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BRS Bioregulatory Systems > Early Fetal Development > Flashcards

Early Fetal Development Flashcards

1
Q

What two ways can we measure embryo fetal development

A

Fertilization age
Gestational age

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2
Q

Fertilization age

A

Age measured from time of fertilization
Assumed to be 1 day after ovulation

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3
Q

Gestational age

A

Age calculated from start of last menstrual period
14 days longer than fertilization age

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4
Q

What are the Carnegie stages of embryo development?

A

23 stages of embryo development
Based knowledge embryo features
Allows comparison of different developmental rates between species
0-60 days in humans

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5
Q

Embryogenic stage

A

14-16 days post fertilization
Forms early embryo from fertilized oocyte
Forms pluripotent embryonic cells
Forms extraembryonic cells

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6
Q

Embryonic stage

A

16-50 days
Establish germ layers
Establishes body plan

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7
Q

Fetal stage

A

50-270 days post fertilization
Major organs present
Migration of some organ systems
Extensive growth

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8
Q

Trimesters

A

1st consists of embryogenic and embryonic
2nd and 3rd consists of fetal stage

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9
Q

Oocyte to blastocysts

A
  • Ovulated oocyte fertilized → unicellular zygote → 2, 4, 8 cell embryos (cleavage stage embryos) → Morula (16 cell embryo) → blastocyst
  • This development is happening as the oocyte and the early embryo is migrating along to fallopian tube and into the uterus where it can implant
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10
Q

Zonna pellucida

A

Protein shell of egg cell
Protects embryo
Inhibits polyspermy

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11
Q

Up until maternal to zygotes transition what is the development of the embryo dependent on

A

Maternal mRNAs and proteins
Occurs between the 4-8 cell stage
These are made pre ovulation

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12
Q

what happens at maternal to zygotic transition

A

Transcription of embryonic genes (zygomatic genome activation)
increased protein synthesis
organelle maturation
occurs at 4-8 cell stage

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13
Q

what is compaction

A

embryo forms spherical (inner) and wedge shaped (outer cell)
occurs at the 8 cell stage
outer cells become pressed against the zona pellucida causing wedge shaped compaction
outer cells connect via tight gap junctions and desmosomes to form a barrier to diffusion

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14
Q

what cell type do inner cells give rise to

A

extra embryonic cells

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15
Q

trophoectoderm

A

the outer cells of the embryo

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16
Q

what is the blastocoel

A

fluid filled cavity in the middle of the embryo
trophoblasts pump ssodium ions into the centre of the embryo so water moves in by osmosis

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17
Q

what is hatching and why is it needed

A

when blastocysts escape the zona pellucida
occurs via enzyme degredation and cellular contractions

18
Q

What does the trophectoderm separate/differentiate into

A
  • Syncytiotrophoblast, what does it do (2 things)
    • Invades the uterine endometrium, destroying local maternal cells
    • Establishes maternal blood supply to embryo by breaking down capillaries
  • Cytotrophoblast, what does it doContinue to divide to provide a source of syncytiotrophoblasts
19
Q

What does the inner cell mass separate/differentiate into

A

epiblast which forms fetal tissue
hypoblast which forms yolk sac

20
Q

what happens to the epiblast in bi laminar embryonic disc formation

A

some cells become separated by amniotic cavity
epiblast sits on top of hypoblast layer

21
Q

What do the syncytiotrophoblasts secrete at this stage? (VSAQ no abbreviations)

A

hCG
detects beta subunit of pregnancy testing
Human chorionic gonadotrophin

22
Q

gastrulation

A

the formation of 3 germ layers
1. Epiblasts of bilaminar embryonic disc form a primitive streak
2. Primitive streak elongates and forms a primitive node
3. Primitive node contains circular depression which eventually forms a primitive groove
4. Invagination occurs (cells separate from epiblast)
5. The first cells to invaginate through the primitive groove form the definitive endoderm, (the hypoblast is displaced by spreading endoderm)
6. The remaining cells of the epiblast form the ectoderm (the exterior layer)
7. The cells in the space between the endoderm and the ectoderm, form the mesoderm

23
Q

Which organs does the endoderm give rise to? GILLT

A
  • GI Tract
  • Liver, Pancreas
  • Lung
  • Thyroid
24
Q

Which organs does the ectoderm give rise to? CST

A
  • CNS & neural crest
  • Skin epithelia (epidermis)
  • Tooth enamel
25
Q

Which organs does the mesoderm give rise to? BMGB

A
  • Blood (endothelial cells, RBCs and WBCs)
  • Muscle (smooth, skeletal and cardiac)
  • Gonads, Kidneys and adrenal cortex
  • Bone, cartilage
26
Q

notochord

A

a rod-like structure formed of cartilage-like cells which form along the embryo midline under the ectoderm

27
Q

How does notochord organize neurulation

A

controls neural plate ectoderm

28
Q

which germ layer is notochord derived from

A

mesoderm cells

29
Q

neuralation

A

Trabsfornation of neural plate into neural tube
1. Signals from notochord cause invagination of neural plate ectoderm, forming neural groove
2. Forms two neural folds containing neural crest cells
3. Neural folds fuse together over neural groove, forming a hollow tube
4. Neural tube overlaid with epidermis (which is ectoderm derived)
5. Migration of the neural crest cells from folds

30
Q

For CNS development what must happen at open ends of neural tubes

A

closure at head end and tail end
head end closure occurs first at 23 days then tail end at 27 days

31
Q

which conditions can failure of neural tube development lead to

A

spina bifida- open neural tube
anencephaly-absence of skull and brain

32
Q

Neural crest cells CCTVS

A

ectoderm
cranial
cardiac
trunk
vagral and sacral
defects of neural crest migration/specification lead

33
Q

Somitogenesis

A

Forms somites-paired blocks of paraxial mesoderm with one on each side of neural tube
1 pair every 90 mins
44 pairs

34
Q

what types of embryonic tissues do somites form

A

sclerotome gives rise to vertebrae and rib cartilage
dermamyotome which makes dermatome and myotome
dermatome-rise to dermis of skin
myotome-rise to muscle of embryo

35
Q

Gut tube formation

A

ventral folding and lateral folding of embryo pinches of yolk sac to form primitive gut

36
Q

ventral vs lateral folding

A

ventral is where head and tail end curl together
lateral is where two sides of embryo roll

37
Q

3 derivative’s of primitive gut

A

foregut-esophagus, stomach, upper duodenum, liver, gallbladder, pancreas

Midgut-Lower duodenum & remainder of small intestine, ascending colon and 2/3 of transverse colon

hindgut-last third of the transverse colon, descending colon, rectum and upper anal canal

38
Q

from which germ layer is heart derived

A

mesoderm
heart detected at 6 weeks

39
Q

From which germ layer are the lungs derived?

A

endoderm
lungs arise from lung bud

40
Q

From which germ layer are the gonads derived?

A

mesoderm
not commited to tested or ovaries
presence of SRY gene on Y chromosome causes gonodal cells to become sertolli cells triggering testes development
absence of SRY triggers granulosa cell fate and ovary development which requires reinforcement by FOXL2

41
Q

From which germ layer is the epidermis derived?

A

ectoderm

42
Q

From which germ layer is the dermis derived

A

mesoderm

BRS Bioregulatory Systems (54 decks)

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