Twin Formation Flashcards
1
Q
What are the 2 kinds of twin formation?
A
**Monozygotic - **identical
**Dizygotic ** - fraternal (66%)
2
Q
What are the characteristics of dizygotic twins?
A
- look different
- can be same or diff. sex
- ALWAYS: 2 amnions + 2 chorions … 2 placenta
- MAYBE: placentas fuse
3
Q
What are some characteristics of monozygotic twins?
What two situations can monozygotic twins develop from?
A
- look same
- same sex
- separate amniotic sacs, separate chorions
- separate amniotic sacs, same chorion
4
Q
What are the different placental situations of monozygotic twins?
A
- Shared Placenta - most common, AKA twin placenta
- **Fused Placentas ** - 2 placentas fuse, less common
5
Q
What are the types of triplets?
A
- identical - one zygote
- identical + singleton - two zygotes
- fraternal - 3 zygotes
6
Q
What happens when there is a common chorion AND amnion?
A
multiple situations
- **vanishing twin - **aka fetal resorption, 1 dies and is resorbed
- **parasitic twin - **incompletely formed twin depends on fully formed for survival
7
Q
How are conjoined twins formed?
A
fusion of embryonic discs