Lesson 4A (Part 2) Flashcards
What does the yolk sac help you visualize?
To confirm the true gestational sac
How do you take a measurement of the yolk sac?
Inner to inner AP measurement
How big is the yolk sac normally when you first see it?
2.3 mm
How much does the yolk sac grow each day?
0.1mm
What is the max diameter of the yolk sac?
- 6mm
- 10 weeks
What are yolk sac pathologies associated with?
Large yolk sac
What are the functions of the yolk sac? (4)
- Providing nutrients to the early embryo
- Vitelline duct (arteries and veins) connect yolk sac to embryo
- Production of albumin, alphafetoprotein (AFP) and other proteins
- Embryonic hematopoiesis
- formation of blood cells
What happens as the placenta takes over the embryonic needs?
The yolk sac will slowly lose functionality
When does the embryo develop?
6-10 weeks
What is the embryo also known as?
Fetal pole
When does the embryo appears adjacent to the yolk sac?
6 weeks
What first appears at 6 weeks?
Embryo
- focal thickening
What does it mean if the MSD is larger than 66mm without an embryo?
May be a sign of early pregnancy failure
CRL
Crown rump length
Crown rump length
The main measurement used in 1st trimester
- the most accurate estimate of gestational age
Why is the crown rump length the most accurate estimate of gestational age?
Because there is little biological variability for CRL in the first trimester
What is crown rump length?
The length of the embryo or fetus from the top of its head (crown) to bottom (rump)
What can be seen by 7-8 weeks?
Cephalad-caudad orientation
What can be seen by 8-9 weeks?
Limb buds may be seen
What can be seen by 9-10 weeks?
Movement may be visualized
What is the 1st organ to function in the embryo?
The primitive (tubular) heart
When does the primitive (tubular) heart begin to beat?
5 weeks
- 36-37 days
When can cardiac activity be seen on an embryo?
> 5mm
When must you be able to see cardiac activity for an embryo?
If the fetal pole is 7mm
