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RED > L14: Fetal Development > Flashcards

L14: Fetal Development Flashcards

1
Q

What is clinical gestation

A

Time from a woman’s last periods first day

Or time of a woman last period day

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2
Q

What is the actual fertilisation compared to the clinical gestation

A

2 weeks before the clinical gestation

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3
Q

Describe what happens when the sperm and oocyte meet

A

Fertilisation

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4
Q

How does the zygote divide

A

By mitosis

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5
Q

What does the zygote form

A

2 cell
4 cell
8 cell
16- 32 cell

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6
Q

When is the cell classed as a morula

A

16+ cells

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7
Q

After the morula what forms

A

Blastocyst

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8
Q

When does the blastocyst implant into the endometrium

A

Implantation window

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9
Q

When does the implantation window appears

A

Mid secretory phase

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10
Q

At week 2 when the blastocyst is implanted what happens to it

A

Differentiate to form the bilaminar germ disc

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11
Q

What is the bilaminar germ disc made of

A

2 layers of
Epiblast
Hypoblast

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12
Q

What happens in week 3

A

Gastrulation

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13
Q

What is gastrulation

A

When the epiblast migrates through the primitive streak to form the ectoderm, mesoderm, endoderm (replacement of hypoblast)

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14
Q

At the end of week 3 what is formed

A

The trilaminar germ disc (ectoderm, mesoderm, endoderm) of

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15
Q

In week 4 what occurs

A

Neurlation

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16
Q

What does neuralation from

A

The neural tube

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17
Q

What happens to the flat trimlaminar disc

A

Folds to from a cylindrical embryoblast

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18
Q

What are the 2 types of folding that occur

A
  • cephalo-caudal folding

- lateral folding

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19
Q

What does the folding allow

A

Organs to the correct anatomical position

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20
Q

What is week 3 onwards known as

A

The embryonic period

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21
Q

What happens during week 3-8 (clinical gestation 5 to 10 week)

A

Organogenesis

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22
Q

What is organogenesis

A

Establishment of main organs of the fetal body

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23
Q

What is the week 9 to 38 (clincal gestation 11 to 40) known as

A

Fetal period

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24
Q

What occurs during the fetal period

A

Maturation of organs and growth rather than growing new structures

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25
Q

What can the congenital abnormalities be

A

Structural
Functional- Organ is not working
Metabolic - enzyme and cellular defects

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26
Q

What are the causes of birth defects

A

Genetic
Environment
Unknown
Multifactorial: gene and environment

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27
Q

What can the congenital abnormalities be further classified into

A

Malformation
Disruption
Deformation

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28
Q

What is malformation

A

The complete and abnormal formation of a structure

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29
Q

What is disruption

A

Structures have formed then undergo morphological alterations

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30
Q

What is deformation

A

Mechanical factors

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31
Q

What is the most common autosomal trisomy

A

Down’s syndrome

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32
Q

What are the clinical features of Down’s syndrome

A

Craniofascial apperance
Single palmar creases
Wide sandle gap between toes

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33
Q

If a Down syndrome baby’s is born what do we need to counsel parents about

A

That the baby can have:

  • hypotonia
  • congenital heart defects
  • duodenal atresia and bowel is closed
  • learning difficulty
  • early set Alzheimer’s
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34
Q

What are all mothers offered for Down syndrome

A

Screening only if they wish

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35
Q

What are the 2 ways o inheriting trisomy 21 at fertilisation

A
  • non disjunction

- robertsonian translocation

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36
Q

What way of inheriting trisomy 21 is the most common

A

Non disjunction

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37
Q

How does non disjunction occur in trisomy 21

A

Chromosome 21 from one of the parents cell fails to separate at meiosis so one gamete has 2 chromosome 21s and at fertilisation it gives rise to 3 chromosome 21s ( 1 from father and 2 from mother)

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38
Q

How does Robertsonian translocation occur

A

When chromosome 21 wrongly joins to another chromosome of 14,15,20,21

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39
Q

What does one parent have to be for robertsonian translocation to occur

A

Translocation carrier

40
Q

What is another inheritance method if trisomy 21

A

Mosaichasim

41
Q

What happens in mosaichasim

A

When some cells have normal chromosome and some have trisomy 21

42
Q

When does mosaicism occur

A

When the zygote forms during mitosis

43
Q

What is the phenotype of Down syndrome with mosaichasim

A

Milder because there are some normal cells

44
Q

What does mosaichasim occur as a result of

A

Non-disjunction i.e chromosome 21 fails to separate during mitosis

45
Q

When we screen for Down syndrome what does it tell us

A

The chance of having the condition

46
Q

What does the screening test not tell us

A

That the baby for definite has the condition

47
Q

What are the 3 screening test for Downs syndrome

A

Combined test
Quadruple test
NIPT

48
Q

What does the combined test measure

A

Ultrasound nuchal translucency

49
Q

What is NIPT

A

A blood test

50
Q

What are teratogens

A

Agents that cause birth defects

51
Q

What are the types of teratogens

A 
Drugs 
Chemical 
Infectious agents 
Radiation 
Maternal factors 
Mechanical factors
52
Q

Name examples of drugs that are teratogens

A 
Alcohol 
Cocain 
Thalidomide 
Anti psychotics 
Anti convulsants 
Warfarin
53
Q

What are the chemicals that can be teratogens

A

Organic mercury

Lead

54
Q

What are the infectious agent that can be teratogenous

A

Rubella
CMV
ZIKA

55
Q

What are the maternal factors that are teratogens

A

Pre existing diabetes (increase risk of neural tube defect)

SLE (heart block)

56
Q

What are the mechanical factors that can be teratogens

A

Large fibroids
Oligohydromnios
Amniotic bands

57
Q

Why is timing of the teratogens important

A

If:

  • prior to post fertilisation week 2: miscarriage
  • week 3 to 8: affect organs
  • week 9 to 38: affects growth and maturation
58
Q

What is neuralation

A

The formation of the neural tube

59
Q

What are the 2 phases of neuralation

A

Primary neuralation

Secondary neuralation

60
Q

What occurs in primary neuralation

A

Shaping
Middle fusion
Creates brain
Crates spinal cord

61
Q

What occurs in secondary neuralation

A

Formation of the tail bud

62
Q

What are the 3 classification of spina bifida

A

Occulta
Meningocele
Myelomeningocele

63
Q

Which classification if the mildest form

A

Occulta

64
Q

Which classification of Spina bifida is the most severe form

A

Myelomeningocele

65
Q

What happens in occulta

A

Malformed vertebrae but is hidden with skin

66
Q

What occurs in meningocele Spina bifida

A

You have a malformed vertebrae and meninges and spinal cord fluid protrudes out through the malformed vertebrae.
Does not contain neural elements

67
Q

What is myelomeningocele spina bifida

A

The spinal cord (neural elements) protrude through the malformed vertebra

68
Q

What can the myelomeningocele cause

A

Paralysis and bowel problems if its in the sacral levels

69
Q

What is the prevention of Spina bifida

A

Folic acid (pre-conception)

70
Q

What has to happen to folic acid with maternal diabetes

A

Higher doses

71
Q

Why do we give higher doses of folic acid for women with diabetes

A

Diabetes has a higher risk of Spina bifida

72
Q

Which prominences form the fascial prominence

A 
Frontonasal prominence
Maxillary prominence (X2)
Mandibular prominence (X2)
73
Q

When does these fascial prominences form

A

In week 4

74
Q

What does a cleft lip and palate form as a result of

A

Failure of fusion of maxillary process ad medial nasal clefts that from the upper lip
Failure of fusion of the palatal shelves to from the palate

75
Q

What can the clef lip and palate be

A

Unilateral lateral i.e to one side

Bilateral i.e both sides

76
Q

What is a cleft palate

A

An effect in the palate alone and not the lip so it can be hidden

77
Q

What are the 2 abdominal wall defects that can occur

A

Omphalocele

Gastroschisis

78
Q

What is a omphalacele

A

Herniation of the bowel contents/viscera attached at the base of the umbilical cord

79
Q

Why does omphalocele occur

A

Due to midgut herniation that doesn’t go back to Fetal abdomen

80
Q

What does an omphalalocele appear as

A

A transparent sac of amnion attached to the umbilical ring

81
Q

What is gastroschisis

A

The evisceration of fetal intestine through a paraumbilical wall defect

82
Q

What is gastroschisis due to

A
  • involution of right umbilical vein or right vitelline artery
  • abnormal body wall forming
83
Q

What are the main ways for detecting for congenital anomalies

A

genetic testing

Imaging via ultrasound

84
Q

What methods involve genetic testing

A
  • screening for Down’s syndrome
  • pre-implantation genetic diagnosis if mother had a previous pregnancy affected
  • invasive testing : chronic villious testing, amniocentesis
  • non invasive: maternal blood
85
Q

Which screening methods are offered by NHS for Down’s syndrome

A

Quadruple

Combined

86
Q

What does quadruple test involve

A

Blood test from mother and looking for markers of: AFP, HCG, UE3, inhibin A

87
Q

When can quadruple test be performed

A

Between 14 weeks + 2 days up to 20 weeks

88
Q

What does combined test involved

A

Maternal blood test by looking at markers of NT, PAPPA, HCG
And
Ultrasound to look at nuchal translucency

89
Q

What is the criteria for combined test be carried out

A
  • 11 weeks + 2 days up to 14 weeks +1 day

- CRL ( 45 mm- 84mm)

90
Q

What is the nuchal translucency

A

A fluid filled area at the back of the neck that is measured

91
Q

What is NIPT (non-invasive pre-natal testing)

A

Blood test that you collect which contains the maternal dna and fetal dna

92
Q

When you have collected the blood with the maternal dna and fetal dna what do you do

A

Sequence the dna and detect for trisomy

93
Q

What is amniocentesis

A

An invasive procedure of where you collect the fluid in the amniotic sac that surrounds the fetus

94
Q

What are the risk of amniocentis

A

Miscarriage

95
Q

How can we avoid birth defects pre-conception

A
  • vaccination for rubella
  • avoid teratogenic drugs
  • folic acid to reduce neural tube defects
  • vitamin D
  • decrease iodine
  • optimise disease control such as diabetes
  • reduce BMI

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