic stage
-fetal stage

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zygotic stage

-conception
-fertilization of egg via sperm
-sperm are determiner for sex (X or Y carrier)

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fertilization occurs where

-fallopian tube
-zygote travels from fallopian tube to uterus via tubular movement

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zygote undergoes cleavage and turns into…

-MORULA
-morula reached uterine cavity 72 hours after fertilization

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Blastocyst stage

-morula cleaves and becomes more solid mass that attaches to uterine cavity
-nutrient rich fluid enters uterine cavity

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inner surface of blastocyst forms..

embryo and amnion

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trophoblast

-outer layer surrounding blastocyst
-attaches itself to endometrium for more nourishment
-will eventually attach itself to upper fundus d/t rich blood supply
-develops into chorion and helps form placenta

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embryonic stage lasts from

end of 2nd week to 8th week
-major structures and organs begin to develop, main external features

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ectoderm forms into

CNS, special senses, skin, glands, amnion

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amnion is..

thin membrane filled with amniotic fluid

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mesoderm forms…

skeletal, urinary, circulatory, and reproductive organs

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ECTODERM forms…

respiratory system, liver, pancreas, digestive

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fetal stage

differentiation and structures specialize by end of the 8th week

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role of amniotic fluid

-thermoregulation for fetus
-permits symmetric growth and development
-cushion for fetus from trauma
-allows umbilical cord to be relatively free from compression

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amniotic fluid derived from…

-fetal urine
-fluid from maternal blood source across amnion

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amniotic fluid increases in volume throughout pregnancy. By term, should be

1000 mL or 1 L

oligohydramnios

-decreased amniotic fluid
-500 mL or less
-DXed via ultrasound

what conditions are associated with oligohydramnios

-uteroplacental insufficiency
-fetal renal abnormality

Oligohydramnios: Fetus is at risk for

-low birth weight
-surgical birth

Polyhydramnios

-excess amniotic fluid
-2 L or more at birth
-DXed with ultrasound

what conditions are associated with polyhydramnios

-maternal diabetes
-neural tube defects
-chromosomal deviations
-malformations of GI or CNS

Polyhydramnios: fetus at risk for…

premature rupture of fluid membranes d/t uterine overdistention

umbilical cord characteristics

-formed from amnion
-contains 1 large vein and 2 small arteries

Wharton jelly is…

-white jelly surrounding all 3 blood vessels in umbilical cord to prevent compression
-if cord compresses, blood supply and nutrients would be cut off to fetus

Maternal uterine arteries deliver...

nutrients to placenta

Maternal uterine vein carries...

fetal waste products away

Placenta Functions

-serves as interface between mother and fetus -if something is wrong with placenta...something is wrong with fetus -produces hormones to control physiology of mother to ensure fetus is supplied with adequate nutrients and O2 for growth -placenta acts as lungs during gestation; fetal rungs are non functional -protect fetus from immune attack by the mother -remove waste products from fetus -induce mother to bring more nutrients to placenta -promotes hormones that mature into fetal organs

Placenta Characteristics

-formed by week 12 -rough side faces mother (amniotic membrane) -smooth side faces baby

Do maternal and fetal blood mix?

NO! they should not mix d/t placental barrier

what is the placental barrier

fetal tissues that separate the materal and fetal blood

Shunt does what?

-delivers oxygen rich venous blood to systemic circulation and ensures that oxygen poor venous blood bypasses pulmonary circulation

when does lung development finish?

AT BIRTH

fetal circulation pathway for oxygenated blood

-oxygen rich blood carried from placenta to fetus via umbilical vein -half goes to hepatic arteries, other half goes to ductus venosus in IVC -blood from vena cava deflected via foramen ovale into LA --> LV --> ascending aorta --> head and upper body

fetal circulation pathway for deoxygenated blood

-SVC--> RA--> RV --> pulmonary artery --> ductus arteriosus --> descending aorta --> placenta (for oxygenation) -only 5-10% of blood goes to lungs d/t pulmonary resistance b/c fetal lungs are filled with fluid and nonfunctional

what happens to lungs at birth

-with first breath, lungs inflate, leads to increase in blood flow from lungs to RV -pressure increases in LA (left side of foramen ovale presses against opening and creates functional separation between 2 atria) -blood goes to RV as it can no longer be bypassed (reason for increased blood flow to lungs) -RV pumps blood into pulmonary artery, which goes to lungs for oxygenation and back to LV