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Embryology > Lecture 15 - Post-implantation + Placenta Development > Flashcards

Lecture 15 - Post-implantation + Placenta Development Flashcards

1
Q

What does the zona pellucida prevent the embryo from doing?

A

Adhering to anything other than the uterus

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2
Q

What does the embryo do when it reaches the uterus?

A

It “hatches” from the zone pellucida in order to attach itself to the uterine wall

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3
Q

What does the blastocyst adhere to?

A

The endometrium

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4
Q

What is the endometrium?

A

The epithelium lining the inside of the uterine wall

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5
Q

What is an ectopic pregnancy? List 3 types

A

Implantation of the embryo in an inappropriate/abnormal location

Tubal - uterine tubes
Ovarian - ovaries
Abdominal - abdominal cavity

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6
Q

What is placenta previa?

A

Implantation occurring near the cervix of the uterus, resulting in a low lying placenta next to (partial/marginal previa) or covering (complete previa) the cervix

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7
Q

How is the extra-embryonic mesoderm formed?

A

Cells migrate to become placed between the trophoblast and the membrane surrounding the yolk sac as well as the amnion

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8
Q

What is the extra-embryonic coelom and how is it formed?

A

A series of cavities form within the extra-embryonic mesoderm

The cavities grow in size until they eventually come together to form a single large cavity, which is the extra-embryonic coelom

The extra-embryonic coelom is completely surrounded by embryonic mesoderm

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9
Q

What is the mesodermal stalk? What does it give rise to?

A

The mesodermal stalk connects the embryo, amnion and yolk sac with the extra-embryonic mesoderm and trophoblast

It eventually becomes the umbilical cord

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10
Q

How does the blastocyst align itself when implanting?

A

It alligns itself with the inner cell mass facing the wall of the uterus

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11
Q

How does the embryo implant itself into the uterine wall?

A

Enzymes secreted by the embryonic trophoblast digest epithelium of the uterus and the ECM of the uterine wall

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12
Q

What is the difference between the endometrium and decidua?

A

Once implanted, the endometrium is referred to as the decidua

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13
Q

What does the trophoblast secrete? What does this do?

A

The trophoblast secretes human chorionic gonadotrophin (hCG) which prevents further menstruations

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14
Q

What does the trophoblast differentiate to become? (2)

A

Cytotrophoblast (cellular trophoblast)

Syncytiotrophoblast (syncitial trophoblast)

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15
Q

What is different about the syncytiotrophoblast when compared to the cytotrophoblast?

A

The syncytiotrophoblast undergoes nuclear division but no cytoplasmic division, resulting in a syncytium (multiple nuclei in a single cytoplasmic mass)

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16
Q

What is a lacunae?

A

Large openings/cavities formed in the uterine tissue into which maternal blood leaks into

17
Q

Diffusion of gases, nutrients and wastes to/from embryonic blood occurs in structures associated with _____

A

Lacunae

18
Q

What three layers form the chorion?

A

Syncytiotrophoblast
Cytotrophoblast
Extra-embryonic mesoderm

19
Q

Where is the chorion found?

A

The chorion surrounds the embryo/fetus

20
Q

What two components make up the placenta? Which one is the embryonic component and which one is maternal?

A

Chorion (embryonic) + decidua basalis (maternal)

21
Q

What is the function of the placenta?

A

Allows for exchange of nutrients + waste between the embryo and the mother

22
Q

What is the difference between a primary and secondary chorionic villus?

A

The primary and secondary villi both possess syncytiotrophoblast surrounding cytotrophoblast, but in the secondary villus there is also a core of extra-embryonic mesoderm

23
Q

What does the extra-embryonic mesoderm create in the core of a chorionic villus?

A

Blood vessels
Capillaries
Blood cells

24
Q

What structure connects the embryo/foetus to the placenta? What is it formed from?

A

The umbilical cord - formed from the embryonic stalk

25
Q

List the 3 extra-embryonic structures

A

The amniotic sac

The yolk sac

The allantois

26
Q

What is the structure + function of the amniotic sac

A

Structure: amniotic cavity roof: amnion (squamous cells of epiblast origin), floor: epiblast proper. Filled with amniotic fluid, wraps around embryo during embryonic folding, forming amniotic sac

Function: prevents embryo from drying out, storage for metabolic residues, protective structure (shock absorption)

27
Q

What is the function of the yolk sac?

A

Produces cells that will form the embryo’s primordial germ line that will migrate into the developing reproductive system to form sperm + egg mother cells

Contains precursors for blood cells

Provides nutrition for the first 2/3 weeks of development

28
Q

What do the vitelline arteries eventually fuse to become?

A

The arteries that supply the dorsal mesentery of the gut

29
Q

Describe the formation and function of the allantois

A

When the cloacal membrane is formed, a small sac evaginates from the yolk sac - allantois

Waste storage + gas exchange (vestigial in humans because waste and gas exchange can occur in the placenta and mother’s blood)

Becomes surrounded by stalk of extra-embryonic mesoderm; contributes to umbilical cord formation

Walls well-vascularised; blood vessels contribute to umbilical arteries + veins - umbilical circuit

30
Q

Describe the structure and function of the umbilical cord

A

2 arteries, 1 vein

Umbilical artery: brings oxygen+nutrient poor blood to the placenta

Umbilical vein: brings oxygen + nutrient rich blood to the sinus venosus of the heart

31
Q

What happens to blood entering the heart from the placenta?

A

Rich blood from the placenta is mixed with poor blood from the cardinal veins

32
Q

What does the left umbilical artery eventually do?

A

Loses connection with heart, carries blood to developing liver instead (which metabolises the rich nutrients)

Embryology (5 decks)

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