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any drug, virus or infections or other exposures that can cause embryonic/fetal development abnormality
when is a human most susceptible to teratogens?
during organogenesis, the 1st 8 weeks of gestation
women's menstrual cycle:ovarian cycle-follicular phase
1st day of menstruation and lasts 12-14 days, during this phase the graafian follicle is maturing under the influence of two pituitary hormone: luteinizing hormone (LH) and follicle-stimulating hormone (FSH), the mature graafian follicle produces estrogen
womens menstrual cycle: ovarian cycle-ovulatory phase
begins when estrogen levels peak and ends with the release of the oocyte (egg) from the mature graafian follicle-referred to as ovulation
women's menstrual cycle: luteal phase
- begins after ovulation and lasts approximately 14 days
- -during this phase the cells of the empty follicle undergoes changes and form into the corpus luteum.
- pertains to the changes in the endometrium of the uterus in responses to the hormonal changes that occur during the ovarian cycle-consists of 3 phases
- -proliferative phase: following mestruation and ends with ovulation, during this phase the endometrium is preparing for implantation by becoming thicker and more vascular-due to the increasing levels of estrogen produced by the graafian follicle.
- -secretory phase: begins after ovulation and ends with onset of mestruation. during this phase the endometrium continues to thicken, primary hormone is progesterone secreted from the corpus luteum.
- -menstrual phase: occurs in response to hormonal changes and results in the sloughing off of the endometrial tissue.
(fertilization) occurs when the sperm nucleus enters the oocyte.
fertilized egg-containing 46 chromosomes (diploid)
single cell zygote undergoes mitotic cell division
mitotic cell division/mitosis
when a cell (parent cell) divides and forms 2 daughter cells that contain the same number of chromosomes as the parent cell
3 days after fertilization-16 cell solid sphere
composed of an inner cell mass known as a embryoblast
develops into the embryo and an outer cell mass known as the trophoblast
assists in implantation and becomes part of the placenta
more than one developing embryo such as twins and triplets
embedding of the blastocyte into the endometrium of the uterus-begins around day 5 or 6
what stimulates the endometrium
where does implantation occur?
upper part, posterior wall of the uterus
developing human from time of implantation to 8 weeks
formation and development of body organs-during the critical time of human development
ectoderm (outer layer), mesoderm (middle layer), and endoderm (inner layer)-form the different organs, tissues and body structure of the developing human
when is the heart formed?
3rd gestational week to the 4th week-beats at 4 weeks
week 9-birth (when organ systems are growing and maturing)
develops within the first few weeks of gestation
connects the umbilical vein to the inferior vena cava-allows the majority of the high levels of oxygenated blood to enter the right atrium
opening btwn the right and left atria-blood high in o2 is shunted to the left atrium via the foramen ovale-may take up to 3 months after birth for this to close
connects the pulmonary artery with the descending aorta-the majority of the o2 blood goes to the aorta via the ductus arteriosus and the other little bit of blood goes to the lungs
projections from the chorion that embed into the dicidua basalis and later form the fetal blood vessels of the placenta
3 layers of the endometrium
- -decidua basalis
- -decidua capsularis
- -decidua vera
the portion directly beneath the blastocyte, forms the maternal portion of the placenta
compartments or lobes of the maternal side of the placenta
functions of the placenta
metabolic and gas exchange, hormone production (progesterone, estrogen, human chorionic gonadotropin, human placental lactogen)
hormones: progesterone, estrogen, hCG, hPL
- -progesterone: facilitates implantation and decreases uterine contractility
- -estrogen: stimulates the enlargement of the breasts and uterus
- -hCG: stimulates corpus luteum so it will continue to secrete estrogen and progesterone, this hormone is detected in preg. tests (rapid increase in 1st trimester then rapid decline)
- -hPL: promotion of fetal growth by regulating glucose available to the developing human, stimulates breast development in preparation for lactation
when does the placenta become fully functional?
btwn 8th and 10th week
2 embryonic membranes
amnion and chorion
chorionic membrane (outer membrane)
develops from trophoblast
amniotic membrane (inner membrane)
develops from the embryoblast
function of amniotic fluid
cushion, prevents adherence, allows freedom of movement, consistent thermal environment
- excess amount of amniotic fluid which increases neural tube disorders, gastrointestinal, cardiac, and chromosomal disorders
- -1,500-2,000 ml
- -decreased amount of amniotic fluid
- - >500 ml
- -because of decrease in placental function
- -newborns will experience congenital renal problems
umbilical cord arteries and vein
- 2 arteries-carries deoxygenated blood
- 1 vein- carries oxygenated blood
collagenous substance, protects the vessels of the cord from compression