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Embryology > Early Development (2nd lecture) > Flashcards

Early Development (2nd lecture) Flashcards

1
Q

What is the first step of ovulation?

A

Oocyte starts the process of the first meoitic division when it is fully matured

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2
Q

What is the second step of ovulation?

A

The oocyte forms within a surrounding layer of cells and the zona pellucida covers the oocyte

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3
Q

What is the third step of ovulation?

A

The follicle develops a large cavity after developing

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4
Q

What is the 4th step of ovulation?

A

Cavity expands as zona pellucida pushes oocyte to one side

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5
Q

What is the 5th step of ovulation?

A

The oocyte is released from the corpus luteum and is in the metaphase of meiosis II

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6
Q

What is the final step of ovulation?

A

Meiosis II resumes and the corpus luteum releases hormones

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7
Q

Where do the early stages of sperm maturation occur?

A

Testes

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8
Q

What is capacitation?

A

The final stage of sperm maturation that enables the sperm to fertilise the egg

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9
Q

What part of the sperm is packed with proteins?

A

Acrosome

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10
Q

Describe phase 1 of fertilisation

A

Spermatozoa pass through the corona radiata by fusing together and breaking the coat surrounding the oocyte

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11
Q

Describe phase 2 of fertilisation

A

One (or more) spermatozoa penetrate the zona pellucida

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12
Q

Describe phase 3 of fertilisation

A

One spermatozoa penetrates the oocyte membrane and the fusion of the two membranes triggers the oocyte to undergo the 2nd meiotic division

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13
Q

Where does embryo development (week 1) occur?

A

Uterus

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14
Q

What occurs over the first 5 days of fertilisation?

A

New embryo travels from the uterine tube down into the uterine cavity

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15
Q

Where does implantation occur?

A

Uterine cavity

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16
Q

How does the penetration of the corona radiata occur?

A

Multiple sperm attempting to reach the oocyte by penetrating the corona radiata that breaks it down

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17
Q

What kind of sperm can pass freely through the corona radiata?

A

Capacitated sperm

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18
Q

What triggers the 2nd mitotic division of the oocyte?

A

Fusion of the oocyte and sperms membranes

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19
Q

Describe week one of fertilisation

A

Once the oocyte has fused with the sperm (12-24 hours), the new embryo travels from uterine tube into uterine cavity, where implantation occurs.
Cell division occurs as embryo moves

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20
Q

What is the polar axis?

A

Where the sperm has fused with the oocyte

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21
Q

Describe blastocyst hatching

A

The zona pellucid protects the blastocyst and restricts it from growing.
The blastocyst wants to interact with maternal structures so the protein breaks down to allow the blastocyst to leave. (Implantation can now occur)

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22
Q

Where is the most common implantation site?

A

Dorsal wall of uterus

23
Q

Give examples of abnormal implantation sites

A

close to cervix, uterine tube, ovary or minestras of gut

24
Q

What will occur if the embryo abnormally implants?

A

Ectopic pregnancy (these abnormal areas need blood supplies but as they are small structures, blood vessels rupture)

25
Q

What will the trophoblast do once in contact with maternal tissue?

A

Differentiate, divide and project into uterine wall

26
Q

The cells that push into the uterine form a what?

A

Syncytium

27
Q

What does a syncytium give rise to?

A

Syncytiotrophoblast

28
Q

What does the syncytiotrophoblast do to the blastocyst?

A

Pulls it into uterine wall with it and forms finger-like projections

29
Q

What occurs with the epiblast in day 8?

A

Cell division of epiblast creates a fluid that pushes the epiblast away

30
Q

What happens to the hypoblast in day 9?

A

It begins to divide at the edges and migrate to form the Heuser’s Membrane/Yolk sac

31
Q

Implantation is not visible during day 9, but what is?

A

Coagulation plug

32
Q

What is the trophoblastic lacuna?

A

Spaces within the trophoblast that fill with maternal blood

33
Q

During days 10-12, what new layer is formed?

A

Extraembryonic mesoderm (derived from both epiblast and hypoblast)

34
Q

What does the mesoderm layer separate (days 10-12)

A

The amnion from the amnionotic cavity

35
Q

In days 12-13, what sort of cavity begins to form in the extraembryonic mesoderm?

A

Chorionic cavity

36
Q

What does the cell division of the hypoblast result in (day 12-13)?

A

Cells that push away orginial yolk sac (which degenerates) and creates a definitive/secondary yolk sac

37
Q

During days 14-15, a wedge forms, what is this called?

A

Connecting stalk

38
Q

What does the wedge do?

A

Connects embryo to everything and allows formation of umbilical cord

39
Q

What is the placenta derived from?

A

Trophoblast; primary villi

40
Q

What cells are surrounded by maternal blood?

A

Cytotrophoblast (core) and syncytiotrophoblast (outer)

41
Q

What occurs in the core of the mesoder, regarding the placenta?

A

Differentiation of blood vessels

42
Q

What extends into the villus in the development of the placenta?

A

Blood vessels (from extraembryonic mesoderm)

43
Q

How does a smaller/thinner membrane between foetal blood and maternal blood occur?

A

The cytotrophoblast membrane breaks down

44
Q

Name the 1st villus

A

Syncytiotrophoblast and cytotrophoblast

45
Q

Name the 2nd villus

A

Syncytiotrophoblast; cytotrophoblast; mesoderm

46
Q

Name the 3rd villus

A

Syncytiotrophoblast; cytotrophoblast; mesoderm; villous capillaries

47
Q

Describe end of week 3

A

Blood vessles of umbilical cord are created which branch up into the core of the villi; the cytotrophoblast grows past the syncytiotrophoblast creating an outer shell for the placenta

48
Q

During the breakdown of the cytotrophoblast to create a thinner barrier between blood, what ends up being the barrier?

A

Syncytiotrophoblast

49
Q

In the 2nd half of pregnancy, what surrounds the placenta?

A

Cytotrophoblast

50
Q

What holds blood vessels that supply the villi?

A

Chorionic plate

51
Q

What is the area where the embyro implanted called (end of 2nd month)?

A

Decidua basalis (interacts with chorion)

52
Q

What is the decidua capsularis?

A

The capsule part of the uterine lining

53
Q

What is destroyed at the end of the 3rd month?

A

Uterine cavity; chorion cavity

54
Q

What surrounds the yolk sac at the end of the 2nd month?

A

Chorionic cavity

Embryology (6 decks)

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