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Y2 LCRS 1 - RDA > 6. Embryology- Complications of Development > Flashcards

6. Embryology- Complications of Development Flashcards

1
Q

What is the cause of conjoined twins?

A

Incomplete inner cell mass separation

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2
Q

What causes formation of identical twins/triplets?

A

1 conceptus forms 2/3 inner cell masses to form 2/3 genetically identical individuals

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3
Q

What causes chimerism?

A

2 genetically distinct conceptuses combine to form 1 individual

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4
Q

What is mosaicism?

A

Non-disjunction event resulting in differences between cells within one individual
e.g. Heterochromia

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5
Q

Name some presentations of chimerism?

A

Blaschko’s lines (lines of normal cell division)

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6
Q

When does differentiation of eyes begin?

What is the significance?

A

Day 22 post fertilization

Mosaicism/ chromosomal event must predate

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7
Q

What is Edward’s Syndrome?

A

Trisomy 18
Most die before birth, fatal
Small size and heart defects

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8
Q

What is Patau’s Syndrome?

A

Trisomy 13
Most die before birth, 80% die within 1 year
Multi-organ defects

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9
Q

What is a common presentation of mutation of KIT receptor?

A

Piebaldism

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10
Q

What is Holt-Oram Syndrome?

A

Due to mutation in TBX5 (transcription factor)
Atrial septation defects
Range of hand abnormalities

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11
Q

What is Achondroplasia?

A

Gain of function mutation in FGFR3

Defect in conversion of cartilage to bone and lack of bone growth

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12
Q

What is the main effect of lithium on development of embryo/foetus?

A

Heart malformation

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13
Q

What is the effects of amphetamines on embryo development?

A

Cleft lip and palate, heart defects

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14
Q

What effects do physical agents like X-rays have on foetal development?

A

Microcephaly
Spina Bifida
Cleft palate
Limb defects

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15
Q

Outline limb development

A

D27/28: Forelimb bud
D29: Hindlimb bud, grow out from lateral plate mesoderm rapidly under control of special signalling regions (AER-HOX genes expressed)
D56: fully formed and patterned

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16
Q

What is the zone of polarizing activity (ZPA)?

A

Area of mesenchyme that contains signals which instruct the developing limb bud to form along the anterior/posterior axis.
Usually as posterior
High conc: bud forms at posterior
Low conc: bud forms at anterior

17
Q

What is the polarizing factor for limb development?

A

Sonic Hedgehog (shh)

18
Q

What is the pathogenesis of cleft palate?

A
  • Occurs during Carnegie stage 18 (~6 weeks)
  • Lack of fusion of palatine shelves (Involves tissue migration)
  • Persistent labial groove
19
Q

What is the pathogenesis of spina bifida?

A

Failure to complete neurulation (union of 2 halves of neural arches); which is controlled by underlying notochord (posterior neuropore)

Problem present within 4 weeks of fertilisation

20
Q

What are the types of spina bifida?

Describe them.

A 
- Occulta
May be overlied by tuft of hair
- Cystica (Meningocele)
Only meninges protrude
- Cystica (Meningomyelocele)
Both meninges and CNS elements (spinal cord, cauda equina) protrude
- Myelocele
Neural folds remain open, allowing CSF to leak onto surrounding skin
21
Q

What is the pathogenesis of Anencephaly?

A
  • Anterior neuropore closure incomplete

- Similar causes to spina bifida (e.g. folic acid)

22
Q

What are the 2 possible birth defects of Thalidomide?

A
  • AMELIA - prolonged exposure leading to widespread cell death
  • PHOCOMELIA - short exposure leading to uniform cell death and only partial loss of AER signalling
23
Q

How does thalidomide cause limb defects?

A

Affects (upper limb) rapidly developing blood vessels

Administration for morning sickness at 6-8 weeks when limb is rapidly developing

24
Q

What can the teratogen amphetamines cause?

A

Cleft lip and palate

Heart defects

25
Q

What can cocaine cause as a teratogen?

A

Growth restriction, microcephaly, behavioural abnormalities

26
Q

What can alcohol cause as a teratogen?

A

Fetal alcohol syndrome
Maxillary hypoplasia
Heart defects

27
Q

When does limb rotation take place?

A

47 days onwards

28
Q

WHY and HOW do you increase in utero surfactant production during pregnancy?

A
  • Respiratory Distress Syndrome

- 1 injection of glucocorticoids/ 2-3 days

Y2 LCRS 1 - RDA (9 decks)

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