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MODULE 5 - Reproduction > EMBRYOLOGY - Embryonic Development > Flashcards

EMBRYOLOGY - Embryonic Development Flashcards

1
Q

What are capacitated sperm?

A

Capacitated sperm are hyper-motile sperm

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2
Q

Describe the process of sperm-ovum membrane fusion

A
  1. Capacitated sperm reach the ampulla
  2. Sperm move through the sticky matrix produced by the cumulus cells surrounding the ovum and interact with ZP3 proteins present on the zona pellucida
  3. Acrosome reaction occurs where the outer membrane of the sperm head dissolves to release proteolytic enzymes and uncover ZP2 receptors, allowing the sperm to penetrate the zona pellucida
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3
Q

What occurs within the ovum to achieve polyspermy block?

A

When the sperm penetrates the ovum, this stimulates calcium waves leading to a cortical granule reaction which hardens the zona pellucida. This prevents the penetration of other sperm, also known as polyspermy block

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4
Q

What is embryonic cleavage?

A

Embryonic cleavage is the development of the zygote into a multicellular complex within the zona pellucida

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5
Q

What are blastomeres?

A

The totipotent cells produced by embryonic cleavage of the zygote

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6
Q

When does the activation of the embryonic genome occur?

A

Activation of the embryonic genome occurs between the 4-8 blastomere stage

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7
Q

When does the morula stage occur?

A

Morula is formed at the 16 blastomere stage

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8
Q

Where within the female reproductive tract is a zygote cleaved into a morula?

A

The zygotę is cleaved into a morula while travelling down the oviducts towards the uterine horns

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9
Q

What happens to the morula to form a blastocyst?

A

The morula blastomeres form tight junctions with the adjacent cells and blastulation (fluid absorption) occurs to form a blastocoele (fluid-filled cavity). This structure is known as a blastocyst

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10
Q

What are the three features of the blastocyst?

A

Trophectoderm/Trophoblast
Inner cell mass (ICM)
Blastocoele

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11
Q

In the cow, which uterine horn can the blastocyst be found in?

A

The blastocyst is found in the same uterine horn as the corpus luteum

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12
Q

At which stage of embryo development do the blastomeres lose their totipotency?

A

Blastomeres lose their totipotency during blastocyst development

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13
Q

What is hatching?

A

Hatching is the process where the blastocysts emerges from the zona pellucida in order to continue development

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14
Q

What happens to blastocyst after hatching from the zona pellucida?

A

The blastocyst undergoes rapid proliferation of the trophectoderm cells to allow elongation of the blastocyst

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15
Q

In which species’ does the embryo elongate very rapidly after hatching from the zona pellucida?

A

Porcine and ruminant

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16
Q

Why does the embryo of the horse remain spherical rather than elongated after hatching from the zona pellucida?

A

The horse embryo remains spherical due to the embryonic vesicle (glycoprotein capsule) which forms around the trophectoderm

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17
Q

What is maternal recognition of pregnancy?

A

Maternal recognition of pregnancy is the prevention of luteolysis, ensuring the production of progesterone by the corpus luteum to support pregnancy continuation

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18
Q

Which cells secrete hormones to stimulate maternal recognition of pregnancy?

A

Trophectoderm cells

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19
Q

In which species is the maternal recognition of pregnancy not as important and why is this?

A

The bitch due to having such a long corpus luteum lifespan which spans across the entire gestation period

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20
Q

How do the ruminants prevent luteolysis in order to allow the continuation of pregnancy?

A

The ruminant trophectoderm cells secrete Bovine/Ovine trophoblast protein to inhibit the synthesis of prostaglandin F2α (PGF2α)

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21
Q

How does the sow prevent luteolysis in order to allow the continuation of pregnancy?

A

The sow trophectoderm cells secrete oestrodiol to redirect the endometrial secretion of prostaglandin F2α (PGF2α) into the uterine lumen where it will be metabolised

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22
Q

When would maternal recognition of pregnancy not occur in the sow even if she is pregnant?

A

Maternal recognition of pregnancy would not occur in the sow if there are less than three embryos present. The pregnancy would not be worth the metabolic demand and thus the pregnancy would be terminated

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23
Q

How does the mare prevent luteolysis in order to allow the continuation of pregnancy?

A

In the mare, the movement of the embryo around the reproductive tract stimulates a currently unknown hormone which prevents prostaglandin F2α synthesis

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24
Q

What is gastrulation?

A

Gastrulation is the phase in embryonic development when pluripotent stem cells differentiate into the three primordial germ layers

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25
Q

What are the three primordial germ cell layers?

A

Ectoderm
Mesoderm
Endoderm

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26
Q

Which structures develop from the ectoderm germ layer?

A

Epithelial surface (skin), Neural tissue

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27
Q

Which structures develop from the mesoderm germ layer?

A

Muscle, Bone, Blood, Connective tissue, Urogenital system

28
Q

Which structures develop from the endoderm germ layer?

A

Intestinal lining, Liver, Pancreas, Spleen, Trachea, Lungs, Heart

29
Q

Which cells migrate to the surface of the blastocyst to form the bilaminar embryonic disc?

A

Inner cell mass (ICM) cells

30
Q

What are the two layers of the bilaminar embryonic disc?

A

Epiblast
Hypoblast

31
Q

What is the difference between intra-embryonic and extra-embryonic?

A

Intra-embryonic: level of the embryonic disc
Extra-embryonic: level of the trophectoderm

32
Q

Which layer of the bilaminar embryonic disc will eventually form the intra-embryonic ectoderm germ layer?

A

Epiblast layer will eventually form the intra-embryonic ectoderm

33
Q

Which structure will eventually form the extra-embryonic ectoderm germ layer?

A

Trophectoderm layer will eventually form the extra-embryonic ectoderm

34
Q

Which layer of the bilaminar embryonic disc will eventually form the endoderm germ layer?

A

Hypoblast layer will eventually form the endoderm

35
Q

What is the extra-embryonic endoderm?

A

The extra-embryonic endoderm is a derivative of the hypoblast cells which have undergone extra-embryonic extension under the trophectoderm to form a continuous sheet lining the blastocoele (now known as the yolk sac)

36
Q

What is the primitive streak?

A

The primitive streak is a thickened region of the epiblast cells present on the dorsal surface of the embryonic disc

37
Q

(T/F) The primitive streak marks the cranial end of the embryo

A

FALSE. The primitive streak marks the caudal end of the embryo

38
Q

What is the name of the central groove of the primitive streak?

A

Primitive groove

39
Q

How can the primitive streak contribute to the formation of monozygotic twins?

A

Monozygotic twins can arise due to the incomplete separation of two primitive streaks on a single embryonic disc

40
Q

What is the mound of cells at the cranial end of the primitive streak called?

A

Primitive node

41
Q

Which structure is formed from the primitive node?

A

The notochord

42
Q

Which structures are formed from the notochord?

A

The notochord forms the mesoderm of the head and the neuro-ectoderm

43
Q

Describe the formation of the mesoderm layer

A

Epiblast cells migrate from the primitive streak and proliferate between the epiblast and hypoblast layers where they trans-differentiate into mesoderm cells, forming the mesoderm layer

44
Q

What are the two regions of the mesoderm?

A

Intra-embryonic mesoderm
Extra-embryonic mesoderm

45
Q

Where is the intra-embryonic mesoderm located?

A

The intra-embryonic mesoderm is continuous with the embryonic disc

46
Q

Where is the extra-embryonic mesoderm located?

A

The extra-embryonic mesoderm is continuous with the yolk sac

47
Q

Which regions of the embryonic disc are not populated by the mesoderm layer?

A

Buccopharyngeal membrane (mouth)
Cloacal membrane (anus)

48
Q

What is another term used to describe the trilaminar embryonic disc?

A

Trilaminar omphalopleure

49
Q

What are the three derivatives of the intra-embryonic mesoderm?

A

Paraxial mesoderm
Intermediate mesoderm
Lateral mesoderm

50
Q

Which structures are formed from the paraxial mesoderm?

A

Somites

51
Q

How can the somites be used to mark the stages of embryo development?

A

Somites are added caudally as the embryo develops

52
Q

What do the somites differentiate into?

A

Dermatome (subcutis)
Myotome (muscles, ligaments)
Sclerotome (vertebrae, bones)

53
Q

What is formed from the intermediate mesoderm?

A

Urogenital system

54
Q

What are the two layers of the lateral mesoderm?

A

Somatic layer
Splanchnic layer

55
Q

What is the fluid-filled space between the somatic and splanchnic layers of the lateral mesoderm?

A

Intra-embroyonic and extra-embryonic coelom

56
Q

What is formed from the intra-embryonic coelom?

A

The intra-embryonic coelom forms the body cavities (pleural and peritoneal)

57
Q

What is the embryonic structure that will eventually form the diaphragm?

A

Septum transversum

58
Q

What occurs if the septum transversum does not form?

A

The lungs will not develop leading to embryonic death

59
Q

What is the somatopleure?

A

The somatopleure is the layer of tissue comprising of the extra-embryonic ectoderm and the somatic mesoderm

60
Q

What is the splanchnopleure/allantois?

A

The splanchnopleure/allantois is the layer of tissue comprising of the extra-embryonic endoderm and the splanchnic mesoderm

61
Q

Which structure eventually forms the outer body wall (outer body tube) during tubulation?

A

Somatopleure forms the outer body wall during tubulation

62
Q

Describe the formation of the embryonic intestinal system (digestive tube)

A

The intra-embryonic mesoderm fuses to form the fore-gut and the hind-gut. The mid-gut is still continuous with the yolk sac via the umbilical stalk

63
Q

Describe the process of neural tubulation

A

Neuro-ectoderm cells fold upwards and fuse together to from the neural tube

64
Q

Where are the neural crest cells located?

A

The neural crest cells are found along the neural folds during neural tubulation

65
Q

Which structures are formed from the neural crest cells?

A

Heart connective tissues, parasympathetic and sympathetic ganglia, face and head structures

MODULE 5 - Reproduction (22 decks)

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