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Principles > Principles of Medical Embryology > Flashcards

Principles of Medical Embryology Flashcards

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1
Q

How long does in utero human development last?

A

9 months
(38-40 weeks)
3 Trimesters

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2
Q

What are the names for each of these time periods?
Weeks 0-3
Weeks 3-8
Weeks 9-40

A 
Weeks 0-3 Conceptus/Embryo
Weeks 3-8
Embryonic period
Weeks 9-40
Foetal period
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3
Q

What the time at which the chance of having a congenital defect increases?

A

The first trimester is the point at which the chance of having a congential defect increases.
Week 5 is critical.

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4
Q

What are the 6 phases of embryogenesis?

A
  1. Gametogenesis
  2. Fertilisation
  3. Cleavage
  4. Gastrulation
  5. Formation of a body plan
  6. Organogenesis
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5
Q

What is a gamete?

A

A cell with a compliment of 23 chromosomes (half of the typical somatic cell).

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6
Q

How many chromosomes does a haploid cell have?

A

23 chromosomes

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7
Q

What is the definition of gametogenesis?

A

The formation of gametes.

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8
Q

What processes does gametogenesis consist of that lead to genetic variation?

A

Gametogenesis consists of mitosis and meiosis which leads to genetic variation.

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9
Q

What is the process o meiosis?

A
  1. Pairing begins
  2. Pairing of chromosomes
  3. Chiasma formation
  4. Pulling apart of double-structured chromosomes
  5. Anaphase of 1st meiotic division
  6. Cells resulting from 1st meiotic division. Cells contain 23 double-structured chromosomes.
  7. Cells resulting from 2nd meiotic division. Cells contain 23 single chromosomes.
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10
Q

What is the definition of spermatogenesis?

A

It is the formation of male gametes.

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11
Q

At what age does spermatogenesis occur?

A

It occurs at puberty and continues throughout life.

Each cycle takes around 64 days.

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12
Q

What is the production rate of spermatogenesis?

A

Around 6.5 million sperm per gam of testicular tissue/day.

Decreases with age.

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13
Q

What is the outcome of spermatogenesis?

A

22+X or 22+Y

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14
Q

What is Oogenesis?

A

It is the formation of female gametes.

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15
Q

At what age does Oogenesis occur?

A

It starts in development and ends at menopause.

By week 28-30: Primary oocytes begin meiosis but arrest in prophase until puberty.

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16
Q

When is a female’s reproductive life span determined.

A

Reproductive life span is determined in foetal life.

(Females start with 1 million eggs. When they run out of eggs, a person goes into menopause.

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17
Q

How does Down Syndrome occur?

A

This occurs when there is an additional copy of chromosome 21.

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18
Q

What typically is the cause of there being an additional copy of chromosome 21 which leads to down syndrome?

A

Nondisjunction.

75% of nondisjunction cases occur during oocyte formation.

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19
Q

What is the definition of Fertilisation?

A

The union of gametes (Sperm and oocyte) and is the formation of a zygote.

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20
Q

What is a zygote?

A

It is diploid, single cell embryo, with a sex determination (46,XX or 46XY)

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21
Q

The release of what enzymes allow sperm to penetrate zona pellucida?

A

acrosomal enzymes

22
Q

Sperm penetration triggers completion of what?

A

Completion of 2nd meiotic division.

23
Q

How does sperm penetration stop other sperm cells from entering the egg?

A

Sperm penetration causes cortical granules to release their contents, rendering zona pellucida impenetrable to others.

24
Q

What is the definition of cleavage?

A

It is a period of rapid cell division.

25
Q

Up until how many cells is it called a zygote?

A

16 cells.

26
Q

From 16 cells and up what is this bundle of cells called?

A

Morula

27
Q

What is the definition of gastrulation?

A

This is the formation of the germ layers which occurs in week 3.
Body axes established

28
Q

What are the 3 layers formed during gastrulation called?

A

Ectoderm (Ecto = outer) This is the outer layer and forms e.g. the nervous system, hair, nails and skin
Mesoderm (Meso = middle)
Endoderm (Endo = inner) This forms the lining of the gut

29
Q

What is embryonic folding?

A

This is where there is a tube-within-a-tube.
Lateral folding occurs, where we are a flat disc and are rolled up.
The head has to be folded down and the tail folded up to form a foetal position.

30
Q

What is the definition of organogenesis?

A

This is the formation of organs and organ system.

31
Q

The basis of the formation of organs and organ systems are all in place by when?

A

The end of the embryonic period.

32
Q

Organs and organ systems will continue to develop during when?

A

The foetal period.

33
Q

During what trimester does the baby mainly grow in length?

A

The 2nd trimester

34
Q

During what trimester is the most weight gained?

A

3rd trimester

14g at the end of 2nd month to 3500g at birth.

35
Q

During the foetal period what are the main processes that occur?

A 
Growth and weight gain.
Tissues mature and become functional.
Overt sexual differentiation.
Bone laid down; Connections made in CNS.
(Not everything in the baby is fused together).
36
Q

The terminology and landmarks used in adults are different for those used in foetus’. what are they for both?

A 
Adults - Superior
- Posterior
- Anterior
- Inferior
Foetus - Cranial = Superior
- Dorsal = posterior
- Ventral = anterior
- Caudal = inferior
37
Q

From becoming a zygote to a human, are there a large/small number of processes?

A

Relatively small number of processes.

The processes interact with each other producing more complex outcomes.

38
Q

What are the primary cell processes that occur during development?

A 
Cell division
Differentiation
Cell attachment
Apoptosis
Induction
Cell migration
39
Q

What is the role of cell division?

A

It increases the number of cells

40
Q

What is the role of differentiation?

A

Specialisation
Change in appearance/structure
Adoption of new functions

41
Q

What is the role of cell attachment?

A

Physical/functional linkages

Formation of tissues

42
Q

What is the definition of apoptosis?

A

Programmed cell death

43
Q

What is the definition of induction?

A

It is the ability of one cell type to cause another to differentiate (directly or at a distance).

44
Q

What is the definition of cell migration?

A

Movement of cells from one location to another.

45
Q

What are the secondary processes that occur during development?

A

Axis formation/polarity

Folding/Rotation

46
Q

What is the role of axis formation/Polarity?

A

Which way is up?

Cells need to know where they are in relation to each other and the embryo as a whole.

47
Q

What is the role of folding/rotation?

A

The entire embryo or structures within it folds and rotates.
This gives the embryo its 3D form
It allows the formation of complex organ structures e.g. heart, gut
(Developing heart - starts as a simple tube. In the developing hear, cells will develop faster at the bottom of the heart to form the shape of the heart).
(We fold ourselves up into a tube and then the head is folded down and the tail is folded up).

48
Q

What controls development?

A

Genetic
Epigenetic
Enviromental

49
Q

How is development genetically controlled?

A

Gene expression - tightly regulated in time and space

50
Q

How is development epigenetically controlled?

A

Preferential expression of either the maternal or the paternal copy of a gene.
Epigenetics is a science in it’s very early stages).

51
Q

Deleted region chromosome 15 contains 2 paternally expressed genes and 1 maternally expressed gene. What is the difference if the maternal or paternal chromosome is deleted?

A

Angelman Syndrome
Deletion on maternal chromosome 15 mental retardation; poor motor development
Prader-Willi Syndrome
Deletion on paternal chromosome 15 Mental retardation; Obesity; Hypogonadism (where the external genetalia is much smaller).

Principles (57 decks)

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