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A&P - Ch 28

Pregnancy & Human Development

events that occur from fertilization until birth pregnancy
time from last menstrual period until birth gestation period
developing offspring conceptus
conceptus from fertilization through 8th week embryo
conceptus from 9th week through birth fetus
oocyte is viable for up to __ hours after ovulation 24
sperm is viable up to __ hours 24-48
for fertilization to occur, coitus must occur no more than __ days before ovulation & no later than __ day after ovulation 2; 1
when a sperm fuses with an egg to form a zygote fertilization
sperm are conducted up uterine tubes by peristalsis
sperm have __ __ for the chemical signals produced by oocytes, directing sperm to them olfactory receptors
investing layer of radially elongated follicle cells surrounding the zona pellucida corona radiata
transparent, non-cellular secreted layer surrounding an oocyte zona pellucida
corona radiata are __ cells granulosa
sperm __ corona radiata penetrates
hundreds of sperm __ __ to digest zona pellucida release enzymes
pattern of various chemical changes that occur in anterior of head of spermatozoon in response to contact w/ovum & that lead to sperm's penetration & fertilization of ovum acrosomal reaction
hundreds of acrosomes must undergo exocytosis to digest holes in zona pellucida
actin filaments in sperm head form __ __ that quickly finds & binds oocyte's sperm-binding membrane acrosomal process
binding event of sperm & oocyte causes oocyte & sperm membranes to fuse
binding event of sperm & oocyte causes contents of sperm to enter oocyte cytoplasm
haploid nucleus (of ovum/sperm) occurring after meiosis in a germ cell pronuclei
as sperm enter oocyte it looses its tail
upon entry of sperm, 2ndary oocytes completes meiosis II
when the pronuclei __ __ fertilization occurs come together
maternal & paternal chromosomes Combine to produce diploid zygote
fertilization in which only one spermatozoon enters the oocyte monospermy
entrance of more than one spermatozoon into the ovum polyspermy
almost as soon as male & female pronuclei come together their chromosomes replicated
once chromosome replication takes place zygote ready to undergo 1st mitotic division of conceptus
period of fairly rapid mitotic division of zygote without intervening growth cleavage
zygote begins to divide 24 hours after fertilization
zygote continues __ __ as it travels down uterine tube mitotic divisions
mulberry-like solid mass of blastomeres resulting from cleavage in the early conceptus; made of 16/more cells (3days) morula
stage of early embryonic development; the product of cleavage; ball of 100/ so cells hollows out, fills with fluid (day 4)- floats free in uterine cavity for 3d early blastocyst
peripheral cells of blastocyst, which attach blastocyst to uterine wall & become placenta & membranes that nourish & protect developing organism trophoblast cells
accumulation of cells in blastocyst from which embryo develops inner cell mass
fluid-filled hollow sphere composed of outer sphere of single layer of trophoblasts cells & inner cell mass late blastocyst
inner cell mass will become embryo
attachment of blastocyst to epithelial lining of uterus, its penetration through epithelium, &, in humans, its embedding in stratum compactum of endometrium, occurring 6/7 days after fertilization of oocyte implantation
cellular (inner) layer of the trophoblast; cells retain boundaries cytotrophoblast
outer syncytial layer of the trophoblast; invades endometrium & rapidly digests uterine cells it contacts syncytiotrophoblast
blastocyst burrows into endometrium & gets covered over & sealed off by proliferating endometrial cells
implantation is completed by 12th day after ovulation
implantation of blastocyst anywhere other than the uterus ectopic
tubal pregnancy risk factor scarring of uterine tube by prior tubal infection, adhesion due to previous surgery, clinical features
secreted by the trophoblast cells; viability of corpus luteum is maintained by human chorionic gonadotropin hormone (hCG)
hCG acts like LH
signaled by hCG, corpus luteum continues to secrete progesterone & estrogen
antibody tests that detect hCG pregnancy tests
after 12th week __ takes over production of estrogen & progesterone for rest of pregnancy placenta
maternal endometrial tissues & embryonic trophoblastic tissues form placenta
trophoblastic cords from blastocyst invade the endometrium to form finger-like chorionic villi
grow into chorionic villi from vascular system of newly forming embryo blood capillaries
supplied with blood from mother develop between the villi maternal blood sinuses
placenta is fully formed and functional by third month
lowing through two umbilical arteries into capillaries of villi fetal blood
after exchange with blood in maternal sinuses fetal blood flows back to fetus in single umbilical vein
nutrients & oxygen __ from maternal sinuses into fetal blood diffuse
fetal excretory products __ to maternal blood diffuse
inner cell mass forms two layered embryonic disc
during occurrence of implantation, 3 germ cell layers are forming from bi-layered embryonic disc
during occurrence of implantation, extra __ __ develop embryonic membranes
sac of transparent membrane filled w/amniotic fluid amnion
sac on the ventral surface of the embryo yolk sac
yolk sac produces earliest blood cells & vessels
yolk sac later forms part of digestive tube
out-pocketing of the yolk sac allantois
allantois is __ __ for umbilical cord structural base
helps form placenta; encloses embryonic body & all other membranes chorion
during the 3rd week, the two-layered embryonic disc becomes a three-layered embryo gastrulation
gastrulation begins when primitive streak appears
raised dorsal groove that forms longitudinal axis of embryo primitive streak
ectoderm, mesoderm, and endoderm are primary germ layers
rod of mesodermal cells that serves as first axial support notochord
forms structures of nervous system and epidermis of skin ectoderm
forms epithelial linings of the digestive, respiratory, and urogenital systems, liver, pancreas endoderm
forms muscle, cartilage, bone, blood & other connective tissues mesoderm
formation of body organs organogenesis
gastrulation sets stage for organogenesis
all organ systems are recognizable & embryo is 22mm long (crown rump length) end of embryonic period 8th wk
ectoderm forms __ __ which will become the brain & the spinal cord neural tube
epidermis of skin, lens of eye, enamel of teeth are of ectoderm origin
endoderm forms the primitive gut
primitive gut forms epithelial lining of GI tract
primitive gut forms associated organs thyroid, liver, pancreas
primitive gut forms epithelium linings of respiratory tracts
vertebrae and ribs, dermis of the skin, skeletal muscles, gonads and kidneys, other bones, heart & blood vessels, smooth muscle & other CT are derivatives of mesoderm
unique cardiovascular modifications seen in prenatal development include umbilical arteries & veins, & 3 vascular shunts (occluded at birth)
venous shunt that bypasses liver ductus venosus
opening in the septum btwn two atria foramen ovale
transfers blood from right ventricle to aorta ductus arteriosus
fetal cardiovascular system is formed in embryonic period
carries nutrients & oxygen from placenta to the embryo umbilical vein
return oxygen poor waste laden blood to the placenta pair of umbilical arteries
ductus venosus is a shunt that allows most of blood to bypass liver
foramen ovale & ductus arteriosus allow most of blood to bypass lungs
especially dangerous during embryonic period; may cause severe congenital abnormalities or fetal death; include alcohol, nicotine, some drugs, German measles teratogens
causes growth retardation, developmental delays, microcephaly, mental retardation fetal alcohol syndrome
all organ systems laid down; webbed digits now free; ossification begun; CVS is functional; CR length- 22mm 8th week
heart is pumping blood since 4th week
body elongating; crude facial features; blood cell formation begins in bone marrow; sex easily detected; CR length 90mm 9th week
blinking of eyes- bones distinct; CR length 140mm 13-16 weeks
vernix caseosa covers body; fetal position assumed- quickening- CR length; 190mm 17-20 weeks
may survive if born premature, but lung surfactant is inadequate; CR length 280mm 21-30 weeks
testis descends in scrotum in 7th month
CR length- 360mm 30-40 weeks
common anatomical change during pregnancy lordosis
typical weight gain is about 29 pounds
during pregnancy females' pelvic ligaments & pubic symphysis relax
during pregnancy common anatomical change is __ expands till it occupies most of abdominal cavity uterus
during pregnancy a metabolic change is that females are in state of hypermetabolism
during pregnancy a metabolic change is maternal cells use more __ __ & less __, sparing it for the fetus fatty acids; glucose
common metabolic disorder in pregnant women gestational diabetes
during pregnancy physiological occurrence in GI tract, due to elevated estrogen & progesterone morning sickness
during pregnancy physiological occurrence in urinary system, in which __ __ increases to handle the additional fetal wastes, frequency urine production
during pregnancy physiological occurrence in urinary system, which affects respiratory system developing late in the pregnancy dyspnea/difficulty breathing
during pregnancy physiological occurrence in cardiovascular system blood volume & pressure increases
series of events that expel infant from uterus labor
parturition birth
occurs during last weeks of pregnancy causing myometrium to become more sensitive to oxytocin estrogen reaches a peak
weak irregular contractions that may occur; false labor Braxton Hicks
as birth nears __ & __ start rhythmic uterine contractions oxytocin; prostaglandins
the more the uterus contracts, the more oxytocin is released due to a(n) positive feedback mechanism
the more oxytocin is released, the __ __ are, ending in birth strong contractions
stage 1 of labor dilation
stage 2 of labor expulsion
stage 3 of labor placental
dilation stage lasts from onset of labor until cervix is fully dilated
during dilation stage initial contractions are weak but irregular
during dilation stage, as contraction become more rapid & prolonged cervix undergoes effacement
effacement is thinning & dilating of cervix
during dilation stage, __ ruptures, releasing amniotic fluid amnion
during dilation stage, baby's head enters true pelvis
when baby enters true pelvis engagement
during dilation stage, as descent occurs through birth canal baby's head rotates
the dilation stage lasts for 6-12 hours
at 10 cm the cervix is fully dilated
during dilation stage, the widest head dimension is in left to right axis
during dilation stage, after rotation the widest head dimension is in anteroposterior axis
from full dilation to delivery of infant expulsion stage
during expulsion stage, __ __ occur every 2–3 minutes and last about 1 minute strong contractions
during expulsion stage, __ __ __ increases urge to push
during expulsion stage, __ occurs birth
crowning occurs during expulsion stage
expulsion stage lasts from 1- 2hours
when largest dimension of head is distending vulva crowning
delivery of placenta & attached fetal membranes afterbirth
afterbirth is accomplished within 30min of birth
afterbirth is delivered during placental stage
during placental stage, continued uterine contractions detach placenta off uterine wall
during placental stage, all placenta fragments must be removed to prevent postpartum hemorrhage
Immediately after birth, infant’s physical status is assessed based on heart rate, respiration, color, muscle tone, & reflexes
total score of heart rate, respiration, color, muscle tone, & reflexes Apgar Score
each observation under Apgar Score is given a score of 0 to 2
8-10 Apgar Score indicates healthy baby
lower than 8-10 Apgar Score may reveal problems with baby
once carbon dioxide is no longer removed by placenta it accumulates in baby’s blood
accumulation of CO2 in baby's blood excites respiratory centers in brain stem to trigger first inspiration
when infant is born lung are collapsed so 1st inspiration takes tremendous effort
once infant's lungs inflate, __ __ __ helps reduce surface tension, breathing is easier surfactant in alveoli
after birth, the special umbilical __ & __ are not required vessels; shunts
after birth, changes that occur to umbilical arteries distal parts become fibrosed as umbilical ligaments
after birth, changes that occur to umbilical vein becomes round ligament of liver
after birth, changes that occur to ductus venosus becomes ligamentum venosum
after birth, changes that occur to foramen ovale becomes fossa ovalis
after birth, changes that occur to ductus arteriosus becomes ligamentum arteriosum
toward end of pregnancy estrogen, progesterone, & human placental lactogen stimulate hypothalamus to release prolactin-releasing hormone (PRH)
responds to PRH by releasing prolactin which causes milk production anterior pituitary
released the first 2–3 days; rich in vitamin A, protein, minerals, & IgA antibodies colostrum
baby’s suckling causing release of oxytocin; which causes milk ejection milk let down
fluid-filled, hollow ball of cells blastocyst
fetus begins at week nine
has three primary germ layers and embryonic membranes gastrula
morula berry-shaped cluster of 16 or more cells
zygote single-celled embryo
bones form from mesoderm
brain forms from ectoderm
liver forms from endoderm
ductus arteriosus functions to allow blood to bypass the lungs
ductus venosus functions to allow blood to bypass liver
ligamentum venosum is remnant of venous shunt that bypassed liver
ligamentum arteriosus is remnant of vessel that connected pulmonary artery to aorta in fetus
umbilical cord functions to carry blood to & from placenta
function of foramen ovale connects right atrium to left atrium
fossa ovalis is depression on wall of atrial septum
umbilical artery carries __ concentration of oxygen highest
umbilical vein carries __ concentration of oxygen medium
estrogen rises throughout pregnancy
hCG lets the corpus luteum know you are pregnant
oxytocin causes contraction of uterus near end of pregnancy
relaxin causes pelvic ligaments & pubic symphysis to become more flexible
occurs on day 14 of average menstrual cycle ovulation
day 21 of average menstrual cycle implantation begins
forms embryo proper inner cell mass
forms chorion of placenta trophoblast
third week embryo
occurs within one day after ovulation fertilization
at end of 8th week fingers and toes formed
nine to 12 weeks sex detectable by genitals
13-16weeks most bones distinct and joint cavities apparent
17-20 weeks mother feels fetal muscle movements
7th month testes reach scrotum in males
8-9th month fat laid down in subcutaneous tissue
after fertilization the zygote goes through a rapid period of cell divisions called cleavage
implantation is usually completed after blastocyst is entirely surrounded by endometrium
chorion is outermost embryonic membrane
gastrulation process that transforms the embryo into a three-layered stage
brain formed from ectodermal tissues
function of the ductus arteriosus bypass the pulmonary circuit
oxytocin hormone that induces labor and controls labor via a positive feedback mechanism
dilation, expulsion, placental correct order of the stages of labor
fossa ovalis structure represents remnants of atrial fetal shunt
signals corpus luteum to continue producing estrogen & progesterone to maintain pregnancy function of the hormone hCG (human chorionic gonadotropin)
heart begins to beat in developing offspring at 3-4 weeks
implantation of the blastocyst begins 6-7 days after ovulation
milk production by the breast tissue is caused by prolactin
newborn's source of energy for the first few days fat
disc-shaped placenta is formed from chronic villi & decidua basalis
gastrulation process by which three primary germ layers form
first major event of organogenesis neurulation
cleavage produces sphere of very small cells
placenta forms from chorion & endometrium
hCG begins to __ after week 8 decline
placenta is __ __ for embryo & fetus nutritive agent
neurulation is differentiation of the ectoderm
early ventral body cavity forms from folding of embryonic body
chorionic villi membrane & endothelium of fetal capillaries separate mother & fetal blood supplies
when blood leaves fetal heart only part of it will pass to placenta before returning to heart again
ductus arteriosus allows fetal blood to __ lungs bypass
occurs eight weeks into pregnancy head of fetus is nearly as large as body
occurs 17-20 weeks into pregnancy, during the fetal period quickening
__ & __ are hormones & powerful uterine muscle stimulants which cause contractions to become more frequent & more vigorous oxytocin; prostaglandins
woman has deformed/male-like pelvis, resulting in prolonged & difficult labor; condition can lead to fetal brain damage, ultimately causing cerebral palsy/epilepsy dystocia
Created by: lfrancois



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