C5.0: 1st Trimester Normal Flashcards
When is the conceptus called an embryo vs fetus?
Embryo: from conception to week 10 LMP
Fetus: After week 10
By which time are all structures formed and only need to develop?
After week 10
Reasons to do an US in the 1st trim.?
Confirm preg. Confirm location of preg Confirm that the size of the embryo matches with the LMP dating Confirm # of preg. Confirm viability of preg
what is the only way to confirm the viability of the preg?
Demonstrate the fetal heart beat with M mode (not doppler)
How do we confirm that the size of the embryo agree with the dating of LMP?
CRL measurement
A preg under how many weeks should have an EV?
Under 7 weeks
how long does the ovum live for?
12-24 hours
What is a normal sperm count and what is considered sterile? Approx. how long do sperm live?
100 million per ml is normal
20 million or less per ml is sterile
Live for approx. 24 hrs and up to 72 hrs
By what process are sperm and eggs produces?
Meiosis
How many sperm are produced by meiosis, and how many eggs?
4 sperm
1 egg
When does the 2nd meiotic division of the ovum occur?
After fertilization
How many autosomes are contributed by each parent?
And how many sex chromosome?
22 auto from each
1 sex chromo from each
Which sex chromosome does the mom always give?
X
when specifically does the Corona Radiata nourish the egg?
Before implantation
What happens to the sperm during fertilization?
It penetrates the zone pellucida and it drops its tail and the head enlarges to become the male pronucleus
What happens to the egg immediately after fertilization?
It undergoes its second meiotic division to become the female pronucleus
What occurs after the 2 pronuclei are formed?
They fuse and the chromosomes mix
What is a zygote? And whats another term for it?
The union of sperm and egg
Also called conceptus
What is a Morula?
A cluster of cells that undergo cell division but the morula doesnt get any larger…. the cells just become smaller with each division
When does a morula become a blastocyst? and when does the blastocyst enter the uterus?
When fluid penetrates the zone pellucida and enters the morula forming a fluid filled cavity
5-7 days after fertilization
When is implantation complete?
~day 11-12 post ovulation
~day 9-10 post fertilization
Where does the blastocyst usually implant?
On the posterior fundal wall
What is cleavage?
Rapid cell division without a change in size of the zygote
After the first cleavage division, what are the two daughter cells called?
Blastomeres
At what number of cells is the zygote called a morula?
12-16 blastomeres
What are the 2 types of cells in the blastocyst?
1) Trophoblast (outer layer)
2) Embryoblast (inner layer)
What does the trophoblast form and what is its function?
Placenta and chorion
Function is to gain access to maternal circulation
What does the embryoblast form?
The embryo, yolk sac and amnion
What must happen to the zone pellucida before implantation?
It must disappear
The trophoblast separates into which 2 layers?
1) Syncytiotrophoblast
2) Cytotrophoblast
Function of the Syncytiotrophoblast
Produces hCG
Erodes the endometrial stroma so the blastocyst can sink in and forms lacunae in the stroma
What do the lacunae eventually become?
The intervillous spaces of the placenta
What does the cytotrophoblast produce?
Primary chorionic villi which project into the lacunae
what are the 2 types of primary chorionic villi?
Chorion Frondosum
Smooth chorion/Chorion Laeve
Chorion Frondosum
the villi directly at the implantation site… form the early placenta
Smooth chorion/Chorion Laeve
all remaining villi around the gestational sac
Which two samples can be analyzed for chromosomal abnormalities?
Amniotic fluid
Chorionic villi
What is the decidua reaction?
When the decidua cells of the endometrium increase in size to prepare for implantation (caused by hCG and progesterone)
What causes a pseudo-sac to form in the uterus?
An ectopic pregnancy because it triggers the same decidua reaction of the endometrium as an intrauterine preg.
With a pregnancy in a bicornuate uterus, what happens to the non pregnancy horn?
The decidua reaction will occur in the non preg horn (pseudo-sac formed) and it will make it look like a twin preg