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Respiratory System > Embryology > Flashcards

Embryology Flashcards

1
Q

What is embryology?

A

Drama of life before birth

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2
Q

List the stages of development of the human?

A
  1. Pre-embryonic phase 0-3 weeks
  2. Embryonic phase 4-8 weeks
  3. Foetal phase 9-40 weeks
  4. Postnatal, childhood, adolescence…
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3
Q

What are spermatagonia and oogonia?

A

Parent cells containing 46 chromosomes

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4
Q

When do spermatogonium undergo meiosis?

A

After adolescence

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5
Q

In females, when does meiosis 1 occur? What happens subsequently?

A

Occurs prior to birth and is arrested. Each month a matured ovum is formed and released.

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6
Q

What is a characteristic of every sperm and ovum released?

A

Each are genetically unique

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7
Q

How much sperm surrounds and penetrates the ovum?

A

Several surround, one penetrates

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8
Q

What components of the sperm penetrates the egg?

A

Pro nucleus i.e. just the chromosomes enter and fuse with the pronucleus of the ovum (thus forming the first cell of the human body)

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9
Q

What is the term for the first cell of the human body and how many chromosomes are present?

A

Zygote (46 chromosomes)

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10
Q

How much sperm is formed during meiosis?

A

4

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11
Q

What is formed during meiosis 1 in oogenesis?

A

1 ovum and 3 polar bodies

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12
Q

What happens during week 1 of the pre embryonic phase?

A

Zygote is formed and divides to form a blastocyst. This moves through the uterine tube, to reach the uterine cavity?

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13
Q

What does the zygote divide to form?

A

Blastocyst

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14
Q

46 chromosomes indicates what kind of cell?

A

Diploid cell

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15
Q

Which parent does the mitochondria come from?

A

Mother

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16
Q

By which process does the zygote divide?

A

Mitosis

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17
Q

The continuous division of cells eventually results in the formation of what?

A

Morula

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18
Q

What is Leber’s hereditary optic neuropathy?

A

blindness caused due to mitochondrial DNA being abnormal

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19
Q

By definition what is a solid mass of cells?

A

Morula

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20
Q

What happens when the number and size of cells begin to increase?

A

Nutrition to the central core of cells starts becoming difficult

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21
Q

What is formed to assist the nutrition delivery as the number and size of cells increase?

A

Blastocystic cavity?

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22
Q

What is a blastocystic cavity?

A

reorientation of cells

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23
Q

What does a blastocyst consist of?

A

outer and inner cell mass

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24
Q

What does the outer lining of the cell mass called?

A

trophoblast

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25
Q

How does the endometrium grow?

A

due to hormone release

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26
Q

What processes are at the end of the fallopian tubes?

A

fimbrae

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27
Q

Where does fertilisation occur?

A

End of the fallopian tube

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28
Q

What happens to mitosis as the cell passes through the fallopian tube?

A

Mitosis speeds up

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29
Q

How does the ovum and eventually zygote move up the tube?

A

Simple cilialted epithelium which beats the zygote up the tube

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30
Q

What happens when the uterine gains infection?

A

repaired, fibrosis scar tissue forms and cilia is lost

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31
Q

How long does the first, second and 3 cell division take respectively?

A

36 hrs
24 hrs
12 hrs
(successive cell divisions take lesser time)

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32
Q

What happens by day 5 or 6?

A

the blastula has formed and has reached the uterine cavity ready to implant in it.

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33
Q

What could occur if cilia function is abnormal?

A

Ectopic pregnancy

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34
Q

What happens in week 2 of the pre-embryonic phase?

A
  • Implantation
  • Cells that later form the embryo form a bilaminar disc
  • Sacs, membranes and cord to nourish the human conceptus
    (baby) start to form
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35
Q

Where does implantation occur and what happens?

A

At ~ 7 days the blastocyst begins to burrow into the uterine wall (endometrium)

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36
Q

What plays an important role in the burrowing of the blastocyst?

A

Chorion

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37
Q

How is the chorion developed?

A

further development of the trophoblast (divided into 2 layers)

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38
Q

What is a chorion?

A

mushy plate like disc (without cell membrane)

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39
Q

What does the chorion do/what is it part of?

A
  1. Implantation process (chorionic villi)
  2. Forms part of the placenta in due course
  3. Secretes human Chorionic gonadotropin (HCG)
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40
Q

What is HCG used for?

A

To detect pregnancy

41
Q

What doe hCG do?

A

help maintain the endometrium

by circulating through maternal blood (and urine)

42
Q

when do levels of hCG increase?

A

Levels of hCG increase till around 12 weeks -18 weeks gestation

43
Q

What happens to the cells of the inner cell mass?

A

The cells of the inner cell mass form a 2-layered flat disc called the BILAMINAR DISC which are epiblast and hypoblast.
2 cavities begin to form which are the
Amniotic cavity and
Yolk sac

44
Q

What is the purpose of the Yolk Sac?

A

embryo feeds off as well as the blood vessels and transfer of nutrients through placenta

45
Q

What is the placenta formed from?

A

Chorionic villi

46
Q

What are the main functions of the placenta?

A
  1. Foetal nutrition
  2. Transport of waste and gases
  3. Immunity
47
Q

The feotal part of the placenta contains what and is what texture?

A

foetal blood vessels and is smooth

48
Q

The maternal part of the placenta contains what and is what texture?

A

Rough and has maternal blood vessels

49
Q

The blood from maternal side does not mix with blood from uterus. So how do exchanges occur?

A

Via diffusion

50
Q

In what weeks does the placenta mature?

A

18-20wks

51
Q

Fraternal twins originate from how many zygotes? What does this say about their genetic makeup? How many placanta?

A

2 - dizygotic

Different genetic makeup, 2 placantae

52
Q

Identical twins originate from how many zygotes? How many placanta?

A

One - monozygotic (zygote divides into two by mitosis)

Same genetic makeup, share placenta

53
Q

What processes occur in week 3?

A
  1. Gastrulation
  2. Neurulation
  3. Development of Somites
  4. Early development of CVS
  5. Primitive streak
54
Q

What is GASTRULATION

Discuss what happens during this process.

A

FORMATION OF 3 GERM LAYERS (specialisation of cells)
1. Epiblast cells migrate into space between epiblast and hypoblast layers
2. Primitive streak is formed
3. Cells of primitive streak invaginate and displace Hypoblast
Forms 3 germ layers:
- Ectoderm
- Mesoderm
- Endoderm

55
Q

What does it mean by trilaminar disc?

A

Ectoderm
Mesoderm
Endoderm

56
Q

What does each germ layer of the trilaminar disc give rise to?

A
  1. Ectoderm - forms skin and nervous system (including neural tube)
  2. Mesoderm - forms vertebrae, muscles, cavities etc
  3. Endoderm - gut, respiratory system e.g.lungs
57
Q

What is the notochord and how is it formed?

A
  • A solid of cells
  • First back bone.
  • Formed from primitive streak and trimlaminar disc
58
Q

what eventually happens to the notochord?

A

Most of the notochord degenerates. The remnant of the notochord persists as the nucleolus pulposus

59
Q

What is the function of the notochord?

A

Notochord sends out signals (SHH pathway) thus induces ectodermal cells in the midline to form the neural tube.

60
Q

What does the neural tube form?

A

forebrain, midbrain, hindbrain and spinal cord development

61
Q

How is the neural tube formed?

A

Notochord sends signals which thicken cells and form a neural plate.
As a result, cells thicken, forming a nueral plate.
This plate sinks to form the neural tube

62
Q

What is the function of the neural tube?

A

Induces the medoserm to thicken

63
Q

The thickened mesoderm separates into 3 parts, what are these parts called?

A
  1. Paraxial mesoderm - either side of axis
  2. Intermediate plate mesoderm
  3. Lateral plate mesoderm
64
Q

What does the lateral plate mesoderm split to form?

A

Somatic and splanchnic mesoderm

65
Q

What is the space that is formed between the somatic and splanchnic mesoderm?

A

Intraembryonic coelom

66
Q

The paraxial mesoderm further segments itself into bricks known as what?

A

Somites

67
Q

What innervates each pair of somites?

A

spinal nerves

68
Q

How many somites are there?

A

43 pairs

69
Q

What is derived from somites?

A

Dermatome
Myotomes
Sclerotome

70
Q

What do dermatomes form?

A

Dermis of the skin

71
Q

What do myotomes form?

A

skeletal muscle

72
Q

What does the sclerotome form?

A

bones including the vertebrae

73
Q

How is the embryo able to fold on it’s lateral ends?

A

due to the weight of the mesoderm

74
Q

What covers the baby upon lateral folding?

A

Amniotic sac

75
Q

What forms part of the gut upon lateral folding

A

Yolk sac (endoderm)

76
Q

What does the intermediate plate mesoderm form?

A

Urogenital system (kidneys and reproductive system)

77
Q

What does the lateral plate mesoderm form?

A

Peritoneum, pleura and body cavities

78
Q

What day does the heart start to beat

A

day 24

79
Q

During what weeks does the pharyngeal arches develop?

A

Between 4th and 8th week

80
Q

What is teratology

A

Study of when things go wrong during development

81
Q

What are teratogens

A

environmental factors that cause abnormal development.

82
Q

What causes Congenital rubella syndrome (catarax)

A

contraction of german measles when pregnant

83
Q

What caused malformed limbs?

A

maternal use of thalidomide

84
Q

What are the breakdown causes of abnormal development?

A

60 unknown aetiology
20 multifactorial
10 environmental
10 genetic

85
Q

Name some environmental factors that can cause abnormal development

A
  • Drugs e.g. prescriptions
  • Alcohol/ tobacco
  • Infectious agents e.g. Rubella
  • Others - eg: radiation
86
Q

Name some genetic factors that can cause abnormal development

A
  • Too many/too few chromosomes e.g. Down’s syndrome and Turner’s syndrome
  • Structural changes - deletions of genes, segments of chromosomes from increased maternal age for example
87
Q

What are the risks of teratogenesis during week 1-2?

A

High risk of death, low risk from teratogens

Spontaneous abortion is most likely to occur

88
Q

What period of development has greatest sensitivity to teratogens?

A

week 3-8

89
Q

Why is week 3-8 known as a danger period to the risks of teratogenesis?

A

Danger period as when things/systems begin to develop there is a high risk of major defects

Mum may still not know they are pregnant so could be taking supplements to aid themselves but harmful to the babies development.

90
Q

What weeks have a decreasing sensitivity to teratogens?

A

week 9-38

91
Q

The risk posed by a teratogen depends on what 3 factors?

A
  • Exposure during critical periods of development
  • Dosage of drug/chemical/factor
  • Genetic constitution of embryo i.e. some more susceptible than others at equivalent doses
92
Q

How would you diagnose malformations prenatally?

A

o Blood - (to check for alpha fetoprotein)
o Ultrasound scan - 12-week anomaly scan
o Invasive tests: chorionic villus sampling and amniocentesis

93
Q

How would you diagnose malformations postnatal?

A 
Looking at;
o	Hip stability
o	Testes (descent)
o	Fingers and toes
o	Hearing
94
Q

Between what weeks does the respiratory system develop?

A

4-8

95
Q

When and where do the lungs and trachea develop from?

A

4 weeks of gestation

Ventral wall of the foregut

96
Q

What is the adult relationship between the oesophagus and the trachea?

A

Trachea anterior to oesophagus

97
Q

The folding of the embryo gives rise to what?

A

Primitive gut tube formed from the embryo

98
Q

The gut tube forms from the endoderm. What are the different parts of the gut?

A

foregut
midgut
hindgut

Respiratory System (4 decks)

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