week 5 Flashcards
What is the first visualized on ultrasound structure within the gestational sac
yolk sac
Fetal stage begins following the _____ period after about _____ weeks
- embryonic
2. 10
Name the layers of the embryonic disc from which all future organs and tissue is derived
- ectoderm (outer)
- mesoderm (middle)
- endoderm (inner)
early sonographic intrauterine pregnancy findings and correlated dates
- chorionic or gestational sac & yolk sac
(4 weeks gestation) - Double decidual sac (decidual basalis)
(5 weeks gestation) - heart beat
(5 weeks) - double bleb (amniotic cavity & yolk sac w/ embryo between)
( 7 weeks) - umbilical cord formed (C-shaped embryo) / balloon on a string
(6 weeks)
“ballon on a string”
yolk sac and vitelline duct /yolk stalk
critical landmark for identifying true gestational sac
yolk sac
what can the first sign of early pregnancy be seen on TV?
gestational sac @ 4/5 weeks
Mean sac diameter (MSD) at 5 weeks gestation
2-3 mm
MSD formula
l+w+h / 3
Mean Sac Diameter (MSD) equation for DAYS of pregnancy
Normal MSD (in mm) + 30
- Implantation of the blastocyst cannot happen until the _______ disintegrates
zona pellucida
Define the necessary components of a first trimester sonogram based on the “AIUM Practice Guideline for the Performance of Obstetric Ultrasound Examinations”
evaluation of uterus and adnexa to identify the presence, size, location of gestational sac(s)
___ ensures nutritional supply for early embryo before the chorion is sufficiently developed to perform this function.
secondary yolk sac
A normal GS grows ___a day from 5 to 8 weeks
1.1mm/day
T/F: decidua is included when measuring GS
FALSE; only sac fluid
if GS measure is ___ or more and you DO NOT see yolk sac it means likely failed preg
8mm
if GS measure ___ WITHOUT embryo then you worry about failed preg
16mm
MSD used to determine gestational age up to __ weeks
6
Maximum normal dimension of yolk sac
6mm
function of ____ include: Hematopoiesis
Formation of sex glands
Development of digestive tract
Transfer of nutrients
yolk sac
Yolk sac should always be seen when MSD reaches ____ TA and ___ EV
20mm TA
8mm EV
CRL at 5 weeks
2-4mm
complex of the early sonolucent amniotic sac and the secondary yolk sac with the developing embryo between them
double bleb sign
____ cells surround the trophoblast and are in direct contact with the endometrium
Cytotrophoblastic
Within the epiblast of the inner cell mass, a line of cells thickens to form a ____
primitive streak
At the beginning of week ___ the trilaminar disc folds into a “C” shaped embryo. umbilical cord forms
6
TA = 25mm MSD & EV = 16mm MSD at ___ weeks
6
When are the amniotic and chorionic (gestational sac) cavities routinely imaged with endovaginal ultrasound
week 5
By week ___ amnionic should fuse with chorionic cavity and you should NOT see it anymore
14-16
difference between mensural age and embryologic age
menstrual age = date from fertilization
embryologic age = date from LMP
This is the most critical stage of development. Any disturbance at this age will likely result in major malformations and/or malfunctions
10 weeks
embryo is now termed a “fetus” in week __
11
what is CRL and what is it used for
Crown Rump Length
- most accurate measurement in estimating EDD
- starting at 5.5 weeks
- used until 12 or 13 weeks
- highly accurate
CRL formula
CRL (in cm) + 6 = age in weeks
umbilical cord is surrounded by ___ jelly
Wharton’s
Amnion contains
- 2 arteries
- 1 vein
- wharton’s jelly
formation of umbilical cord from out to inner layers
- villous chorion
- body stalk
- chorionic cavity
- umbilical vesicle & amnionic cavity
- stem of umbilical vesicle
- umbilical cord
___ keeps growing an encircles the body stalk
amnionic cavity
_____ are identified in all embryos 5mm or larger
Cardiac pulsations
characteristics of week \_\_\_: Differentiate head from trunk Limb buds Eyes wide apart Head length = Torso length Liver takes over hCG production
8
how and when is the “midgut” formed
midgut herinates into umbilical cord bc midgut elongates faster than growing embryo
-seen sonographically as echogenic line 7-10 weeks
around week ___ the fetus has developed all rudimentary forms of organs
11
at 6 weeks, 3 primary brain vesicles develop
- prosencephalon (forebrain)
- mesencephanol (mid brain)
- rhombencephalon (hind brain)
2 parts of prosencephanol
- telencephalon (hemispheres)
- Ant brain & lateral ventricles - diencephalon (thalamus)
- post brain & 3rd ventricle
___ forms 4th ventricle, pons & cerebellum
hindbrain (rhombencephalon)
@ 9 weeks the crescent-shaped sonolucency in the anterior aspect of the brain is created by the
diencephalon & mesencephalon
spine is evident and brain contains lateral ventricles filled with echogenic choroid plexus
12 weeks
limb buds begin to appear
8th week
hands and feet can be identified @ ___ weeks
10
embryonic heart measured using ___
m-mode tracing
heart rate at 5-6 weeks
100BMP
heart rate at 6+ weeks
120-160 BMP
Implantation bleed
Appears post implantation ~21 days LMP
-Sonographically as a sonolucent space outside the gestational sac
when is TIS (thermal index for soft tissues) used
1st trimester imaging
when is TIB (thermal index for structures near bone) used
2nd / 3rd trimester imaging
example of applying ALARA is ___
using M-mode instead of 3D or colour
portion of the chorion that develops into the fetal portion of the placenta
Chorion Frondosm
part of the chorionic membrane that covers the placenta
chorion plate
contains amniotic fluid & fetus
amnionic cavity
contained by chorion (thin membrane) gets smaller as amniotic cavity enlarges
- contains yolk sac
chorionic cavity
amnionic and chorionic normally fuse at ___ weeks
16
elongated duct that contributes to the development of the umbilical cord and placenta during the first trimester
allantonic duct
consists of outer trophoblast and inner embryoblast
blastocyst
contains chorionic villi
- secretes hCG (all pregnancy tests based on this measurement)
trophoblast
