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LCRS RDA > Integration of information- embryology > Flashcards

Integration of information- embryology Flashcards

1
Q

What forms when the blastocyst implants?

A

Syncytiotrophoblast

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2
Q

What does the embryo consist of?

A

A bilaminar disc (epiblast and hypoblast)

- it’s a circular disc

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3
Q

In terms of embryonic development, what has developed by day 15/16?

A

Formulation of a trilaminar disc via gastrulation- it is now elongated in the anterior/posterior direction
Buccopharyngeal membrane begins to develop
Towards the tail of the embryo, there is a primitive streak which is a cleft between the cells in the epiblast layer

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4
Q

What is the result of gastrulation?

A

3-layered embryo which gives rise to three germ types- mesoderm, ectoderm and endoderm

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5
Q

What moves through the primitive streak?

A

Cells from the epiblast- they move through the primitive streak into a gap that’s opened up between the epiblast and hypoblast

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6
Q

What happens when cells from epiblast move through primitive streak?

A

They undergo differentiation to form mesoderm cells
There are multiple layers of cells moving, implying there’s proliferation in the epiblast before they move into the streak.

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7
Q

What does ectoderm give rise to?

A

Skin and CNS

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8
Q

What does the mesoderm give rise to?

A

Skeleton, muscle, kidney, heart and blood

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9
Q

What does the endoderm give rise to?

A

Gut, liver and lungs

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10
Q

How has the embryonic disc grown by day 21?

A

The embryo has elongated a lot and there is differentiation of the mesodermal cells between the primitive node and the buccopharyngeal membrane to form the notochord

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11
Q

What does the notochord go on to develop in simple organism and also most vertebrates?

A

In simplest organisms, the notochord is the CNS but in most other vertebrates, the notochord directs the formation of the CNS

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12
Q

When does formation of CNS begin?

A

Around day 17

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13
Q

What does the ectoderm undergo differentiation to form?

A

Neural cells

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14
Q

What does the neural plate do after it has expanded?

A

It begins to fold at around day 21- there is a cleft in the middle of the neural plate which occurs above the notochord

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15
Q

What effect does the notochord have on near cells?

A

It stops the change of cells- they stop proliferating/differentiating- To hold base of the to-be-neural tube in place

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16
Q

What is cell activity like in the neural folds?

A

There’s movement and differentiation of cells which are becoming prominent over next few days

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17
Q

When do neural folds stop expanding?

A

When they meet each other to form the tube above the notochord- this becomes the CNS

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18
Q

Around day 19, what is the mesoderm doing?

A

The mesoderm is continuing to proliferate rapidly while neural folds are developing as it will form the major components of the body (trunk, muscles, bones etc)

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19
Q

How does the amnion change?

A

The amnion initially lies mainly over the embryo but around day 19, the amnion seems to have a more rounded structure surrounding the embryo at the top
By day 21, most of the embryo is within the amniotic cavity

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20
Q

How do the changes in the amnion occur?

A

The amnion moves down and around the embryo and the embryo also moves upwards

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21
Q

What is the yolk sac connected to?

A

Digestive system as it provides nutrients

22
Q

How important is the yolk sac in humans?

A

Not vital as it’s not only source of nutrients

23
Q

What happens at day 28, in terms of amniotic cavity?

A

It completely surrounds the embryo

24
Q

What happens to the yolk sac at day 28?

A

It doesn’t get cut off but it is believed that the amnion fuses around the yolk sac

25
Q

What is found where the amnion fuses around the yolk sac?

A

It leaves a defect and this is the same place where the umbilical cord os found

26
Q

In terms of neurulation, what happens around day 22?

A

From the middle of the embryo, the neural tube begins to zip up- ~day 23, there is still an anterior and posterior neuropore but these close over next week.

27
Q

What develops at this stage near the anterior neuropore?

A

Brain development

28
Q

What can be seen in the neural tube when it has zipped up?

A

The pericardial bulge- the heart develops here

29
Q

What happens to the embryo around day 25-28?

A

It begins to curve in a head to tail direction

30
Q

What begins to develop around the base of the mesoderm at around day 25?

A

Kidney and reproductive system

31
Q

What begins to develop around the top of the mesoderm at around day 25?

A

The heart

32
Q

What stage of development is the embryo at by day 28?

A

The curve is clear cut
There’s a heart bulge, the lens of the eyes are beginning to develop, the otic placode where the ears will develop; the pharyngeal arches are developing where the vasculature begins, the limb ridges are also visible. Clearly visible tail

33
Q

Where does the angiogenic cell cluster which gives rise to vasculature begin?

A

Slightly outside the embryo

34
Q

What brings the angiogenic cell cluster into the body cavity of the embryo?

A

Folding of the head

35
Q

What does the folding of the tail bring into the body cavity?

A

The cloacal membrane which gives rise to kidneys and reproductive system- connecting stalk and yolk sac enter the body cavity at the same site

36
Q

Where are the primitive blood vessels which give rise to endocardial tubes located?

A

On the side of the embryo

37
Q

What controls development?

A

All the processes are controlled by signals from genes- complex gene interactions occur throughout development to form a foetus

38
Q

What are the Hox genes involved in?

A 
Establishing:
- A-P axis
- Differences in vertebrae
- CNS divisions
- Pattern the limbs
It is involved in patterning (how cells relate to one another)
39
Q

Why is a women’s diet important in development?

A

One of the signals that controls the activation of Hox genes is retinoic acid, a derivative of vitamin A- so without vitamin A, Hox genes may not function properly

40
Q

When do the forelimb and hindlimb buds appear?

A

Forelimb ~day27/28

Hindlimb ~day 29

41
Q

Describe hand development

A

Day 32- Flipper-like upper limb buds develop
Day 35- hand plate forms
Day 44- Digits begin to appear in the hand plate
Day 45- Upper limbs bend at the elbow and the fingers are short and webbed
Day 55- Fingers and toes are distinct and separated

42
Q

When does apoptosis occur in limb development?

A

When the webbing between the fingers disappears

43
Q

What are the two main genes that regulate limb development?

A

Fibroblast-like growth factor-8- Growth factor produced at the end of the developing limb
Sonic hedgehog- Determines the overall structure of the limb that is developing

44
Q

What effect did thalidomide have on limb development?

A

Variably affected both sets of limbs but mainly upper limbs

45
Q

Which gender were affected more by thalidomide?

A

Boys

46
Q

What effect does fgf-10 have normally?

A

It normally has an effect in developing vasculature to the developing limb to provide nutrition

47
Q

How does thalidomide have an effect on limb development?

A

The active form hinders blood vessel development- there’s a varying degree of cell death and limb development is prevented. Upper limbs are more susceptible to damage

48
Q

What does long term and short term exposure to thalidomide lead to?

A

Long exposure- widespread cell death and all signalling/cells lost
Short exposure- Uniform cell death and only partial loss of signalling

49
Q

When was thalidomide usually taken?

A

Around 8 weeks PF when morning sickness was worst- this is a vital stage of limb development

50
Q

What is thalidomide commonly used to treat nowadays?

A

Leprosy especially in developing countries

51
Q

What is achondroplasia?

A

Form of dwarfism where long bones don’t develop properly

52
Q

What causes achondroplasia?

A

Loss of function mutation in fibroblast growth factor receptor 3 which is usually involved in development and particularly elongation of bones

LCRS RDA (10 decks)

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