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Embryology > Early embryonic development 1 > Flashcards

Early embryonic development 1 Flashcards

1
Q

What is the ideal site of implantation for a zygote?

A

Posterior uterine wall

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2
Q

How many weeks is the pre embryonic period?

A

Weeks 1-2

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3
Q

How many weeks is the embryonic period?

A

Weeks 3-8

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4
Q

How many weeks is the foetal period?

A

Weeks 9-38

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5
Q

Define zygote

A

A fertilised ovum/oocyte

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6
Q

Define cleavage

A

The dividing of cells into two masses known as blastomeres. First cleavage happens ~30 hours after fertilisation (resting period)

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7
Q

Define zona pellucida

A

The glycoprotein ‘shell’ to prevent polyspermy

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8
Q

Define morula

A

The result of cleavage of the fertilised oocyte, each cell is Totipotent

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9
Q

Define ovary

A

The female reproductive organ producing oocytes/eggs for fertilisation

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10
Q

Define fallopian tube

A

A tube the oocyte travels along to reach the uterus. The egg is fertilised at the ampulla of the fallopian tube.

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11
Q

Define uterus

A

Female reproductive organ where implantation of the zygote and growth of the embryo occurs

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12
Q

Define blastocyst

A

Formed from the compaction of cells that make up the morula

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13
Q

Define tropoblast

A

(Outer cell mass) will later form support structures for the embryo (placenta)

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14
Q

Define embryoblast

A

(Inner cell mass) will later become the bilaminar disk

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15
Q

Define implantation

A

The attachment of the Blastocyst to the wall of the uterus at day 6 – 7

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16
Q

Define cytotrophoblast

A

(Derivative of Trophoblast) Placental membrane around the yolk sac

17
Q

Define syncytiotrophoblast

A

(Derivative of Trophoblast) Cells that invade maternal sinusoids (irregular blood vessels) resulting in uteroplacental circulation.

18
Q

What is compaction?

A

Blastomeres which make the morula compact to form the blastocyst

19
Q

What is hatching?

A

Blastocyst hatches from the zona pellucida
Allows enlargement
Allows implantation

20
Q

What is implantation?

A

Interstitial

The uterine epithelium is breached and the conceptus implants within the uterine stroma.

21
Q

What does the embryoblast differentiate into?

A

Epiblast

Hypoblast

22
Q

What does the Trophoblast differentiate into?

A

Syncytiotrophoblast

Cytotrophoblast

23
Q

At early stages of development does the embryo or placenta have priority over development?

A

Placenta

24
Q

What are the implantation defects?

A

Ectopic pregnancy

Placenta praevia

25
Q

What is an ectopic pregnancy?

A

Implantation at site other than uterine body (most commonly fallopian tube). Can quickly become a life-threatening emergency.

26
Q

What is placenta praevia?

A

Implantation in lower uterine segment. Placenta grows across cervical opening. Requires C-section delivery

27
Q

What is the embryonic pole?

A

Rapid development of Syncytiotrophoblast

28
Q

What is the Abembryonic pole?

A

Primitive yolk sac formed by Heuser’s membrane spreading across the Blastocyst cavity. Yolk sac membrane is in contact with the cytotrophoblast layer

29
Q

What is the acellular extraembryonic reticulum converted to by cellular migration?

A

extraembryonic mesoderm

30
Q

What happens in week 2 (day 11)?

A

Primitive yolk sac membrane is pushed away from the cytotrophoblast layer by an acellular extraembryonic reticulum.

31
Q

What happens in week 2 (day 12)?

A

Maternal sinusoids invaded by syncytiotrophoblast.
Lacunae become continuous with sinusoids.
Uteroplacental circulation begins.
Uterine stroma prepares for support of the embryo.

32
Q

What happens in week 2 (day 13)?

A

Formation of secondary yolk sac
Pinches off from the primary yolk sac
A.k.a. Definitive yolk sac

33
Q

What forms the Chorionic cavity?

A

Spaces within the extraembryonic mesoderm merge

34
Q

What happens in week 2 (day 14)?

A

The Connecting Stalk suspends the embryo and its cavities in the chorionic cavity.
The connecting stalk is a column of mesoderm, and is the future umbilical cord.

35
Q

What can be confused with menstrual bleeding at the end of week 2?

A

Bleeding around now can be confused with menstrual bleeding.

36
Q

What has happened by the end of week 2?

A

The conceptus has implanted
The embryo and its two cavities (Amniotic cavity and Yolk sac) are
Suspended by a connecting stalk in a
supporting Sac (Chorionic Cavity)

Embryology (7 decks)

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