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VMS 1007 > Embryo development and placentation > Flashcards

Embryo development and placentation Flashcards

1
Q

What is fertilisation?

A

Union of a haploid oocyte and a haploid spermatozoon to produce a diploid zygote

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2
Q

What marks the end of fertilisation?

A

The initiation of zygote cell division/ cleavage

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3
Q

What is a morula?

A

8 cell embryo

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4
Q

What happens when the morula becomes compacted?

A

Forms two layers, the outer cells differentiate to become early trophoblasts and the inner cells stay as a discrete cluster

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5
Q

What is another name for the inner cells?

A

Inner cell mass

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6
Q

What is the blastocoel ?

A

Fluid-filled yolk cavity/ space that forms inside the blastocyst during early embryonic development

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7
Q

What do the trophoblasts give rise to?

A

The fetal membranes (chorion and amnion)

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8
Q

What do the inner membranes give rise to?

A

Becomes the inner cell mass which forms the embryo itself and two fetal membranes

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9
Q

What is hatching?

A

The pressure on the zona pellucida increases, trophoblasts release proteases which weaken the wall

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10
Q

What is the placentae?

A

region of apposition between uterine lining and fetal membranes where metabolites are exchanged

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11
Q

What are some of the functions of the placenta?

A

Fetal nourishment, waste removal and production of hormones

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12
Q

What is the diffuse placental type?

A

Exchange occurs across the whole surface area of the placenta (e.g in pigs)

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13
Q

What is the zonary placental type?

A

Exchange occurs across bands of the placenta (e.g in carnivores)

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14
Q

What is the discoid placental type?

A

Exchange occurs across one circular section of the placenta (primates and rodents)

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15
Q

What is the name of each daughter cell of the ‘cleavage’ process?

A

A blastomere

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16
Q

What is the purpose of the outer blastomeres becoming flattened and forming tight junctions?

A

It reduces fluid permeability

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17
Q

What do the outer and inner blastomeres look like in a morulla?

A

Outer look compacted, as they begin to form trophoblasts
The inner cells stay as discrete clusters

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18
Q

What do trophoblasts create in the middle of the blastocyst?

A

The Blastocoele, which is a fluid filled cavity

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19
Q

What are trophoblasts destined to form?

A

The chorion and the amnion which are fetal membranes of the conceptus

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20
Q

Why do inner blastomeres form gap junctions and what are they destined to become?

A

Inner blastomeres form gap junctions to maximise intercellular communication and they are destined to become inner cell mass which then goes on to form the embryo itself

21
Q

How does the hatching of the blastocyst occur?

A

Blastocyst pumps fluid into the blastocoele, this causes pressure on the zona pellucida
Zona pellucida breaks down and the blastocoele bursts

22
Q

What is the difference between embryo development in primates and domestic mammals?

A

In primates the embryo implants rapidly, and extra-embryonic membranes form later
In mammals the extra-embryonic membranes form during a prolonged pre-attachment period

23
Q

How does the yolks sac form?

A

Primitive endoderm migrates down over inner cell region which forms the first membrane ‘the yolk sac;

24
Q

What is a placentome?

A

A discreet area of interdigitation between a maternal caruncle and a fetal cotyledon

25
Q

What is a maternal caruncle?

A

The maternal side of the placenta

26
Q

How does the embryo signal to the mother that it is present?

A

The embryo prevents luteolysis of the corpus luteum, the corpus luteum releases progesterone which prevents ovulation

27
Q

What is the main maternal recognition of pregnancy in the pig?

A

The conceptus secretes oestradiol,
contraction of the uterus muscles which causes pgf2a to be wafted away into the lumen of the uterus where it can’t do anything

28
Q

What does contraction of the uterus due to oestradiol do in pigs?

A

Wafts away pgf2a as well as making sure that there is equal distribution of the conceptus’s along the uterine horn

29
Q

How many conceptuses in each uterine horn of the pig is required for their to be sufficient oestradiol secretion for contraction?

A

A minimum of two conceptuses in each uterine horn

30
Q

What is the chorionic girdle and what animal is it found in?

A

Chorionic girdle is an area of specialised trophoblast cells that form the chorionic girdle- it is found in horses

31
Q

What is the function of the chorionic girdle?

A

It forms endometrial cups which secrete ecG and induces ovulation and formation of the secondary corpus luteum

32
Q

What is the purpose of the chorion?

A

It is a membrane that surrounds the fetus and helps exchange nutrients, gases etc.

33
Q

What is the function of prostaglandin f2 alpha?

A

It releases oxytocin which causes a positive feedback effect leading to the breakdown of the corpus luteum

34
Q

Which animal produces interferon tau?

A

Ruminants

35
Q

What is the function of interferon tau?

A

It acts on the endometrial cells of the uterus to block oxytocin receptors (so no pathway that breaks down the corpus luteum

36
Q

What area produces interferon tau?

A

It is produced by the blastocyst

37
Q

What is the secondary function of inteferon tau?

A

Helps promote the attachment of the embryo to the uterus

38
Q

What initiates luteolysis, what subervts it and why?

A

Luteolyis is initiated by uterine release of prostaglandin f2 alpha
The embryo subverts this as we need progesterone to signal to the mother that it is there

39
Q

Where does a cotyledon originate from?

A

has foetal origin

40
Q

Where does a caruncle originate from?

A

Has maternal origin

41
Q

Where does the chorion and amnion originate from?

A

trophoblast and mesoderm

42
Q

Where does the yolk sac originate from?

A

Endoderm

43
Q

Where does the allantois originate from?

A

Mesoderm

44
Q

What is the name for the new layer of cells formed from the inner cell mass

A

The new layer of cells that forms the yolk sac (endoderm) is called the hypoblast
The remaining ICM is called the epiblast

45
Q

What is the allantois an ‘out-pushing’ of?

A

The primitive gut

46
Q

What species have an epitheliochorial barrier?

A

Horses, pigs ruminants

47
Q

What species have an endothelial barrier?

A

Carnivores

48
Q

What species has a hemochorial barrier?

A

Primates/ Humans

VMS 1007 (30 decks)

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