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Developmental Biology. > Human Development. > Flashcards

Human Development. Flashcards

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1
Q

How many distinct periods can human development be broken into?

A

Embryonic development and foetal development.

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2
Q

When does the period of embryonic development occur?

A

From fertilisation up to 8 weeks of development and is where all the structures and tissue form.

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3
Q

During which period of development may the mother not realise that she is pregnant?

A

Embryonic development.

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4
Q

When does the period of foetal development occur?

A

Foetal development occurs from 8 weeks until birth and is where growth occurs.

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5
Q

When is the 1st trimester of human development?

A

1-12 weeks.

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6
Q

When is the 2nd trimester of human development?

A

12-27 weeks.

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7
Q

When is the 3rd trimester of human development?

A

28-40 weeks.

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8
Q

During what period of development does organ and body part growth occur?

A

Foetal development.

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9
Q

What is the start of embryonic development?

A

Ovulation.

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10
Q

From which follicle is the egg released during ovulation?

A

The Graafian follicle.

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11
Q

Why does the Graafian follicle erupt?

A

A surge in luteinising hormone.

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12
Q

What end of the the oviduct does fertilisation occur?

A

The fibrillated end. (The distal end).

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13
Q

How kong does it take for the fertilised egg to travel down the oviduct to the uterus?

A

Around 5 days.

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14
Q

Where does implantation of the egg occur?

A

In the uterus.

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15
Q

When will the fertilised egg hatch out of the zona pellucida?

A

Around day 5/6.

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16
Q

What is the zona pellucid called in other animals?

A

The vitelline membrane.

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17
Q

How does the egg hatch on day 5/6?

A

By the secretion of proteases from the trophectodermal cells to destroy the zona pellucida.

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18
Q

If the embryo hatches in the oviduct, what occurs?

A

An ectopic pregnancy.

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19
Q

What is the egg called once it has hatched?

A

The blastocyst.

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20
Q

What will happen once the blastocyst has hatched?

A

It will rotate to align the inner cell mass to the endometrial lining of the uterus and implant.

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21
Q

What happens on day 7 of human development?

A

Thin folds of trophectodermal cells force their way between the endometrial epithelial cells.

This is done to facilitate exchange of gases between the mothers blood and foetus’s blood.

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22
Q

What happens on day 9 of human development?

A

Some of the trophectodermal cells will fuse together to make sycntia which will proliferate and invade the uterine endometrial extracellular matrix by sending projections called chorionic villi to cause vascularisation (formation of capillaries) through the umbilical cord.

The other trophectodermal form cells are called cytotrophoblastic cells which are large multi-nucleated cells that migrate to the synctia.

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23
Q

When will the embryo secrete human chorionic gonadotropin?

A

Once the blastocyst is attached to the endometrial lining of the uterus.

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24
Q

What does human chorionic gonadotropin do?

A

Maintains the corpus luteum (Uterine endometrium).

Stimulates the production of oestrogen and progesterone to prevent the next menstrual cycle.

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25
Q

What hormone causes morning sickness?

A

HCG.

Human chorionic gonadotropin.

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26
Q

What hormone is detected in pregnancy tests?

A

HCG.

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27
Q

What percentage of fertilised eggs are miscarried?

A

70%.

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28
Q

What percentage of implanted eggs are miscarried?

A

30%.

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29
Q

When do spontaneous abortions or miscarriages usually occur.

A

In the first 10 days of pregnancy.

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30
Q

What are the 6 reasons for spontaneous abortions or miscarriages?

A

Implantation of the embryo does not occur.

Insufficient amounts of HCG to stop the menstrual cycle.

Early developmental defects prevent development.

Insufficient amounts of progesterone to maintain the corpus luteum.

Abnormal implantation.

Abnormal placenta.

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31
Q

Is the placenta derived from the mother or the embryo?

A

The embryo.

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32
Q

What does the placenta do?

A

It facilitates oxygen, nutrient and waste exchange between the embryo and the mother.

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33
Q

When does the placenta start to function?

A

At around 5 weeks.

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34
Q

How does the placenta facilitate gas exchange?

A

The umbilical veins and arteries enter the capillary bed of the chronic villus, while maternal blood forms pools between the chronic villus.

Gas exchange takes place between the foetal blood and the maternal blood.

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35
Q

Why does foetal blood take oxygen from the mothers blood?

A

Because foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin and it will strip oxygen from the mothers red blood cells.

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36
Q

What happens if the foetal blood mixes with the mothers blood?

A

The mothers immune system may kill the foetal blood cells as they are non self.

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37
Q

When does gastrulation begin?

A

Week 2-3.

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38
Q

What forms at gastrulation?

A

The 3 germ layers.

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39
Q

When does neurulation begin?

A

Week 2-3.

40
Q

What does neurulation form?

A

The brain and spinal cord.

41
Q

When does somatogenesis begin?

A

Week 2-3.

42
Q

What is somatogenesis?

A

When the muscles and bones are formed.

43
Q

When are the pharyngeal arch structures formed?

A

Week 2-3.

44
Q

What are the pharyngeal arch structures?

A

These later contribute to the formation of the face, neck, nose and mouth.

45
Q

How big is the embryo at 5 weeks?

A

1 cm long.

46
Q

How has the brain developed at 5 weeks?

A

The brain has differentiated into the forebrain, midbrain and hindbrain.

47
Q

When does the heart start beating?

A

At around week 5-6.

48
Q

When is the tail formed?

A

At around week 5-6.

49
Q

What forms the tail?

A

The lengthening of the spinal cord.

50
Q

When will the tail disappear?

A

When the vertebral column and the torso catch up with the extended spinal cord.

51
Q

When do the eyes and limb buds begin to form?

A

At around week 5-6.

52
Q

When does sexual differentiation occur?

A

At around week 7-8.

53
Q

Why do males have nipples?

A

Because sexual differentiation occurs after they are formed.

54
Q

When are the limbs fully formed with fingers and toes?

A

At around week 7-8.

55
Q

When have facial features become obvious and the eyes are developed with all of their parts.

A

At around week 7-8.

56
Q

When does the amniotic sac inflate?

A

At around week 7-8.

57
Q

When does foetal blood start to circulate?

A

At around week 7-8.

58
Q

When can brain activity be detected?

A

At around week 7-8.

59
Q

What allows the embryo to float?

A

The amniotic fluid.

60
Q

Why does the embryo need to float during development?

A

So that it can develop 3-dimensionally.

It also gives room for movement of the foetus.

61
Q

What is a condition that can be caused when there is not enough fluid in the amniotic sac?

A

Club foot.

62
Q

What is amniocentesis?

A

A process where amniotic fluid is harvested and the foetal cells that are obtained from this are used to determine whether the embryo has any genetic defects.

63
Q

When will the amniotic sac rupture?

A

Just before the baby is about to be born.

64
Q

What kind of gonad does the embryo have before 8 weeks?

A

A bi potential gonad.

65
Q

What structures does a bi potential gonad have?

A

All of the structures to make female or male reproductive parts.

66
Q

What gene is responsible for sexual differentiation?

A

A gene on the Y chromosome which is called the SRY gene.

67
Q

What does the SRY gene produce to start sexual differentiation?

A

Testes determining factor.

68
Q

What does testes determining factor induce?

A

Differentiation in the medulla of the bi-potential gonad causing testes to develop.

69
Q

What hormone do the developed testes produce?

A

Anti-Mullerian duct hormone which will destroy the Mullerian duct.

They also produce testosterone.

70
Q

What does testosterone cause in the developing male?

A

The development of secondary male structures.

71
Q

If the Y chromosome is absent from a developing embryo, what occurs?

A

The gonadal primordial will develop into ovaries.

72
Q

What do the ovaries produce in the developing female?

A

Oestrogen which allows for the development of the Mullerian duct into the uterus.

73
Q

What gene determines if the baby is a male or a female?

A

The SRY gene.

74
Q

What happens in week 12 of development?

A

Although the digits are fully formed, the hands and feet are webbed.

BMP destroys the webbing.

75
Q

What are the carnegie stages?

A

Drs will use the Carnegie scale to determine how old a foetus is.

They will use ultrasound to image the foetus and take measurements, look at developmental progress and structures to determine the age.

76
Q

What are the sensitive period of embryonic development?

A

The areas of embryo development that are more likely to go wrong than others.

77
Q

What are 2 neural tube defects?

A

Spina bifida and ancephaly.

78
Q

When do neural tube defects occur?

A

At 3-6 weeks.

79
Q

What happens if no neural tube is formed?

A

An abortion will occur.

80
Q

What are some heart defects?

A

Truncas arteriosis.

Atrial septal defects.

Ventricular septal defects.

81
Q

When do heart defects occur?

A

At 3.5-6 weeks.

82
Q

Amelia and meromelia are examples of defects to what part of the body?

A

The limbs.

83
Q

What happens when a person has amelia and meromelia?

A

Either the whole limb is lacking or the entire lib is lacking.

84
Q

When do limb defects occur?

A

5-6 weeks.

85
Q

When do cleft lips occur?

A

5-6 weeks.

86
Q

When do cleft palates occur?

A

7-8 weeks.

87
Q

What are cleft lips?

A

Cleft lips occur when the face does not fuse together properly.

88
Q

How many babies are born with a cleft palate?

A

1/700.

89
Q

What is cleft palate?

A

Where the oral cavity and the nasal cavity are the same.

90
Q

Cleft palate is a birth defect that is associated with parents of what group?

A

Alcoholics.

91
Q

What is the incidence rate of cleft palate in alcoholics?

A

1/200 live births.

92
Q

What is foetal alcohol syndrome?

A

This can cause multiple different phenotypes such as a much smaller head, small eyes, underdeveloped jaw etc.

93
Q

When does foetal alcohol syndrome occur?

A

At 4-8 weeks and

94
Q

What causes foetal alcohol syndrome?

A

Excessive drinking by the mother during pregnancy.

95
Q

What occurs during weeks 9-40 of embryonic development?

A

Embryonic development is complete and the embryo is now a foetus.

Almost all of the development and organ development is complete, so this stage consists primarily of growth.

The brain will continue to develop and the lungs will develop.

Developmental Biology. (21 decks)

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