1st Trimester Flashcards
(74 cards)
When does conceptual/embryologic age begin?
With the first day of conception, after ovulation
When does gestational age begin? Is this earlier or later than conceptional age.
With the first day of the LMP. It’s about 2 weeks before the conceptual age.
At what point is a zygote created? When does it become an embryo? When is it a fetus?
A zygote is from conception to 12 days. An embryo is from implantation to the end of the 10th week. A fetus is from 10 weeks to birth.
What is a morula? What is a blastocyst?
When a zygote undergoes cellular division and becomes 16 cells it is a morula. When it becomes 32 cells it is a blastocyst.
What happens to the follicle that released the ovum?
It collapses to form the corpus luteum and secretes estrogen and progesterone.
The blastocyst enters the uterus and attaches to the wall about 4 days after fertilization. What do the parts of a blastocyst do?
The ring of trophoblastic cells secrete HCG and the inner cell mass begins to form the embryo.
Implantation is typically completed within 12 days of fertilization. What occurs during this stage?
enzymes from the trophoblasts “eat into the maternal tissue and are nourished with lacunae: blood pools from capillaries. The zygote buries itself into the wall.
What is the difference between primary and secondary yolk sacs?
The cell mass becomes the primary yolk sac. 23 days after fertilization, the primary is pinched off and becomes the secondary yolk sac, which is seen throughout the first trimester.
What is the first system to develop? When can you tell?
The cardiovascular system develops the fastest. The heartbeat is visible around 5 or 6 weeks.
About how much does HCG level change every few days in a normal intra uterine pregnancy?
For the first 7 weeks, it doubles every 3 or 4 days. At 9-10 weeks HCG plateaus and then gradually declines.
High or Low HCG can indicate what types of abnormalities?
high HCG could indicate Down Syndrome whereas Low HCG can indicate ectopic pregnancies
What are the strongest biochemical markers for down syndrome?
PAPP-A analysis at 9-11 weeks combined with HCG levels.
What is a yolk sac and what is its purpose?
The earliest intragestational sac seen around 5 weeks. It provides nutrients to the embryo before the placenta forms.
The yolk sac should be visualized when the gestational sac measures ___ mm? The embryo should be seen when it measures __mm?
The mean sac diameter should be >12mm to visualize the yolk sac and >18mm to see the embryo.
Does visualization of the yolk sac always predict viable pregnancy?
Not always but at least in 90% of cases
The number of amnion membranes is consistent with the number of ________ in twin pregnancies.
yolk sacs.
What happens at the beginning of week 5 when the bilaminar embryonic disk turns into the trilaminar disk?
organogenesis can begin.
What must be visualized when the CRL >4mm in order to declare a living embryo?
Heart motion
When does chorioamniotic fusion of membranes occur?
14-15 weeks.
Where does the spine develop from? At what week is the spine visalized as parallel echogenic lines?
It develops from the ectoderm and is visible at around 6 weeks
What are the segments called when the rhombencephalon divides in two?
The cephalic portion is the metencephalon and the caudal component is the myelencephalon
Once rhombencephalon divides, cystic rhomboid fossa forms. What week can this be imaged?
From 8 to 10 weeks
Limb buds are embryonically recognizable at what week of gestation?
6th
Which limbs develop first?
upper limbs
