Exam 4 - Extraembryonic Membranes

Question 1

List the 4 extraembryonic membranes

Answer 1

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

Question 2

Give 4 reasons as to why extraembryonic membranes are important

Answer 2

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

Question 3

What makes up the somatopleure of birds?

Answer 3

The ectoderm + the somatic plate mesoderm

Question 4

What happens to the somatopleure in birds?

Answer 4

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

Question 5

What makes up the splanchnopleure of birds?

Answer 5

The endoderm + the visceral plate mesoderm.

Question 6

What happens to the splanchnopleure in birds?

Answer 6

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

Question 7

How is the allantoic sac formed in birds?

Answer 7

Via evagination of the hindgut splanchnopleure

Question 8

What happens to the allantoic sac in birds?

Answer 8

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

Question 9

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

Answer 9

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

Question 10

What is the function of the allantoic sac in birds?

Answer 10

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

Question 11

What makes up the somatopleure in mammals?

Answer 11

the amniotic ectoderm + extraembryonic mesoderm

Question 12

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

Answer 12

via the umbilical cord

Question 13

What are the three sources of amniotic fluid?

Answer 13

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

Question 14

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

Answer 14

700-1000 mL every 3 hours.

Question 15

Oligohydramnios

Answer 15

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

Question 16

What are 9 significant functions of amniotic fluid in mammals?

Answer 16

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

Question 17

What is another name for the chorion in mammals?

Answer 17

cytotrophoblast

Question 18

Where does the cytotrophoblast layer come from?

Answer 18

It is the inner layer from when the trophoblast delaminates

Question 19

Where do chorionic villi come from?

Answer 19

They arise from the cytotrophoblast (chorion)

Question 20

What is the function of chorionic villi?

Answer 20

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

Question 21

How are umbilical vessels formed?

Answer 21

They are made from extraembryonic mesoderm inside of the connecting stalk

Question 22

What is the function of umbilical vesicles?

Answer 22

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

Question 23

Specifically, what does the umbilical vein do?

Answer 23

It obtains nutrients from the maternal blood supply

Question 24

Specifically, what do the umbilical arteries do?

Answer 24

They dispose of waste into the maternal blood supply

Question 25

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

Answer 25

Due to the fact that the embryo is growing

Question 26

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

Answer 26

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

Question 27

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

Answer 27

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

Question 28

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

Answer 28

It shrivels up

Question 29

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

Answer 29

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

Question 30

How is the umbilical cord in mammals formed?

Answer 30

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

Question 31

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

Answer 31

about 30,000

Question 32

What is considered to be critically premature for infant birth?

Answer 32

younger than 26 weeks.

Question 33

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

Answer 33

challenges in walking, talking, seeing, and hearing

Question 34

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

Answer 34

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

Question 35

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

Answer 35

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

Question 36

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

Answer 36

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

Question 37

What are the two primary goals in developing artificial wombs?

Answer 37

1. lowering death rate of premature babies | 2. reduce the estimated $43 billion that goes towards prematurity in the US each year

Question 38

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

Answer 38

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