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Gross Anatomy/Embryology > The First Three Weeks of Development > Flashcards

The First Three Weeks of Development Flashcards

1
Q

time frame of embryo

A

week 1-8

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2
Q

time frame of fetus

A

week 8-36

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3
Q

What causes most deaths during the first year post-natal (infancy)?

A

developmental anomalies cause the most deaths during infancy

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4
Q

morphogenesis

A

activities & processes that take place during embryology

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5
Q

induction

A

tissue or cell tells another cell to do something (factor acts as intermediary)

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6
Q

coelom

A

empty space inside organism not connected with outside

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7
Q

zona pellucida

A

proteoglycan shell that keeps the egg substance together

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8
Q

corona radiata

A

accumulation of cells around outside of egg

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9
Q

Describe the formation of a zygote

A
  • fusion of pronuclei –> first time in which there is the full complement of chromosomes in human
  • happens in Fallopian tube
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10
Q

blastomere formation

A
  • zygote splits into two cells where the mass of the two cells equals the mass of the original cell (the daughter cells are half the size of the first)
  • protoplasm being reduced
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11
Q

morula formation

A
  • zona pellucida still exists
  • at 16 cell phase –> no longer dividing in sequence
  • individual cells, especially cells around edge, develop tight junctions
  • ring of cells that are no longer free to float around (morula)
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12
Q

blastocyst formation

A
  • cells on outside are pumping fluid into cavity and pushing inside cells to one end (compaction –> process developing inner cell mass)
  • all cells are identical (have same potential) except for their position
  • usually in the uterus, ready to embed into wall of uterus
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13
Q

What is a possible result of blastocyst formation in the Fallopian tube?

A
  • may try to embed in Fallopian tube leading to an ectopic pregnancy
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14
Q

hatching

A
  • zona pellucida starts to degenerate
  • free to expand
  • cells no longer cuboidal –> flatten and stretch out due to one way pumping by exterior cell group
  • inner cell mass becomes embryo and exterior cell group supports embryo (trophoblast)
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15
Q

blastocyst attachment to endometrium

A
  • blastocyst rolls around slowly on wall of uterus inducing increased concentration of glands and blood vessels
  • when end with inner cell mass gets close, trophoblast attaches to endometrium
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16
Q

syncytiotrophoblasts

A
  • produced by cytotrophoblasts just outside of attachment point to endometrium
  • cells are multinucleate (tissue is called syncytium)
  • produce enzymes that are inverse and break up ECM of maternal tissue
  • cells move into empty space (maternal tissue also building up and embracing embryoblast)
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17
Q

bilaminar embryo

A
  • mass develops into upper (epiblast/ectoderm) and lower (hydroblast/endoderm) layer
18
Q

8 day embryo

A
  • cells facing fluid-filled cavity (hypoblasts) develop into simple cuboidal epithelium
  • cells facing maternal tissue (epiblasts) become pseudostratified columnar, make an empty space that becomes the amniotic cavity
  • endometrium proliferating and completely encapsulating embryo
19
Q

What cells produce the amniotic fluid in the growing amniotic cavity?

A
  • epiblastic derivatives
20
Q

Discuss the formation of Heuser’s membrane

A
  • from hypoblasts, cells forming edge and creating lining for cavity
  • cover cytotrophoblasts
21
Q

What function to the trophoblastic lacuna play in the developing embryo?

A
  • trophoblastic lacuna are fluid filled spaces in the trophoblast
  • maternal blood vessels will invade area and eventually dump blood into the lacuna but this blood does not come into contact with the embryo yet
22
Q

What function does the coagulation plug have?

A
  • coagulation plug allows doctors to endoscopically identify where the embryo has embedded in the uterine wall
23
Q

What cells produce the fibrous acellular reticulum just outside Heuser’s membrane?

A
  • cytotrophoblasts
24
Q

What cells produce the extraembryonic mesoderm?

A
  • hydroblasts produce this subset of cells that move along Heuser’s membrane and along the cytotrophoblasts
25
Q

primary yolk sac

A

edge is continuous with edge of hypoblast (fluid of primary yolk sac touching top side of hypoblast

26
Q

Where does the chorionic cavity being to form?

A
  • forms in the extramembryonic reticulum
27
Q

What layer of cells comes down and pinches primary yolk sac?

A
  • extraembryonic mesoderm

- will cause the creation of the definitive yolk sac with the outer remnant being pushed away

28
Q

What function do the primary stem villi serve?

A
  • embryo is getting big and needs to be anchored in the endometrium
  • cytotrophoblast make villi projections that extend all the way around outside of embryo to keep it fixed in endometrium
29
Q

connecting stalk

A
  • holds embryo within the huge chorionic cavity

- becomes the umbilical cord

30
Q

gastrulation

A
  • beginning is the formation of the primitive streak
  • epiblast producing mesoderm
  • epiblastic cells leave from primitive streak, turning into mesoderm, and moving into space between ectoderm and endoderm
  • cells repopulate middle AND bottom layers –> epiblastic derivatives move into middle and push hypoblasts out to become definitive endoderm
31
Q

primitive streak

A
  • formation signals the beginning of gastrulation
  • long axis along endoderm
  • more toward tail end
  • little dimple with edge that surrounds –> lifting up causes groove
32
Q

What causes the dimples in the endoderm? What are they called?

A
  • the dimples are caused from the fusing of embryonic ectoderm and endoderm
  • head region dimple = buccopharyngeal membrane (becomes mouth, etc.)
  • tail region dimple = cloacal membrane (becomes anus, etc.)
33
Q

What does gastrulation give rise to?

A
  1. definitive endoderm

2. intraembryonic mesoderm

34
Q

What cell layers are derived from the epiblasts?

A

All three (ectoderm, mesoderm, and endoderm)

35
Q

lateral plate mesoderm

A

group of epiblasts that move laterally to the primitive streak

36
Q

paraxial mesoderm

A

group of epiblasts that move up and out from primitive streak

37
Q

notochordal process

A
  • group of epiblasts that move from dimple and move longitudinally
  • cells knock away endoderm and then they themselves leave
  • amniotic cavity and definitive yolk sac in contact for a short amount of time
38
Q

What are the neural crest cells?

A
  • ectodermal derivative
39
Q

What causes the mesoderm to reorganize at the end of the third week?

A
  • caused by the folding of the neural tube
40
Q

Describe the process by which the embryo develops primitive circulation

A
  • secondary villus –> some of embryonic mesoderm
  • tertiary anchoring villus –> creates circulation (the blood vessels that are found in the umbilical cord)
  • maternal and embryonic circulations do not cross over at this point

Gross Anatomy/Embryology (5 decks)

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