Pregnancy & Human Development

how long is the secondary ooctye viable after ovulation

12-24 hrs

when the sperm's chromosomes combine with those of

an ovum to form a fertilized egg (zygote)

fertilzation

enzyme of sperm cell surface that digests the granulosa cells of the corona radiata (arround oocyte)

hyaluronidase

enzymes from what digest holes into the zona pellucida

acrosome

binding of sperm to oocyte membrane causes what reaction?

cortical reaction = Ca2+ surge within oocyte --> granules reasease ZIPs & hardening of zona pellucida --> destruction of sperm-binding receptor = prevent polyspermy

Zonal inhibiting proteins

ZIPs - prevent polypermy

sperm contents to enter the oocyte via .....

sperm and oocyte plasma membranes fusion

The Ca2+ surge from sperm entry triggers completion of

meiosis II

is a zygote diploid or haploid?

Diploid because it contains TWO haploid sets of chromosomes from maternal and paternal family lines

When does implantation happen?

6-7 days after ovulation

what adheres to a site on the endometrium to signal the implantation site?

trophoblast

Implantation is completed by

12th day after ovulation

secreted by trophoblast cells that causes the corpus luteum to continue releasing progesterone and estrogen

Human chorionic gonadotropin (hCG)

hCG secretion declines when

placenta begins to secrete its own progesterone and estrogen (end of 2nd month)

what prevents polyspermy by destroying the sperm receptors?

ZIPs

the corpus luteum is formed at the site of

ovulation

time since the first day of the last menstruation

gestational age

approximately two weeks shorter than gestational age

fertilzation age

pregnancy truly begins at

implantation

time from the last menstrual period until birth

gestation period

what cell process is happening to the zygote right after fertilzation

cell division

zygote daughter cells are called

blastomeres

solid ball of 16 or more cells

morula

At day 3 or 4, the embryo is called a

blastocyte

fluid accumulation in interal cavity & lose zona pellucida

A fluid-filled hollow sphere composed of trophoblast cells and an inner cell mass.

blastocyst

why do trophoblast cells display immunsuppresive factors?

so that implantation and development can proceed without maternal immune rejection.

the inner cell mass of a blastocyst will become

embryo and chorion, yolk-sac, and amniotic sac

adheres to a site on the endometrium with the

proper receptors and chemical signals

trophoblast

two distinct layers formed by the trophoblast

• Cytotrophoblast: inner layer of cells

• Syncytiotrophoblast: cells in the outer later

Which layer formed by the trophoblast have the contents that invade and digest the endometrium allowing the blastocyst to burrow into the endometrial lining

Syncytiotrophoblast

endometrium cells grown around

blastocyst

the ______ forms from embryonic and uterine

tissues after implantation

placenta

Finger-like projections from the growing embryo that allow for nutrient and waste exchange

chorionic villi made by the trophoblast

part of the endometrium outside of the chorionic villi

Decidua basalis

chorionic villi and decidua basalis together

Placenta

Is fully formed and functional by the end of the third month

placenta

Do uterine and embryonic blood supplies intermix?

no

a fetus with a gestational age of 25 would have the fertilization age of

23 weeks (2 weeks after last menstruation)

order of zygote formation

zygote --> morula --> blastocyst

Which fetal cells digest uterine cells?

syncytiotrophoblasts

During implantation the ICM develops into a __________ that develops into the _________.

flat embryonic disc; embryo

Trophoblast cells and some cells of the embryonic disc form the

extraembryonic membranes

extraembryonic membranes contains:

amnion, yolk sac, allantois

provides a buoyant environment that protects the embryo, contains amniotic fluid

Amnion

source of the earliest blood cells and blood vessels, later forms part of the digestive tube

Yolk sac

structural base for the umbilical cord, becomes part of the urinary bladder

Allantois

In week ___, the embryonic disc develops into three primary germ layers (gastrula)

3

3 layers of the gastrula will eventually form different tissues

Ectoderm (outer layer)

Mesoderm (middle layer)

Endoderm (inner layer)

nervous system, bones and blood vessels of the head, and skin epidermis develop from which primary germ layer?

ectoderm

epithelial linings & glands of the digestive, respiratory, and urogenital systems develop from which primary germ layer?

endoderm

mesoderm forms

muscle, bone, ligaments, heart, blood vessels, kidney, gonads, serosa, walls of digestive and respiratory organs

formation of body organs and systems

organogenesis

End of embryonic period

week 8 - All organ systems are recognizable (though not functional)

The first major event in organogenesis is ________.

neurulation

Gives rise to brain and spinal cord

Three brain vesicles that are apparent by the end iof the first month

forebrain, midbrain, hindbrain

In Development of the Nervous System by the end of the second month...

• Cerebral hemispheres cover the top of the brain

• Spontaneous brain waves can be recorded

causes of neural tube defects

improper/no fusion of tube

incomplete closure of neural tube

embryonic ecotoderm gives rise to the

skin and nervous system

which structure is encolosed by a tube of endoderm and developed into the primitive gut

yolk sac

after embryonic development is _________ development

fetal

fetal period

9 weeks to birth

by the end of embryonic development (week 8) is the cardiovascular system fully functional?

yes - heart has been pumping blood since week 4

distinguishing body feature of week 8 fetus

head nearly as large as body

when in fetal development does blood cell formation begin in the bone marrow & external genitalia visible

9-12 weeks, month 3

when in fetal development does the face become human (eyes, ears, lips) and body starts outspacing head

13-16 weeks, month 4

when does fetus take fetal position due to rapid growth (lack of space) & kicking happens

17-20 weeks, month 5

when is fetus mostly viable outside except for underdeveloped lungs

21-30 weeks, months 6&7

in the developing fetus, all body systems are present by

week 8 (end of embryonic development)

Any environmental agent that can cause deviations in prenatal development

teratogen

what factor trigger testicular development during gonadal development (week 6-7)

amount of testosterone

drugs that alter sex steroid hormone homeostasis