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BDS1 BAMS human systems > embryology > Flashcards

embryology Flashcards

1
Q

what happens during the first week of pregnancy?

A
  • ovulation
  • fertilisation
  • implantation
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2
Q

what is a fertilised ovum called?

A

a zygote

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3
Q

what are the first cell divisions pre-embryo?

A

zygote > 2 cells > 8 cells > morula

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4
Q

what is a morula?

A

a solid mass of cells 4-6 days

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5
Q

what is a blastocyte?

A

a hollow ball of cells 6-10 days
- inner cell mass
- trophoblast

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6
Q

what does the early embryo have to secure?

A

its nutrient supply

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7
Q

what is the placenta?

A
  • permeable barrier between embryo and mother, important for resources (not permeable to cells)
  • the baby’s blood is replenished from the mother’s blood however the circulations DO NOT mix
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8
Q

what is the bilaminar embryo?

A

implanted trophoblast containing an embryo
- 10-12 days
- 2 cell layers

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8
Q

what is the bilaminar embryo?

A

implanted trophoblast containing an embryo
- 10-12 days
- 2 cell layers

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9
Q

what are the two layers of the bilaminar embryo?

A
  • epiblast
  • hypoblast
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10
Q

what does the epiblast layer of the bilaminar embryo do?

A

gives rise to embryonic ectoderm, mesoderm and endoderm

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11
Q

what does the hypoblast layer of the bilaminar embryo do?

A

participates in formation of the endoderm and extraembryonic (outwith embryo) mesoderm

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12
Q

what is the difference in the formations of identical twins vs fraternal twins?

A

in identical twins the trophoblast is fertilised by one sperm before dividing, whereas in fraternal twins, the trophoblast divides into two and are each fertilised by a different sperm

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13
Q

what is gastrulation?

A

an early developmental process in which an embryo transforms from a one-dimensional layer of epithelial cells (blastula) and reorganizes into a multilayered and multidimensional structure called the gastrula

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14
Q

describe the key points which occur during gastrultion

A

During gastrulation, the embryo develops:
- An axis (to become bilaterally symmetrical)- primitive streak
- The three embrionic cell layers
The key stage is formation of a groove, the primitive streak

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15
Q

what is the primitive streak?

A

the axis that the embryo develops during gastrulation

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16
Q

describe the involvement of the primitive streak?

A

Some ectodermal cells are induced to differentiate and migrate through the primitive streak, towards the hypoblast.
These new cells are the mesoderm. A “not so clear” interaction between the newly formed mesoderm and the hypoblast will form the endoderm.

17
Q

what is the trilaminar embryo?

A

the mesodermal cells push through the primitive streak and spread out to form a third layer

18
Q

what happens during weeks 3-8 of embryonic development?

A

organogenesis- the 3 basic germ cell layers form the major organs (CNS is one of the first to be developed)

19
Q

how is the neural tube formed?

A
  • neural groove appears in the center of the plate, dividing the future right and left sides of the embryo
  • neural folds migrate toward the midline of the embryo, eventually fusing to form the neural tube beneath the overlying ectoderm
  • cells at the dorsalmost portion of the neural tube become the neural crest cells
20
Q

what are neural tube development defects?

A

spina bifida- neural groove persists

21
Q

what is the neural groove important for?

A

development of the head

22
Q

describe the steps in which the embryo takes shape

A
  • trilaminar embryo front and back fold under midline
  • embryo folds around the yolk sac and important organs eg heart, liver and lungs appear
23
Q

what 3 cell types do all body cells come from?

A

ectoderm, mesoderm, endoderm

24
Q

what cells does the ectoderm give rise to?

A

nervous system and epidermal skin cells

25
Q

what cells does the endoderm give rise to?

A

digestive system and other internal organs

26
Q

what cells does the mesoderm give rise to?

A

muscle cells and connective tissues

27
Q

what are stem cells?

A

Stem cells are unspecialised cells (‘undifferentiated’) that can develop into more specialised cells

28
Q

what are the characteristics of embryonic stem cells?

A
  • pluripotent, meaning they can divide into more stem cells or can become any type of cell in the body- allows embryonic stem cells to be used to regenerate or repair diseased tissue and organs
  • totipotent stem cells are in the inner cell mass and are present during the first few cell divisions post-fertilization and can form any of the different types of cells in the body
29
Q

what are the characteristics of adult stem cells?

A
  • multipotent- can form other cell types but have limited potency
  • generally committed cell lines eg bone marrow stem cells
30
Q

what does stem cell development involve?

A

genes and various signalling molecules

31
Q

what are the three primary embryonic layers?

A
  • ectoderm- outer covering
  • mesoderm- middle
  • endoderm- inner lining
32
Q

what tissues are associated with ectoderm?

A

Skin
Mucous membranes of mouth, anus
Brain, spinal cord
Tooth ENAMEL

33
Q

what tissues are associated with the mesoderm?

A

Most connective tissues
- Dermis, tendons, cartilage, bone
Muscle (most)
Blood vessels
Kidney and urinary system
Reproductive system
Serous membranes

34
Q

what tissues are associated with the endoderm?

A

Alimentary canal (pharynx – rectum)
Respiratory system
Parts of urogenital system

35
Q

what is the ectomesenchyme and what tissues are associated with it?

A
  • ‘fourth’ layer, very relevant to dental studies.
    gives rise to:
    most of the peripheral nervous system: sensory and autonomic nerves
    Melanocytes in skin
    Adrenal medulla
    Most of the mesenchyme in the head (muscles, connective tissues, most dental and periodontal tissues – except enamel)
    Dentine, cementum, pulp, periodontal ligament, jaw bones. (next lecture)
36
Q

what is a syndrome?

A

when theres multiple phenotypes/diseases- complex

37
Q

what period of embryonic development has the greatest sensitivity?

A

week 3-12 (first trimester)

38
Q

when do most developmental defects occur in embryonic development?

A

the first trimester (weeks 3-12)

39
Q

what is the period of functional maturity of the embryo?

A

weeks 12-39

40
Q

What cells form the yolk sac?

A

Hypoblast

BDS1 BAMS human systems (47 decks)

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