Union of a single egg and sperm marks the beginning of antepartal period
conception usually occurs when?
within 12-24 hrs after ovulation in the outer third (ampulla) of the fallopian tube
Diploid number of chromosomes is reestablished with what?
egg and sperm united to form the single cell known as the
Implantation usally occurs when?
withing 7 days of conception, or about day 21 of a 28 day menstrual cycle
moves the first layer of the edometrium slightly and embeds in the endometrium usually in the top (fundal) portion of the uterus at about day 6-10
Implantaion occurs when entire blastocyst is cover by?
Chorionic villi extend from the blastocysts into the endometrium which is thick and vascular from progesterone) to?
gain nutrients from mother and to get rid of CO2 and waste products.
After implantation the endometrium is renamed?
During 10-14 days after conception the blastocyst differentiates into?
three primary germ layers: ectoderm, mesoderm, and endoderm.
formed at the same time as the embyonic membranes
all tissues and organ systems will develop from?
the three primary germ laters
Embryonic stage last how long?
from day 15 until 8 weeks after conception or until the embryo measures 3cm (crown-rump)
forms primitive red bloods cells during the first 6 wks of embryo development until the liver takes over the process.
provides oxygen and nutrients while uteroplacental cirulation is established
By the 3rd wk heart begins to beat and circulate blood through?
embryo, stalk, chorion, and yolk sac
yolk sac is eventually incorporated into the
Two __________ begin to develop at time of implantation
function of fetal membrane
support embryo as it grows and develops inside uterus
outer cell membrane develops from the trophoblast and contains chorionic villa on its surface (thick)
fetus may survive outside the uterus when?
currently at 27 wks after conception. possible at 20 wks post conception or 22 wks since LMP (500g fetal weight)
tubular heart begins to beat and CV system links embryo, stalk, chorion and yolk sac when?
4 chamber heart is seen when?
organ systems and external structures visible by
lungs do not function for gas exchange, therefore
we need alternative cirulatroy pathway
fetal heart is controled by
its own pacemaker
SA node sets the rate and supplied by
AV node bridges the ________ and ______ and is supplied by ________
atrium, ventricle, vagus nerve
stress on fetus causes sympathetic nervous system to release _____________, which _______the fetal heart rate.
how does the fetal heart counteract in increase in rate and blood pressure?
baroreceptors which respond to stretch and vagus nerves cause the heart to slow
Central Nervous System also controls
fetal heart rate
increase activity of fetus exhibits?
increase in beat to beat variablity of fetal heart baseline.
sleep patterns demonstrate?
decrease in beat to beat variablity of fetal heart baseline
in sever hypoxia, increase levels of epinepherine and norepinepherine act to?
make the heart faster and stronger
how commone is twins
1 in 80 pregnancies
how commone is triplets
1 in 8000 pregnancies naturally
two separate ova fertilized by two separate sperm. two placentas, two chorions, and two amnions, however placentas sometimes fuse and look like 1. no more alike than if they were born separately.
identica - monozygotic (twin)
develop from single ovum. same sex and genotype(appearance) common placenta
how long does pregnancy last?
10 lunar months; or 40 wks; or 280 days
from the beginning of the last menstrual period to the time of birth
fertilization age or post conception age of the fetus is calculated how?
more accurate why?
about 2 wks less or 266 days (38 wks)
measures fertilization of the ovum, or conception
1st 14 days of development after ovum is fertilized
rapid cell multiplication and differentiation and establishment of embryonic membranes and primary germ layers
period when tissue?
embryo is most vulnerable to ?
begins at day 15 (3rd week after conception or fertilization) and continues until 8 wkds or until embryo reaches crown0rump length of 3 cm
differentiates into essential organs
teratogens up until about the 12th wk
- at 28 days arm and leg buds become visible; tail bud present until now
- takes human form
at 4 wks tubular heart is beating a regular rhythm and?
pushing primitive blood cells throught the main vessels
5th week formations
eyes and nasal pits form
embryo looks c shaped
brain differentiated into 5 areas and 10 pairs of cranial nerves recognizable
at 6wks liver is doing?
making RBC's and fetal circulation establihed
7th week formations
eyelids form, embryo rounded and nearly erect. palate nearing completions; tongue developing
GI and GU tracts now 2 separate structures
umbilical herniation present
8th wk formations
3cm and clearly looks like a human being; eyelids fuse; auricles of ears assume shape; external genitals appear; anus formed; cirulatory system through umbilical cord established; long bones begin forming
begins at end of 8th wk
every organ system that will be found in full term newborn is present
remainder of gestation is oto refine the organ structures
at week 9 the head is how loarge?
1/2 of fetus's entire size
12 wk formations
- fetus is 3.2 inches and wighs 1.6 oz
- face is well formed
- eyelids close and will not reopen until 28 weeks
- sucking relfex observed
- tooth buds appear
- curls fingers
- legs shorter than arms
- urogenital tracts complete
- kidneys make urine
- spontaneous fetal movement occurs
- fetal heart tones hear by doppler at 11 wks
- FHR is approximately 120-160BPM
- period of rapid growth
- at 13 wks is 3.6 inches and 2oz
- lanugo develops on head
- skin transparent - can see blood vessels
- active movements are present as fetus stretches and exercises
- sucking motions, swallows amniotic fluid, and produces meconium in GI tract
- primitive lungs, sweat glands are developing
- liver and pancreas begin secretions
- skeletal ossification is identifiable
- double in C-R lenght and measures 8 inches, weighs 16-16oz
- lanugo over entire body; subcutaneous brown fat has rich blood supply makes skin less transparent
- nipples appear, head is covered with wooly hair
- muscles are developed
- fetal movement (quickening) felt by mother
- aveoli in lungs beginning to form
24 wk formations
- C-R lenght is 11.2 inches and weighs 1lb 10oz
- hair is growning long
- reflex hand grip
- little subcutaneous fat
- skin ridges on palms and soles
- skin is covered by fatty substance secreted by sebaceous glands called Vernix Caseosa
- alveoli in lungs beginning to form
- marks 6 calendar months
- fetal skin, wrinkled and covered with vernix
- brain rapidly debeloping
- nervous system complete
- nails on fingers and toes
- eyelids open and close per nueral control
- lungs, although immatrue provide some gas exchange
- 14-15 inches long and 2lbs 20oz02lbs 12oz
- can survive outside womb with intensive care
- pupillary light reflex +
- gaining weight period
- lungs not fully matrue but CNS regulates breathing movements and partially controls body temperature
- testicles located in scrotal sac in some fetuses
weighs 4 lbs 6 oz and is 15-17 inches long
- gets fat stores and less wrinkled with more subcutaneous fat deposits present
- lanuga disappears slowly
- nails reach edge of fingertips
firm grasp and spontaneous orientation to light
weights 51/2 to 6 lbs and is 16-19 inches long
good chance of surving by may require some special care
lungs not fully matured yet
considered full term at 38 wks after conception; 40 wks per calendar method
lenght should be between 18-21 inches long with males longer than females
weight @term is 6lbs 10 oz to 7lbs15oz
- skin polished look
- lanugo on shoulder upper arms only
- vernix caseosa present in creases and folds of skin
- chest smller than head
- assumes positionor lie in pelvis
- after 5 months already has established feeding pattersk, leeping patterns, activity patterns
factors influencing embryonic and fetal development
- quality of sperm or ovum from which zygote was formed
- genetic code established at fertizlization
- adequacy of itrauterine environment
- after differentiation is complete the fetal membrans are fromed and an injuious agent has the greates effect on those cells undergoing the most rapid period of growth
- maternal nutrition can affect brain development and disease
- primary nutries for brain development are amino acids, glucose and fatty acids