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ESA1 - Tissues Of The Body > Early Embryonic Development 1 > Flashcards

Early Embryonic Development 1 Flashcards

1
Q

Where is the ideal site for implantation?

A

Posterior uterine wall

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2
Q

Where is the oocyte fertilised by the sperm?

A

In the AMPULLA of the Fallopian tube

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3
Q

What is a zygote?

A

Fertilised oocyte

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4
Q

What is the role of the zona pellucida?

A
  • GLYCOPROTEIN SHELL

- Prevents the blastomeres from expanding

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5
Q

When does the first mitotic division of the zygote take place?

A

30hrs after fertilisation

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6
Q

Define ‘totipotent’

A

Undifferentiated cell that has the capacity to become ANY CELL TYPE

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7
Q

How is the morula formed?

A

Cleavage of the zygote within the zona pellucida into many undifferentiated cells

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8
Q

What are the products of compaction?

A
  • Inner cell mass - EMBRYOBLAST

- Outer cell mass - TROPHOBLAST

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9
Q

Why are the cells pluripotent after compaction?

A
  • Have the capacity to become MANY cell types but cannot be ANY cell type
  • Embryoblast cells go on to form the embryo
  • Trophoblast cells go on to form the supporting cavity and do not contribute to the body
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10
Q

What is the process of hatching?

A
  • Blastocyst hatches from the zona pellucida

- Blastocyst can now interact with the posterior uterine wall and implant

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11
Q

How many cells does the conceptus consist of before implantation?

A

107

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12
Q

How many cells from the conceptus become the embryo?

A

~8

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13
Q

What does the trophoblast differentiate into during week 2?

A
  • SYNCYTIOTROPHOBLAST

- CYTOTROPHOBLAST

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14
Q

When does the bilaminar disk form?

A

Week 2

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15
Q

Describe the formation of the bilaminar disk

A
  • Differentiation of the inner cell mass (embryoblast) into 2 LAYERS
  • EPIBLAST and HYPOBLAST
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16
Q

Where does the amniotic cavity lie?

A

Between the outer cell mass and the epiblast

17
Q

Describe how implantation occurs

A
  • INTERSTITIAL

- Uterine epithelium is breached and conceptus implants within the uterine storms

18
Q

Explain the role of implantation

A
  • ESTABLISHES MATERNAL BLOOD FLOW WITHIN THE PLACENTA

- Support of embryo changes from histotrophic to haemotrophic

19
Q

What is the difference between histotrophic and haemotrophic?

A
  • HISTOTROPHIC is when the embryo absorbs nutrients through the tissues by diffusion
  • HAEMOTROPHIC is when the embryo obtains nutrients from the maternal blood
20
Q

What is meant by an ECTOPIC PREGNANCY?

A
  • Implantation occurs at a site other than the uterine body
  • Can be PERITONEAL or OVARIAN (Fallopian tube)
  • LIFE-THREATENING
21
Q

Explain why an ectopic pregnancy may be life threatening for the mother

A

Implantation in an inappropriate site may cause HAEMORRHAGE

22
Q

What is meant by PLACENTA PRAEVIA?

A
  • Implantation occurs at the LOWER UTERINE SEGMENT
  • May cause haemorrhage
  • Requires a C section
23
Q

Which implantation defect may require a C section?

A

Placenta praevia

24
Q

Describe the formation of the primitive yolk sac

A
  • Formed at the ABEMBRYONIC POLE

- Yolk sac membrane is in contact with the cytotrophoblast

25
Q

Where does the Syncytiotrophoblast rapidly develop?

A

EMBRYONIC POLE of the blastocyst

26
Q

Name two conditions linked to implantation defects

A
  • Ectopic pregnancy

- Placenta praevia

27
Q

Describe the formation of the extraembryonic mesoderm

A
  • Primitive yolk sac pushes away from cytotrophoblast via ACELLULAR EXTRAEMBRYONIC RETICULUM
  • Extraembryonic reticulum is converted to the extraembryonic mesoderm by CELL MIGRATION
28
Q

Explain how UTERINEPLACENTAL CIRCULATION begins

A
  • Syncytiotrophoblast invades the maternal sinusoids
  • LACUNAE of the Syncytiotrophoblast become continuous with the sinusoids
  • Maternal capillaries empty into the syncytium
29
Q

Describe the formation of the secondary (definitive) yolk sac

A
  • Folding of the primitive yolk sac

- Pinches off from primitive yolk sac

30
Q

What is the role of the connecting stalk?

A
  • Suspends the embryo and its cavities within the chorionic cavity
  • Develops into UMBILICAL CORD
31
Q

How is the chorionic cavity formed?

A

Merging of spaces within the extraembryonic reticulum and mesoderm

32
Q

What is the role of the outer cell mass?

A

Forms the PLACENTA and supporting tissues for the embryo

33
Q

How long is the pre embryonic period?

A

First 2 weeks after fertilisation

ESA1 - Tissues Of The Body (19 decks)

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