CH. 12 Fetal development: Notes Flashcards
developing embryo is known as
blastocyst
ova and sperm =?
zygote
Fertilization location= ?
ampulla of Fallopian tubes
X chromosome from mom, what from dad
x or y
6-10 days after fertilization
implantation, blastocyst burrows into endometrium
outer layer of blastocyst that develops into chorionic villi
trophoblast
length of pregnancy
280 days / 40 weeks
establishment of germ layers occurs
during pre embryonic or ovum stage/ day 1-14
primary germ layers
ectoderm, mesoderm, endoderm
all tissues and organs develop from
germ layers
chorion covers
fetal side of placenta
epidermis, glands, ant. pituitary systems, nails, hair, CNS and PNS develop from
ectoderm
bones, teeth, skeletal muscles, smooth muscle, cardiac system, GU system
mesoderm
resp, GI, liver, pancreas, urethra, bladder, vagina, and formation of roof of yolk sac
endoderm
2 fetal membranes surrounding fetus
chorion (fetal side) and amnion (mom side)
maintains constant temp for fetus, cushions the fetus from trauma, source of oral fluid and repository for waste, allows freedom of movement for development and symetric growth, acts as a barrier to infection, allows fetal lungs to develop
amniotic fluid
Too little amniotic fluid 300 cc is oligohydramnios
renal abnormalities
Too much amniotic fluid polyhydramnious(2L) can cause
GI abnormalities
Transfers oxygen and nutrients to fetus
Eventually becomes part of digestive tract
yolk sac
Wharton’s jelly function
prevents compression of vessels, ensures nourishment of embryo or fetus
placenta in place by
day 17
corpus leuteum maintains progesterone until placenta takes over, placenta develops from chorionic villi which develop into
branches of blood vessels
Umbilical cord-
3 vessels
Vein returns blood to embryo
Arteries carry blood from embryo to chorionic villi
Covered by connective tissue
Placental functions depend on
maternal blood pressure
Early function of placenta=endocrine gland produces the hormones to
maintain pregnancy
HCG reaches max level 50-70 days and then
decreases
Embryonic stage day
15 day- 8th week
most critical time in development of organs and external features, vulnerable to teratogens
Embryonic stage day 15day- 8th week
Fetal stage:
9th week to delivery
,by the end of the 8th week all organ systems and
external structures are present
stage of maturation for fetus
fetal stage
capacity of the fetus to surrvive outside the uterus
viability
first system to develop
Cardiovascular System
Tubular heart beats
4-5 weeks
cardiovascular system has special circulatory pathway which bypass lungs via
Ductos arteriosis and
Foreamen ovale
Primary surfactant present for survival at
about 32 weeks (resp system)
35 weeks is key to fetal
lung maturity
L/S ration lecithin/sphingomyelin ratio
2:1 to be mature
Two umbilical arteries
One vein which
carries oxygen rich blood back to fetus
Rhythmic breathing movements
Ability to partially control temperature
Bones are fully developed but soft and flexible
week 32 of fetal development
Surfactant=detection of pulmonary surfactant in amniotic fluid is used to determine (L/S ratio is used to determine)
FLM
Lecithin is the most critical alveolar surfactant required for
postnatal lung expansion.
Sphingomyelin is second
surfactant
At approx. 35 weeks surfactant ratio should be
2:1
conditions that decrease maternal blood such as HPTN, Placental dysfunction, infection and cortiocosteroid use causes what to FLM
accerlate FLM
Conditions that retard FLM =
gestational diabetes
Gestation is 280 after LMP or 266 after
conception
