preg & human dev

when does gestation start?

from last period, abt 280 days

how long is an oocyte fertilizable?

up to 24 hours

how long are sperm viable?

1-2 days

what do acrosomal proteins do?

break down egg’s corona radiata & zona pellucida

what happens when one sperm binds to receptors on the egg?

slow block to polyspermy: cortical reaction: zona pellucida hardens & sperm receptors clip off

ovum and sperm pronuclei fuse, creating a

zygote

process of zygote → blastocyst is

cleavage

what adheres to, digests, and implants in the endometrium

trophoblast

how long does implantation take?

abt 12 days after ovulation

what stims the corpus luteum to stay alive?

hCG produced by blastocyst

when do human chorionic gonadotropin (hCG) levels decline? why?

after four months, placenta takes over

what forms the placenta?

embryonic (chorionic villi) & maternal (endometrial decidua) tissues

superior surface of embryonic disk (epiblast) forms

amnion

the fluid-filled amnion does what?

protects embryo from physical trauma, adhesion, temp & allows movement

what develops from the hypoblast of the embryonic disk?

yolk sac

what does the yolk zac do?

formation of early blood vessels

what forms the structural basis of the umbilical cord?

allantois

what is the outermost membrane of the placenta?

chorion

what is the conversion of the epiblast from a bilaminar disc into a trilayer embryonic disc consisting of ectoderm, mesoderm, and endoderm

gastrulation: germ layer formation

blastocyst → embryonic disk, aka:

gastrula

what’s the first step of gastrulation?

formation of primitive streak

what are the embryonic membranes?

allantois, amnion, chorion, yolk sac

what does the endoderm form?

mucosa of digestive & respiratory systems

what does the ectoderm form? (including neural tube)

nervous system & epidermis of skin

what’s the first event of organogenesis?

neurulation: producing brain & spinal chord

what does the mesoderm form?

all other organ systems & tissues

what does the mesoderm turn into?

notochord, paired somites (vertebrae), & paired masses of intermediate and lateral plate mesoderm

what brings blood supply into embryo?

umbilical vein

what does the ductus venosus do?

allows most of blood to bypass liver

what are the two fetal pulmonary shunts?

foramen ovale & ductus arteriosus

when does the heart start pumping blood?

by 3.5 weeks

all organ systems are laid down by the end of the ___ period

embryonic

how much does the conceptus grow during the fetal period?

from 22mm to 360mm, from less than an ounce to seven pounds+

anatomical effects of preg:

lordosis, waddling gait, weight gain: abt 28lbs

metabolic effect of preg:

human placental lactogen (hPL): growth & glucose sparring for fetus

physiological changes during preg:

constipation, dyspnea, heartburn, morning sickness, more urine (stress incontinence)

when does parturition usually occur?

abt 15 days from due date (280 days from period)

BIRTH when estrogen levels are high enough, they induce ___ receptors on myometrial cells & inhibit ___ quieting effect of uterine muscle. weak _____ start

oxytocin, progesterone, contractions

birth: fetal cells produce ____, which stim ______ production by placenta

oxytocin, prostaglandin

distension of cervix activates hypothalamus, and ____ is released from mother’s ____ (positive feedback loop for true labor)

oxytocin, posterior pituitary

what is the dilation stage?

onset of rhythmic contractions until cervix is fully dilated

full cervical dilation → birth is

expulsion stage

afterbirth is aka

placental stage

how does first inspiration occur?

umbilical chord is clamped, co2 in blood

once lungs are inflated, breathing is eased by presence of

surfactant

how long is transition? when infant is physiologically unstable & adjusting

8 hours

inflation causes pressure changes in circulation, and as a result

occluded blood vessels become fibrous cords, foramen ovale into fossa ovalis

breasts are prepped during preg for lactation by

est, prog & hpL (human placental lactogen)

premilk fluid, fat-poor, protein, vit a, minerals (produced at end of preg & for first 2-3 days after birth)

colostrum

true milk is produced on day __ in response to ___

3, suckling

suckling → hypo → anterior pituitary: ___ (milk production) & posterior pituitary: ____ (milk let-down)

prolactin, oxytocin

most-used ARTs

ivf, gift, & zift

ivf + zift: ___ gift: ____

in vitro, in vivo

what has abt 16 cells and no fluid? what has fluid?

morula, blastocyst

which system is not operational by 4-6 months?

respiratory system

what are preg tests looking for?

hCG (human chorionic gonadotropin)

what does hCG do?

maintains viability of corpus luteum until placenta takes over production of est & prog

the outer layer of the blastocyst, which later attaches to the uterus is the

trophoblast

in fetus, ductus arteriosus carries blood from

pulmonary trunk to aorta

umbilical vein carries oxygen and food to fetus / placenta?

fetus

skeletal muscles, heart & skeleton are derived from which germ layer?

mesoderm

blood cells cannot pass through placental barriers, but what can?

amino acids, antibodies, gases, & glucose

the notochord forms

nucleus pulposus (part of intervertebral discs)

sclerotome forms

ribs & vertebrae

neural tube forms

brain

placenta formation! ____ breach the uterine wall and begin reshaping bv there. these remodeled vessels become a source of maternal blood.

cytotrophoblasts

____ elaborate when touching maternal blood to form the placenta

chorionic villi

inner cell mass → extraembryonic mesoderm, mesoderm + ____ = chorion

trophoblast

two problems w breech

skull isnt a wedge to dilate cervix, not suctioned free of mucus, cant breathe in birth canal