Twin Formation Flashcards

1
Q

What are the 2 kinds of twin formation?

A

**Monozygotic - **identical

**Dizygotic ** - fraternal (66%)

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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
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3
Q

What are some characteristics of monozygotic twins?

What two situations can monozygotic twins develop from?

A
  • look same
  • same sex
  1. separate amniotic sacs, separate chorions
  2. separate amniotic sacs, same chorion
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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
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5
Q

What are the types of triplets?

A
  1. identical - one zygote
  2. identical + singleton - two zygotes
  3. fraternal - 3 zygotes
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6
Q

What happens when there is a common chorion AND amnion?

A

multiple situations

  1. **vanishing twin - **aka fetal resorption, 1 dies and is resorbed
  2. **parasitic twin - **incompletely formed twin depends on fully formed for survival
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7
Q

How are conjoined twins formed?

A

fusion of embryonic discs

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