Ch. 9 Normal First Trimester Flashcards
How many hours after ovulation does fertilization occur?
24-36 hours
Where does normal fertilization occur?
In the ampulla of the fallopian tube
What is the normal number of chromosomes?
46 chromosomes, 23 pairs
The embryonic stage that is the male and female reproductive cell, ie. ovum or spermatozoa
Gamete
The embryonic stage that is a single celled fertilized ovum prior to miotic division
Zygote
a dividing fertilized ovum at 2 cell and 4 cell stages, located within the ampulla of the fallopian tube
Blastomere
a mass of dividing cells (resembling a mulberry) located in the isthmus of oviduct and enters the uterus 4 days after fertilization
Morula
Organized collection of cells which implants into the endometrium 7 days after fertilization
Blastocyst
What is the function of the trophoblast or the outer layer of cells around the blastocyst
Trophoblast cells produce hCG to extend the life of the corpus luteum. The trophoblast cells will eventually form into the placenta
The corpus luteum produces ——– which assures retention of the ——
Progesterone, endometrial lining
The inner fluid-filled cavity of a blastocyst that will become the yolk sac, embryonic disc, and amnion is known as
Blastocele
At what gestation are all three germ cell layers formed
by five weeks after LMP
Germ cell layer that becomes GI and respiratory systems
Endoderm
Germ cell layer that becomes the brain, nervous system, and skin
Ectoderm
Germ cell layer that becomes the musculoskeletal and circulatory systems
Mesoderm
Between what weeks do all major internal and external structures begin to form?
6-10 weeks
The primordial heart begins beating at what gestational age
6 weeks (think of the heartbeat bill, other organ function remains normal)
The embryonic period ends at
the end of the 10th menstrual week
When does the fetal period occur
at the beginning of the 11th menstrual week
hCG is initially produced by the ——- and later in pregnancy by the ———–
trophoblastic cells, placenta
With an IUP, hCG becomes detectable in the bloodstream how many days after ovulation?
7-10 days after ovulation or 3 weeks after LMP
hCG doubles every
48 hours or 2-3 days
When does hCG naturally plateau?
around 8-9 weeks and then declines afterwards
A ways of measuring hCG levels with either a positive or negative result
qualitative (ie. Urine results, over the counter pregnancy tests)
A ways of measuring hCG levels with either a positive or negative result
qualitative (ie. Urine results, over the counter pregnancy tests)
A ways of measuring hCG levels that provides a specific level or number that is within the bloodstream
Quantitative
What is the most common method used to detect quantitative hCG
3rd IRP (International reference preparation)
Elevated levels of hCG are seen with which type of cases
incorrect dates (further than expected)
gestational trophoblastic disease
multiple gestations
Decreased levels of hCG are seen in what types of cases
incorrect dates (not as far along as expected)
ectopic pregnancy
embryonic demise
abnormal IUP
When does the blastocyst implant into the endometrium
by the end of the 3rd week
List the three distinct layers of the decidualized endometrium
Decidua basalis, decidua capsularis, decidua parietalis/decidua vera
Layer of the decidualized endo that develops where the blastocyst implants: the maternal contribution to the placenta
decidua basalis
Maternal component of the placenta
decidua basalis
fetal component of the placenta
trophoblast/chorion frondosum
What is the chorion
The chorion becomes the fetal contribution to the placenta
What is the amnion
The amnion forms the inner cell mass. The amniotic cavity expands to fill the chorionic cavity.
When should the amnion and chorion fuse
Fusion is complete by 12-16 weeks
Define a chorionic bump
Is thought to represent a resolving hematoma. It’s significance on the pregnancy outcome is uncertain as it may be associated with an increased risk of pregnancy loss
Describe the normal doppler waveform of trophoblastic tissue
high velocity, low resistance flow (bc its providing the embryo with nutrients and oxygen
By how many weeks should a gestational sac be visualized on US
> 5 weeks
Normal sono findings of a gestational sac on US
round, oval or teardrop shaped. located toward the fundus or mid-uterus, DOUBLE DECIDUAL SIGN, GROWS 1MM A DAY, yolk sac present when MSD is > than or = to 8mm on TV US
What is the MSD formula
MSD=length + height + width/ 3. MSD should be measured inner to inner.
At what gestation should the secondary yolk sac be seen with TV US
5.5 weeks LMP
At what gestation should the secondary yolk sac be seen with transabdominal US
7 weeks LMP
The secondary yolk sac should be seen on TV US when the MSD reaches
8mm
The secondary yolk sac should be seen on transabdominal US when the MSD reaches
20mm
Name the structure that attaches the secondary yolk sac to the embryo
vitelline duct
The yolk sac should be measured inner to inner and should not exceed
6 mm or <5.6mm
What is the most accurate method of dating a pregnancy sonographically
CRL measurement (measured from top of the head to the bottom of the rump, excluding the legs)
The embryo should be seen TV when the gestational sac measures
16mm
The embryo should be seen transabdominally when the gestational sac measures
25mm
The embryo grows at a rate of
1 mm per day
CRL (mm) + —— = GA (days)
42
Anechoic, cystic structure seen in the posterior portion of the embryonic/ fetal brain
Rhombencephalon
When is the rhombencephalon seen
from 8-11 weeks
Normal midgut herniation aka physiologic omphalocele occurs at around —– weeks and should return to the abdominal cavity by —- weeks
9 weeks, 12 weeks
