Fetal Membranes and Placenta

Question 1

what 3 decidual layers form

-when do they form and why?

Answer 1

1) decidua basalis: part of uterus where blastocyst implanted. forms maternal portion of the placenta (think base)

2) decidua capsularis: covers the outer edges of the developing fetus (think capsule)
- degenerates w/ development

3) decidua parietalis- uterine wall opposite of developing fetus
- degenerates with development

-endometrium prepares for implantation
this occurs during secretory phase (15-17)—->

Corpus luteum secretes progesterone causing further maturation of endometrium and spiral arteries

Question 2

when the blastocyst implants it develops what layers of the chorionic membrane?

Answer 2

when blastocyst is implanted- will have inner and outer cells

inner: closer to the fetus; somatic mesoderm
outer: trophoblastic cells; outer portion of chorionic membrane

Question 3

by the beginning of ___ the chorion will have developed lots of ___ composed of ____with each one surrounded by ___

Answer 3

by the beginning of the 2nd month, the chorion will develop lots of VILLI on its outer surface composed of a core of vascular MESODERM

-cytotrophoblastic cells surround each villi and these are in turn covered by the syncytium.

Question 4

where does the villous chorion form?

Answer 4

vili of chorion that are in contact with the decidua basalis grow and expand to form the villous chorion.

Question 5

what 2 things fuse to become the placenta?

Answer 5

decidua basal is from the mom and the villous chorion from the baby fuse to become the placenta

Question 6

what is the chorion laeve

Answer 6

the vascular villi that are not in contact with the uterus and these will degenerate

-this portion will expand and obliterate the decidua capsular that was originally surrounding it until it reaches and fuses with the uterine cavity wall

Question 7

how is maternal blood delivered to the placenta?

Answer 7

endometrial spiral arteries

Question 8

how does blood get released into the chorionic villi?

• what is the process called
• how is it important

Answer 8

process is called endovascular invasion:
-the trophoblastic cells undergo epithelial-mesynchamal transformation

-they move in and erode the lining of the spiral arteries, releasing blood into the area

this is important bc invasion limits the effects of vasoconstricing compounds and ensures adequate delivery of oxygen and nutrients to the mother

Question 9

early in pregnancy the placental barrier is composed of ____ and by the 2nd trimester, the ___ disappear

Answer 9

syncytiotrophoblast, endothelial cells, cytotrophoblast, and connective tissue

-connective tissue and cytotrophoblast disappear

Question 10

what travels from placenta to fetus to carry oxygenated blood?

Answer 10

umbilical VEIN

Question 11

how are hormones of pregnancy produced

Answer 11

the placenta acts as temporary endocrine organ

Question 12

the mature placenta has 2 sides:

Answer 12

1) maternal side: bordered by the decidua asalis

2) fetal side: bordered by the chorionic plate

Question 13

what are cotyledons

Answer 13

during the 2nd trimester. septa form the decidua basal is invaginate the region around the chorionic villi and help maximize surface area.

compartments on maternal side are called cotyledons

Question 14

initial formation of yolk sac occurs where and when?

-yolk sac is the early site of__ but this job is taken on later by ___

Answer 14

ventral aspect of the embryo

-early site of blood cell development, but later taken on by the liver and eventually bone marrow

Question 15

how is the primordial gut formed?

what should degenerate

Answer 15

embryo folds both laterally and cranial-caudally around the ventrally positioned yolk sac.

this pinches it and forms the primordial gut (early intestinal tube)

-the lighter part of the yolk save that remains after folding should degenerate or we get meckels diverticulum

Question 16

how is the amniotic fetal environment flushed every 3 hours?

Answer 16

fetus pees and the amniotic fluid is swallowed to open up the gut tubes and assist with development of the lungs

Question 17

amniochorion membrane

Answer 17

As stated earlier, this membrane eventually grows to contact the decidua parietalis, completely eliminating the uterine cavity

As the amnion grows to accommodate the growing fetus, it melds with the chorion laeve to form the amniochorionic membrane

Question 18

amniocentesis allows for-

Answer 18

genetic karyotyping, cell culturing, and measurement of alphafetoprotein concentrations (high levels are associated with neural tube defects, e.g. anencephaly & spina bifida, while low levels are associated with down syndrome/trisomy 21).

Question 19

Hydatidiform mole:
-partial
vs
complete?

Answer 19

a partial mole :2 male and 1 female pronucleus
-zygote will by 69 XYY or 69XXy triploid
-essentially a bundle of tissue that is completely fetus and may contain fetal hair/teeth/.
unrecognizable as a

Complete mole: 2 male pronuclei (no female)
-absolutely zero early transcription of embryonic genes and just an abnormally large placenta will be produced.

-complete mole fertilization errors can result in potentially fatal choriocarcinoma

Question 20

what are the 3 placental problems

Answer 20

1. placental abruption: separation of the chorionic plate from the endometrium with blood clots. this can lead to fetal death
2. placental previa: placenta partially covers the cervix. can lead to abruption
3. placenta acretia- implantation of the placenta into myometrium. baby must be delivered by hysterectomy

Question 21

polyhydramnios

Answer 21

amniotic fluid volume is too high. get developmental dysfunction

Question 22

oligohydramnios

Answer 22

volume of the amniotic fluid is too low, resulting in kidney malformation and placental malfunction

Question 23

amniotic band syndrome?

Answer 23

piece of amniotic sac breaks away and wraps around limb/cranium of fetus and can clear to amputation

Question 24

nuchal cord?

Answer 24

cord wraps around the fetus’s neck

Question 25

single umbilical artery

Answer 25

there should be 2, one from each iliac artery

Question 26

valamentous cord insertion?

Answer 26

umbilical inserts gtwn fetal membran (amnion and chorion) and vessels are not protected by whartons jelly therefore get damage

Question 27

erythroblastosis fetalis?

Answer 27

problem in the placental barrier where the blood mixes.

• can have ABO incompatibility or
• Rh factor (mom is Rh negative and baby is Rh positive)

Question 28

how do we get dizygotic twins

Answer 28

2 different zygotes are independently fertilized. placentas and chorion can fuse if implanted in proximity

-2 amnions and 1 or 2 placnetas and chorions

Question 29

how do we get monozygotic- diamniotic twins?

Answer 29

when inner cell masses separate two form 2 embryos.
65% of twins so majority

-have 2 amnions and 1 chorion.
but they can have 1 or 2 placentas bc they can share

Question 30

how do we get diamniotic dichorionc twins?

Answer 30

when there is separation in the morula phase therefore get separate implantation

35% of monozygotic twins

-get 2 of everything: amnion, chorion, placenta

Question 31

how do we get mono amniotic, monochorionic twins?

Answer 31

this is very rare
-single zygote separates one embryonic disc has formed.

this twin can share everything and be conjoined