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Embryology > Exam 4 - Extraembryonic Membranes > Flashcards

Exam 4 - Extraembryonic Membranes Flashcards

1
Q

List the 4 extraembryonic membranes

A
  1. amnion 2. chorion 3. yolk sac 4. allantoic sac
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2
Q

Give 4 reasons as to why extraembryonic membranes are important

A

They provide: 1. protection 2. nutrition 3. respiration 4. excretion

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3
Q

What makes up the somatopleure of birds?

A

The ectoderm + the somatic plate mesoderm

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4
Q

What happens to the somatopleure in birds?

A

It lifts up and fuses on the dorsal side of the embryo resulting in two coverings for the embryo - the amnion and the chorion

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5
Q

What makes up the splanchnopleure of birds?

A

The endoderm + the visceral plate mesoderm.

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6
Q

What happens to the splanchnopleure in birds?

A

It surrounds the yolk, forming the yolk sac, which retains a connection to the gut

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7
Q

How is the allantoic sac formed in birds?

A

Via evagination of the hindgut splanchnopleure

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8
Q

What happens to the allantoic sac in birds?

A

It pushes into the extraembryonic (chorionic) coelom to surround the entire embryo

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9
Q

What are some of the functions of amniotic fluid in birds?

A
  1. shock absorption
  2. source of heat capacity
  3. avoids dehydration
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10
Q

What is the function of the allantoic sac in birds?

A

It collects waste and allows for gas exchange because it contains blood vessels.

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11
Q

What makes up the somatopleure in mammals?

A

the amniotic ectoderm + extraembryonic mesoderm

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12
Q

In mammals, the amnion surrounds the embryo, how is it attached to the embryo?

A

via the umbilical cord

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13
Q

What are the three sources of amniotic fluid?

A
  1. initially, it mostly is diffused into the embryo from the endometrium
  2. when the embryo’s circulatory system is set up but skin is not yet keratinzed, amniotic fluid will ooze out of the embryo
  3. later, the embryos mucous membranes contribute to the fluid
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14
Q

How much and how often is amniotic fluid produced and removed?

A

700-1000 mL every 3 hours.

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15
Q

Oligohydramnios

A

If urinary tract of the embryo is not working their will be too little amniotic fluid

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16
Q

What are 9 significant functions of amniotic fluid in mammals?

A
  1. symmetrical external growth of embryo
  2. barrier to infection
  3. permits “practice” for internal systems
  4. prevents adherence of amnion to embryo
  5. cushions the embryo
  6. maintains a constant temp
  7. allows for fetal movement, promoting muscle development
  8. assists in maintaining fluid and electrolytes
  9. filter between maternal and fetal circulation
17
Q

What is another name for the chorion in mammals?

A

cytotrophoblast

18
Q

Where does the cytotrophoblast layer come from?

A

It is the inner layer from when the trophoblast delaminates

19
Q

Where do chorionic villi come from?

A

They arise from the cytotrophoblast (chorion)

20
Q

What is the function of chorionic villi?

A

They reach through the syncytiotrophoblast layer and into the endometrium providing an access to pools of maternal blood

21
Q

How are umbilical vessels formed?

A

They are made from extraembryonic mesoderm inside of the connecting stalk

22
Q

What is the function of umbilical vesicles?

A

To provide a connection between the embryonic circulatory system and chorionic villi

23
Q

Specifically, what does the umbilical vein do?

A

It obtains nutrients from the maternal blood supply

24
Q

Specifically, what do the umbilical arteries do?

A

They dispose of waste into the maternal blood supply

25
Q

Why does the cavity between the amnion and the chorion eventually disappear?

A

Due to the fact that the embryo is growing

26
Q

Why is it not a problem that the embryo eventually bulges our of the endometrium and into the uterine cavity?

A

Because contact between the chorionic villi and the endometrium is still maintained at the placenta

27
Q

Even though people think that the yolk sac is evolutionary junk it is actually quite useful, list 4 of its functions

A
  1. involved in the transfer of nutrients between endometrium and embryo’s gut
  2. blood initially develops in the EE mesoderm on the outside of it
  3. The endoderm of the umbilical vesicle migrate into embryo’s gut creating buds and branches
  4. primordial germ cells originate here and migrate to become gonads
28
Q

What happens to the yolk sac once it has served its function and is no longer needed?

A

It shrivels up

29
Q

Even though evagination of the hindgut occurs to produce the allantoic sac it does not expand to surround the embryo in mammals, why?

A

Because respiratory and excretory functions are already being performed at the placenta so it is not necessary

30
Q

How is the umbilical cord in mammals formed?

A

As a result of ventral closure which squeezes the EE membranes and umbilical vessels in to one cord, connecting stalk

31
Q

How many babies are born prematurely each year in the USA?

A

about 30,000

32
Q

What is considered to be critically premature for infant birth?

A

younger than 26 weeks.

33
Q

If critically premature babies survive, what challenges do they often experience?

A

challenges in walking, talking, seeing, and hearing

34
Q

How old were the lamb fetuses used in the testing of artificial wombs?

A

105-115 days which is roughly equivalent to a 23-week old human

35
Q

What is one of the primary reasons that preterm birth is so dangerous?

A

Because once the baby takes its first breath of air, the development of lungs is halted

36
Q

List 3 benefits of an artificial womb over an incubator for preterm babies?

A
  1. boost lung growth
  2. protect the baby from infection
  3. support intestinal development
37
Q

What are the two primary goals in developing artificial wombs?

A
  1. lowering death rate of premature babies

2. reduce the estimated $43 billion that goes towards prematurity in the US each year

38
Q

What hope can pro choice advocates see upon development of an artificial womb?

A

It could encourage states to curtail abortions to 20 weeks gestation, since hopefully embryos that young could survive within an artificial womb.

Embryology (8 decks)

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