Embryology 2 Flashcards

1
Q

What happens during week 3?

A

Formation of germ layers (gastrulation)

Formation of neural tube (neurulatrion)

Development of somites

Early development of cardiovascular system

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2
Q

What are germ layers?

A

Layers that can germinate (grow into something)

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3
Q

What is the first thing that happens during week 3?

A

Formation of the primitive streak

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4
Q

Where is the primitive streak formed?

A

In the midline of the epiblast by the dipping in of cells (invagination)

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5
Q

What is the structure of the cells of the epiblast?

A

Columnar

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6
Q

What is formed once the primitive streak is formed?

A

Axis of the embryo

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7
Q

What does the axis of the embryo allow cells to know?

A

Where they are, at the head or the feet

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8
Q

What happens during gastruation?

A

Epiblast cells migrate into the space between the epiblast and hypoblast layers

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9
Q

What do the cells that migrate from the epiblast during gastrulation do, and cause the hypoblast to do?

A

Displaces the hypblast and forms 3 layers

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10
Q

What 3 layers do migrated cells from the epiblast during gastrulation form?

A

Ectoderm

Mesoderm

Endoderm

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11
Q

What do the migrated cells from the epiblast during gastrulation form?

A

Trilaminar disk

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12
Q

What is the trilaminar disk composed of?

A

Ectoderm

Mesoderm

Endoderm

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13
Q

What is 1?

A

Ectoderm

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14
Q

What is 2?

A

Mesoderm

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15
Q

What is 3?

A

Endoderm

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16
Q

What does the ectoderm, mesoderm and endoderm originate?

A

Epiblast

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17
Q

What happens to the cells during the formation of the trilaminar disk?

A

They become specialised, so can only go on to form certain things

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18
Q

What is formed after the trilaminar disk?

A

Notochord

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19
Q

What is the notochord?

A

Solid tube of cells

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20
Q

What does the notochord induce?

A

Ectodermal cells in the midline to form a neural tube (neurulation)

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21
Q

What does the neural tube and notochord originate from?

A

Ectoderm

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22
Q

What is A?

A

Paraxial mesoderm

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23
Q

What does the neural tube induce?

A

Mesoderm to thicken

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24
Q

What happens after the mesoderm thickens?

A

Seperates into 3 parts:

Paraxial mesoderm

Intermediate plate mesoderm

Lateral plate mesoderm

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25
Q

What does the thickened mesoderm seperate into?

A

Paraxial mesoderm

Intermediate plate mesoderm

Lateral plate mesoderm

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26
Q

What is B?

A

Intermediate plate mesoderm

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27
Q

What is C?

A

Lateral plate mesoderm

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28
Q

What are the paraxial mesoderm, intermediate plate mesoderm and lateral plate mesoderm formed from?

A

Mesoderm

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29
Q

What happens after the mesoderm splits into the paraxial, intermediate and lateral plate mesoderm?

A

Lateral plate mesoderm splits to form:

Somatic mesoderm

Splanchnic mesoderm

Space between the 2 called intraembryonic coelom

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30
Q

What does the lateral plate mesoderm split into?

A

Somatic mesoderm

Splanchnic mesoderm

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31
Q

What is the space between the somatic and splanchnic mesoderms known as?

A

Intraembryonic coelom

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32
Q

What does each part of the mesoderm go on to do?

A

Form different things

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33
Q

What does the paraxial mesoderm go onto form?

A

Somites

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34
Q

What does the intermediate plate mesoderm go onto form?

A

Urogenital system (kidneys and reproductive systems)

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35
Q

What does the lateral plate mesoderm go onto form?

A

Body cavity and coverings

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36
Q

What are somites formed from?

A

Paraxial mesoderm

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37
Q

What are kidneys and reproductive system formed from?

A

Intermediate plate mesoderm

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38
Q

What are body cavitys and coverings formed from?

A

Lateral plate mesoderm

39
Q

What is a somite?

A

Each of a number of body segments containing the same internal structures

40
Q

What does each somite (paraxial mesoderm) divide into?

A

3 structures:

Dermatome

Myotome

Sclerotome

41
Q

What are dermatomes, myotomes and sclerotomes formed from?

A

Somites

42
Q

What does dermatome form?

A

Dermis of skin

43
Q

What does sclerotome form?

A

Bones

44
Q

What does myotome form?

A

Muscles

45
Q

What do dermatomes and myotomes go onto do?

A

Migrate, with the nerve supply following them

46
Q

What is the 4th to the 8th week known as?

A

Embryonic or organogenetic period

47
Q

When is the embryonic organogenetic period?

A

4th to 8th week

48
Q

What happens during the embryonic period?

A

Folding into a tube (lateral folds)

Neural tube (forebrain, midbrain, hindbrain and spinal cord development)

Heart starts to beat on day 24

Gut formation from endoderm

Urogenital system formation from intermediate mesoderm

Body cavities from lateral plate mesoderm

43 pairs of somites form in the paraxial mesoderm and differentiate further

Limb buds form

Neck development (pharyngeal arches)

49
Q

When does lateral folding start and finish?

A

Starts in 3rd week and finishes between the 4th and 8th week

50
Q

When does the heart start to beat?

A

Day 24

51
Q

What is the gut formed from?

A

Endoderm

52
Q

How many pairs of somites are there?

A

43

53
Q

Why does lateral folding of the embryo occur?

A

Weight of cell growth causes it to bend until each end comes together

54
Q

What is A?

A

Neural tube

55
Q

What is B?

A

Somite (paraxial mesoderm)

56
Q

What is C?

A

Intermediate plate mesoderm

57
Q

What is D?

A

Endoderm (gut)

58
Q

What is E?

A

Ectoderm

59
Q

What is F?

A

Somatic mesoderm

60
Q
A
61
Q

What is G?

A

Splanchnic mesoderm

62
Q

What is H?

A

Intra-embryonic coelom

63
Q

How does head and tail folding affect the amniotic cavity and yolk sac?

A

Causes the amniotic cavity to cover the entire embryo, with the yolk sac in the middle

64
Q

What does the endoderm go onto form?

A

Gut and respiratory systems

65
Q

What is A?

A

Neural tube

66
Q

What is B?

A

Somites

67
Q

What is C?

A

Gut

68
Q

What is D?

A

Yolk sac

69
Q

What is E?

A

Limb bud

70
Q

When is the embryo formed?

A

After head to tail folding

71
Q

What is teratology?

A

Study of when things go wrong during development

72
Q

What is the study of when things go wrong during development called?

A

Teratology

73
Q

What are teratogens?

A

Environmental factors that cause abnormal development

74
Q

What are examples of teratogens?

A

Congenital rebulla syndromes caused by contraction of German measles when pregnant

Malformed limbs due to maternal use of Thalidomide

75
Q

What drug causes malformed limbs?

A

Thalidomide

76
Q

What does thalidomide cause?

A

Malformed limbs

77
Q

What causes congenetial rebulla syndromes?

A

Contraction of German measles when pregnant

78
Q

What does contraction of German measles when pregnant cause?

A

Congenital rebulla syndromes

79
Q

What are the causes of abnormal development?

A

Most are unknown (60%)

Multifactorial (20%)

Genetic (10%)

Environmental (10%)

80
Q

What are examples of environmental teratogens?

A

Drugs

Alcohol

Tobacco

Infectious agent (can transfer through placenta and affect the developing embryo)

Radiation

81
Q

What are some examples of infectious agents that can be teratogens?

A

Toxoplasma

Rebella

Cytomegalovirus

Herpes

82
Q

What are some genetic factors that may impact development?

A

Too many/few chromosomes

Structural changes (deletion of genes or segments of chromosomes)

83
Q

What can cause genetic factors that impact development?

A

Maternal age

Damage from environmental factors such as radiation

84
Q

When is embryogenesis from?

A

Weeks 3 to 8

85
Q

When is fetogenesis?

A

Weeks 9 to 38

86
Q

When is the greatest sensitivity to teratogenesis?

A

Embryonic period (weeks 3 to 8)

87
Q

What is the main risk during weeks 1 and 2?

A

High risk of death

88
Q

What does the rick posed by a teratogen depend on?

A

Exposure during critical periods of development

Dosage of drug/chemical/factor

Genetic constitution of embryo, such as some more susceptible than others at equilvalent doses

89
Q

When is the foetal period from?

A

Week 9 to 38

90
Q

What do teratogens generally cause during the embryonic and foetal periods?

A

During embryonic period causes major congenital anomalies

During foetal period causes functional and minor anomalies

91
Q

How are malformations diagnosed prenatal?

A

Blood (AFP, alpha-feto protein)

Ultrasound scan (12 week anomoly scan)

Invasive tests (chorionic villus sampling and amniocentesis)

92
Q

What is an example of an ultrasound scan?

A

12 week anomaly scan

93
Q

What are examples of invasive tests?

A

Chorionic villus sampling

Amniocentesis

94
Q

How are malformations diagnosed postnatal?

A

Hip stability

Testes

Fingers and toes

Hearing