Embryology Flashcards

1
Q

What is the embryonic period?

A

First 8 weeks

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2
Q

How long does it take the single fertilised egg to become a new human baby?

A

Normally 9 months

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3
Q

What is the conceptus stage?

A

Fertilisation to the end of week 3

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4
Q

What is the embryo stage?

A

Week 4 to week 8

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5
Q

What is the foetus stage?

A

Week 9 to birth

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6
Q

What is gametogenesis?

A

Germ cell formation

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7
Q

What two process take place during gametogenesis?

A

Oogenesis to oocyte (egg)

Spermatogenesis to spermatoza (sperm)

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8
Q

What is fertilisation?

A

The formation of the zygote

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9
Q

What is cleavage?

A

The period of rapid cell division

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10
Q

What forms after the Morula in cleavage?

A

Blastocyst

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11
Q

What is gastrulation?

A

The formation of the germ layers

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12
Q

What are the 3 germ layers?

A

Ectoderm, mesoderm, endoderm

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13
Q

At what stage are the body axes (head end and tail end) established?

A

Gastrulation

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14
Q

What is morphogenesis?

A

Formation of the body plan (embryonic folding (tube within a tube)

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15
Q

What is organogenesis and what weeks does it occur?

A

Primordia of all organ systems (weeks 4 - 8)

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16
Q

During what period does growth and weight gain occur?

A

Foetal period

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17
Q

During what period do tissues mature and become functional?

A

Foetal period

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18
Q

What period does overt sexual differentiation occur in?

A

Foetal period

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19
Q

What period is bone laid down and connections made in the CNS?

A

Foetal period

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20
Q

Processes underlying development: What are the 6 primary processes?

A

Cell division - increase in number of cells
Apoptosis - programmed cell death
Differentiation - change in appearance; adoption of new functions
Cell attachment - physical linkages between cells creating tissues
Induction - ability of one cell type to cause another to differentiate
Cell migration - movement from one location to another

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21
Q

Processes underlying development: What are the 3 secondary processes?

A

Axis formation/polarity
Folding/rotation - entire embryo or structures within
Increases/decreases in mass/dimension

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22
Q

What are the two sub processes of the secondary process increaseing/decreasing mass and dimension?

A
  1. Expansion - hypertrophy and hyperplasia

2. Compaction - decrease in cell mass with decrease in dimension, increase in cell number with no increase in dimension.

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23
Q

What is hypertrophy?

A

Increase in dimension with no increase in cell number

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24
Q

What is hyperplasia?

A

Increase in cell number with an increase in dimension

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25
Q

What 3 factors control development?

A

Genetic
Epigenetic
Environment

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26
Q

Where is the site of fertilisation?

A

Ampulla

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27
Q

What are the 4 stages of fertilisation?

A
  1. Sperm binds in a human specific interaction with the zona pellucida glycoprotein
  2. Acrosomal enzymes released from sperm head; the sperm digests its way into egg
  3. Egg and sperm plasma membrane fuse and sperm contents enter the cell
  4. Sperm entry triggers cortical granule release in egg cortex triggering formation of fertilisation membrane, which is impenetrable to sperm
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28
Q

What does sperm penetration of the egg also trigger?

A

Completion of the second meiotic division that leads to the formation of the haploid gamete.

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29
Q

What does fusion of the male and female pronuclei restore?

A

The diploid number of chromosomes = zygote (day 0)

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30
Q

Once the zygote is formed what does it then undergo?

A

A series of mitotic divisions which subdivide the fertilised egg into many smaller daughter cells called blastomeres.

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31
Q

Up to what stage blastomeres are thought to be totipotent?

A

Up to the 8 cell stage

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32
Q

What process forms blastocysts?

A

Compaction

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33
Q

What is the outer layer of a blastocyst?

A

Zona pellucida

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34
Q

At what day will the zygote attach to the uterus wall?

A

5.5 to 6 days

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35
Q

Name the 3 layers of the uterus from external to internal?

A

Myometrium
Perimetrium
Endometrium

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36
Q

What part of the blastocyst gives rise to the embryo?

A

Inner cell mass

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37
Q

What do the remaining cells in the inner cell mass of a blastocyst form once some have given rise to the embryo?

A

The trophoblast

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38
Q

What contributes to the placenta?

A

The trophoblast

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39
Q

Where are embryonic stem cells derived from?

A

The inner cell mass of blastocyst

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40
Q

Where does the embryo hatch from?

A

The zona pellucida

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41
Q

Once hatched, where does the embryo interact directly with?

A

Endometrial lining of uterus

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42
Q

Where are the normal implantation sites?

A

Middle or upper dorsal uterine wall

43
Q

Name 6 abnormal sites for implantation

A
Ovary
Ampulla
Uterine tube
Lower part of uterus
Cervix
Periotneum
44
Q

What is another term for the outer cell mass of a embryo?

A

Trophoblast

45
Q

Where do trophoblast cells of the embryo begin to invade?

A

The uterine epithelium

46
Q

What has occured after 9 - 12 days?

A

The implanted embryo

47
Q

By 9 - 12 days what has the syncytiotrophoblast done to the implanted embryo?

A

Extended and by erosion contacts maternal blood supply

48
Q

Where is the amniotic cavity present in an implanted embryo?

A

Present above the bilayered embryonic disc and the definitive yolk sak below

49
Q

What cavity other than the amniotic cavity has developed at 9 - 12 days (implanted embryo)?

A

Chorionic cavity

50
Q

What does the chorionic cavity encircle?

A

The entire embryo

51
Q

What streak has formed at the end of Week 2?

A

Primitive streak

52
Q

At what end of the embryo is the primitive streak at?

A

Caudal

53
Q

At what end of the embryo is the buccopharyngeal membrane at?

A

Cranial

54
Q

During the formation of the germ layers, where do cells migrate through?

A

The primitive streak

55
Q

What process is the movement of epiblast cells through the primitive streak to form the three primary germ layers?

A

Gastrulation

56
Q

In gastrulation - what is the hypoblast replaced by?

A

Definitive endoderm

57
Q

During gastrulation - where is the intraembryonic mesoderm formed between?

A

The endoderm and epiblast

58
Q

During gastrulation what does the epiblast become?

A

Ectoderm

59
Q

After 16 days what germ layer has formed?

A

Mesoderm

60
Q

What is the fate of the ectoderm?

A

Epidermis of skin

Nervous system

61
Q

What is the fate of the mesoderm?

A

Becomes subdivided

62
Q

What is the fate of the endoderm?

A

Lining of the gut tube

Lining of respiratory tract

63
Q

During the development of the mesoderm, it becomes three regions either side of what structure?

A

Notochord

64
Q

What three regions does the mesoderm divide into?

A

Paraxial
Intermediate
Lateral plate (somatic mesoderm and visceral mesoderm)

65
Q

What is the fate of the paraxial mesoderm?

A

Axial skeleton, parts of dermis, voluntary muscle

66
Q

What is the fate of the intermediate mesoderm?

A

Urogenital symptoms

67
Q

What is the fate of the lateral plate mesoderm?

A

Somatic part: lining of body wall, most of dermis, parts of limbs
Visceral part: Mesothelial covering of organs, cardiovascular system

68
Q

What type of folding: converts the open coelom into a closed cavity, creating thoracic and abdominal cavities and closing fore and hind gut…mid gut is last to close?

A

Lateral folding

69
Q

What type of folding: Forms the foregut and defines the thoracic cavity; developing heart tube displaced into thoracic cavity?

A

Cranial folding

70
Q

What type of folding: Cloacal membrane and connecting stalk are displaced ventrally alongside the neck of the yolk sac, forming the hindgut, anus and umbilical cord?

A

Caudal folding

71
Q

What four developments have occured in the 3rd month of foetal development?

A

Face more human looking (position of eyes and ears)
Limbs lengthen
First degree ossification centres in long bones and skull
Sex can be determined by external genitalia

72
Q

What development occurs in months 4 and 5 of foetal development?

A

Rapid increase in length

73
Q

What occurs in the 6th month to birth stage of foetal development?

A

Rapid increase in weight

74
Q

At what stage is the critical neural development period?

A

weeks 3 - 16

75
Q

At what stage is the critical period for heart development?

A

3.5 - 9 weeks

76
Q

At what stage is the critical development period for upper limbs?

A

4 - 9 weeks

77
Q

At what stage is the critical development period for lower limbs?

A

4.5 - 9 weeks

78
Q

At what stage is the critical period of development for ears?

A

4.5 - end of 16 weeks

79
Q

At what stage is the critical development period for eyes?

A

4.75 - end of 38 weeks

80
Q

What is the critical development period for the palate?

A

6.5 - end of 9 weeks

81
Q

What is the critical development period for teeth?

A

6.5 - End of 38 weeks

82
Q

What is the critical development period for external genitalia?

A

7.5 - end of 38

83
Q

What occurs in remodelling of the heart?

A

Going from a single tube to a four chambered structure

84
Q

What 2 septa are grown during normal atrial septation?

A
Septum primum (flexible)
Septum secundum (more rigid)
85
Q

What does the communication between right and left atria occur through?

A

Foramen ovale

86
Q

When does atrial septation one occur?

A

30 days

87
Q

When does atrial septation 2 occur?

A

33 days

88
Q

When does atrial septation 3 occur?

A

37 days

89
Q

What valve is the septum primum?

A

Valve of foramen ovale

90
Q

Function of foramen ovale: before birth - describe the pressures of the right and left atrium

A

Right atrium has higher pressure

Left atrium has lower pressure

91
Q

Function of foramen ovale: describe the pressures of the right and left atrium after birth

A

Right atrium is lower pressure

Left atrium is higher pressure

92
Q

After birth, in relation to the function of the foramen ovale, what closes off the shunt?

A

The septum primum (valve of foramen ovale) closes over the foramen ovale

93
Q

Describe the growth of the muscular portion of normal ventricial septation?

A

Grows upwards from wall of expanding ventricle

94
Q

Describe the growth of the membranous portion of normal ventricular septation?

A

Growth of tissue from endocardial cushions

95
Q

What is ventricular septation closely related to?

A

Septation of the outflow tract

96
Q

Name 4 types of congenital heart defects?

A

Atrial septal defect
Vebtricular defect
Outflow tract defects e.g. transposition of the great vessels
Combination of defects

97
Q

What occurs as a result of excessive resorption of septum primum?

A

Atrial septal defects

98
Q

What occurs as a result of absent septum secundum?

A

Atrial septal defects

99
Q

What occurs when the septum primum and septum secundum fail to fuse and the mixing of blood is prevented due to pressure difference?

A

Prove patent foramen ovale

100
Q

What 3 things occur in transposition of the great vessels?

A

Aorta exits right ventricle
Pulmonary trunk exits left ventricle
Deoxygenated blood pumped around the body

101
Q

What is the patent ductus arteriosus?

A

Connection between pulmonary trunk and aorta

102
Q

What are the 4 components of tetralogy of Fallot?

A
  1. Pulmonary stenosis
  2. Right ventricular hypertrophy
  3. Ventricular septal defect
  4. Over-riding aorta
103
Q

During the 8 weeks what can be said about the organs?

A

They are all formed, but not developed