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Cancer and Signalling > Life Before Birth > Flashcards

Life Before Birth Flashcards

1
Q

what is embryology?

A

the study of development of an embryo from the stage of fertilisation until the fetal stage

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2
Q

preimplantation stage

A

week 1

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3
Q

embryonic stage (organogenesis)

A

weeks 2-8 (where development of placenta happens)

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4
Q

fetal stage (growth and development)

A

weeks 9-38

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5
Q

cleavage

A

mitotic divisions of fertilised egg, overall size remains the same. It is allowed passage through the narrowest part of the uterine tube (ISTHMUS) and is surrounded by a tough glycoprotein coat (ZONA PELLUCIDA)

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6
Q

morula

A

around 4 days after fertilisation, cells maximise contact with each other, forming a cluster of cells held together by tight junctions which helps with communication and signalling between the cells. it enters the uterus

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7
Q

blastocyst formation

A

the first sign of cellular differentiation, inner cell mass goes on to form the embryo and extraembryonic tissues
outer cells trophoblasts contributes to the placenta
as the embryo enters the uterine cavity, fluid enters via the zone pellucid into the spaces of the inner cell mass. a fluid filled blastocyst cavity forms

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8
Q

what typically happens on day 7?

A

the blastocyte hatches out of the zone pollucida

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9
Q

why does the blastocyte need to hatch?

A

it begins to run out of nutrients and needs to implant

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10
Q

how does the blastocyte hatch?

A

Icm cells undergo proliferation and the fluid builds up in the cavity, eventually resulting in the blastocyte hatching from the zone pellucid to facilitate implantation

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11
Q

when does implantation occur?

A

in week 2 of development

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12
Q

what is implantation?

A

the interaction between the embryo and the endometrial layer of the uterus

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13
Q

what do inner cell mass cells form

A

the embryo

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14
Q

what do trophoblast cells form

A

the placenta

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15
Q

what is a blastocyst?

A

consists of two cell populations, inner cell mass and trophoblasts

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16
Q

when does decidualisation occur?

A

when the blastocyst makes contact with the endometrium of the uterus

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17
Q

what happens during decidualisation?

A

it is a process that results in several changes in the endometrium to prepare for pregnancy. it happens in the stromal cells of the uterus. these cells will form the maternal complex of the placenta. the process triggers the production of several molecules and promotes the trophoblast cells to become invasive.

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18
Q

what are cytotrophoblasts?

A

a single layer of cells closest to the inside of the embryo

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19
Q

what is the syncytiotrophoblast?

A

more invasive and extensive than the cytotrophoblasts. it is the outer layer of cells.

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20
Q

what is the bilaminar disc?

A

the 2 layers formed from the inner cell mass, the epiblasts and hypoblasts

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21
Q

how is the diffusion of oxygen, waste and nutrients via the blood supply established?

A

towards the end of week 2, the implanting syncytiotrophoblast cells communicate with the maternal side of the placenta and establish a connection to able this diffusion

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22
Q

what is hCG (human chorionic gonadotrophin)

A

a hormone produced by the end of week 3 by the syncytiotrophoblasts which is then secreted into the urine

23
Q

what happens during week 2 of development?

A

implantation occurs, creating a connection between the embryo and the maternal endometrium.
the inner cell mass forms two laters making up the bilaminar disc, the epiblast and the hypoblast.
the trophoblast layer differentiates to form two placental layers, the cytoptrophoblast and the invasive syncytiotrophoblast

24
Q

what is an ectopic pregnancy?

A

where implantation occurs in the wrong place

25
Q

what can cause an eptopic pregnancy ?

A

clot transit through the uterine tube, premature hatching of the blastocyte or common implication of IVF

26
Q

what are extra-embryonic membranes?

A

membranes that are derived from the blastocyte but do not contribute to the embryo

27
Q

amnion

A

continuous with the epiblast of the bilaminar disc.
lines a structure called the amniotic cavity which is filled with fluid and acts to protect the developing embryo
this is present up until birth

28
Q

chorion

A

double layered membrane formed by the trophoblast and the extra embryonic membranes
it lines a structure called the chorionic cavity which is seen in early pregnancy but disappears due to the expansion of the amniotic cavity.
it forms the fetal component of the placenta

29
Q

yolk sac

A

continuous with the hypoblast of the bilaminar disc.
it is important in nutrient transfer in weeks 2-3 but disappears completely by week 20
important in blood cell formation and formation of the gut

30
Q

allantois

A

forms as an outgrowth of the yolk sac
it contributes to the umbilical arteries and connects to the fetal bladder
in non human mammals it acts as a reservoir for fetal urine

31
Q

what is gastrulation

A

the process of cell division and migration resulting in the formation of three germ layers

32
Q

what is the primitive streak?

A

a thickened area of cells which appears at the tail end of the cells. a small bulge at the end called the primitive node

33
Q

how are the 3 layers formed?

A

the epiblast evaginates (cells move towards the primitive streak and move down under the epiblast and spread out again) and creates 3 new layers of cells. this is controlled by fibroblast growth factor 8 which is made by primitive streak

34
Q

what are the 3 layers (outside to inside)

A

ectoderm, mesoderm, endoderm

35
Q

what produces the ectoderm?

A

the top layer of epiblasts

36
Q

what are some examples of ectoderm derivatives?

A
  • epidermis of skin
  • nervous system
  • tooth enamel
  • epithelial lining of mouth and anus
  • cornea and lease of eye
37
Q

what are some examples of mesoderm?

A
  • skeletal system
  • muscular system
  • dermis of skin
    circulatory and lymphatic system
38
Q

what are some examples of endoderm?

A
  • epithelial lining of digestive track
  • liver
    epithelial lining of resp system
  • thymus
  • Thyroid glands and parathyroid glands
39
Q

totipotent cells?

A

total power, eg zygote has the ability to make all types of cells

40
Q

pluripotent cells?

A

can make very many types of cells within the body. eg inner cell mass of blastocyte as these cells can give rise to three germ layers. another example is embryonic stem cells

41
Q

multipotent cells?

A

can make multiple cell types, eg haematopoietic stem cells can differentiate into many types of stem cells

42
Q

what cells form the primitive streak?

A

epiblast cells that migrate to the midline then form the primitive streak

43
Q

what do the hypoblast cells surround?

A

the yolk sack

44
Q

what do the epiblast cells form?

A

the cavity known as the amniotic cavity

45
Q

what is the primitive streak?

A

elongates from caudal to cranial

46
Q

what happens to epiblast cells that migrate beyond the primitive streak and into the hypoblast?

A

become the endoderm

47
Q

what cells make up the ectoderm?

A

the remaining epiblast cells that do not enter the hypoblast

48
Q

what cells make up the mesoderm?

A

the majority of epiblast cells that occupy the space between the epiblast and hypoblast layers differentiate to become the mesoderm

49
Q

what is the first mesodermal tissue to form?

A

notochord

50
Q

where are somites derived from?

A

paraxial mesoderm

51
Q

what are the 3 segments of the mesoderm after it changes shape (medial to lateral)?

A

paraxial mesoderm
intermediate mesoderm
lateral plate mesoderm

52
Q

what are the different parts of the lateral plate mesoderm?

A

the one closest to ectoderm?
- somatic layer of the lateral plate mesoderm
the one closest to the endoderm - sphlanic layer of the lateral plate mesoderm

53
Q

what do the somites turn into?

A

dermatome myotome -top
sclerotome - bottom

54
Q

what does the paraxial mesoderm eventually turn into (dorsal to ventral)?

A

dermatome
myotome
sclerotome

Cancer and Signalling (8 decks)

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