Lect. 17 - Extraembryonic Tissues And Placenta

Question 1

What germ layers are the extra embryonic layers derived from?

Answer 1

Amnion: ICM - epiblast derivative - ecto and meso
Yolk Sac: ICM - hypoblast derivative - endo and meso
Chorion: fetal maternal interface - ecto and meso
Allantois: ICM, interfaces w/ placenta - endo and meso

Question 2

What are the two trophoblastic derivative that comprise the fetal-maternal interface?

Answer 2

Placenta and chorion

Question 3

What are the functions of the amnion?

Answer 3

Buffer against mechanical injury; accommodates growth; allows normal movements; protects fetus from adhesions

Question 4

Hydramnios

Answer 4

Excessive amount of amniotic fluid (>2000 mL). Related to esophageal atresia and anencephaly

Question 5

Oliogohydramnios

Answer 5

Too little amniotic fluid (

Question 6

What info can be learned by testing for a-fetoprotein?

Answer 6

High concentration of a-fetoprotein is a strong indicator of NT defect

Question 7

What info can be learned by testing for creatine and lecithin-to-sphingomyelin ratio?

Answer 7

Fetal maturity can be assessed by determine the concentration of creatine or the lecithin-to-sphingomyelin ratio (reflection of the maturity of the lungs)

Question 8

What are the 4 extra embryonic layers?

Answer 8

Amnion, yolk sac, chorion, alantois

Question 9

Phase I of the formation of the amniotic fluid

Answer 9

1st 20 weeks of pregnancy; free diffusion of electrolytes through fetal ectoderm; maternal serum; secretion by amniotic membrane

Question 10

Phase II of formation of amniotic fluid

Answer 10

Contributions from fetal urine; filtration for vessels associated w/ chorion laeve (smooth chorion)

Question 11

Known and possible functions of the yolk sac in mammals?

Answer 11

May concentrate folic acid and vitamins A, B12, and E; other functions: site of origin of primordial germ cells; location of blood islands (origin of initial blood cells (extraembryonic hematopoiesis)

Question 12

Histiotrophic nutrition

Answer 12

Some evidence shows that before the placental circulation is established, nutrients (folic acids and vitamins) are concentrated in the yolk sac and are absorbed - happens during neurulation so may help prevent NTDs

Question 13

Meckel’s Diverticulum

Answer 13

Traces of the yolk duct persists as a fibrous cord or outpouching of the small intestine

Question 14

Where do their allantoic (umbilical) vessels develop?

Answer 14

In the mesoderm of the allantois

Question 15

Allantois

Answer 15

Proximal part of the allantois = urachus; associated w/ the formation of the urinary bladder; becomes the median umbilical ligament

Question 16

Hofbauer cells?

Answer 16

Fetal macrophages

Question 17

What tissue in the mature placenta directly interfaces w/ the maternal uterine CT?

Answer 17

Cytotrophoblast

Question 18

Chorionic plate

Answer 18

Extraembryonic mesoderm overlaid w/ trophoblast

Question 19

Hemochorial type

Answer 19

Villi and outer surface of chorionic plate are bathed in a sea of continually exchanging maternal blood

Question 20

Cytotrophoblastic shells

Answer 20

Formed by expansion of the cytotrophoblastic columns over the maternal decidual cells

Question 21

Anchoring villi

Answer 21

Villi that are anchored to the cytotrophoblastic shell (as opposed to floating villi)