Placenta Learning objectives

Question 1

Maternal component of the placenta

Answer 1

decidua basalis

Question 2

Formation of the chorionic villi

Answer 2

maternal capillaries near the synctiotrophoblast expand to form maternal sinusoids which anastomose with lacunae, filling them with blood. Cytotrophoblasts initiate formation of the chorionic villi

Question 3

layers of the placental membrane

Answer 3

1. Synctiotrophoblast
2. Cytotrophoblast
3. Extraembryonic mesoderm
4. Fetal endothelium
   - after month 4, cytotrophoblast and extraembryonic mesoderm degenerate

Question 4

Formation of chorionic laeve and frondosum

Answer 4

• chorionic villi on the embryonic pole proliferate as pregnancy advances, forming the chorionic frondosum (bushy chorion)
• Chorionic villi on the ab-ambryonic pole degenerate and form a smooth chorionic laeve by the end of month three

Question 5

Structures covered by the amnion

Answer 5

Embryo..? (someone else please edit this if you can find a better answer)

Question 6

origin of amniotic fluid

Answer 6

• Initially secreted by the cells of the amnion and some is derived from the maternal blood, tissue, and interstitial blood by diffusion
• by the beginning of the 11th week, the fetus contributes to the amniotic fluid by excreting urine into the amniotic cavity

Question 7

amnio-chorionic membrane

Answer 7

• comprised of both the amnion and the chorionic laeve

- develops from the increasing volume of amniotic fluid pushing the amnion against the amniotic laeve

Question 8

functions of amniotic fluid

Answer 8

1. Allows for fetal movements
2. prevents adherence between amnion and embryo
3. shock absorber
4. barrier to infection
5. promotes lung development

Question 9

amniocentesis

Answer 9

• test to study amniotic fluid that surrounds a baby
• a sample of amniotic fluid can be examined for:
  1. Genetic characteristics such as sex of baby
  2. Chromosomal problems such as Down syndrome or other birth defects
  3. Chemicals that show how mature the baby’s lungs are
  4. Infection

Question 10

What causes amniotic bands?

Answer 10

Tears in the amnion may result in amniotic bands that encircle the fetal limbs or digits resulting in deformations

Question 11

Polyhydramnios

Answer 11

• Excess amniotic fluid
• correlated with maternal diabetes and disorders of central nervous system and gastrointestinal tract (various atresias) that prevent the fetus from swallowing amniotic fluid

Question 12

Oligohydramnios

Answer 12

• too little amniotic fluid
• may result from failure of the kidneys to form
• Severe oligohydramnios in early pregnancy is a risk factors for lung hypoplasia (lung underdevelopment)

Question 13

Functions of the placenta

Answer 13

1. Acts as an organ of exchange between maternal an fetal tissues, providing nutrition, respiration, and excretion for the fetus
2. Produces hormones - progesterone, hCG, human placental lactogen = somatomammotropin
3. Serves as an immunological barrier between maternal and fetal tissues

Question 14

Fetal component of the placenta

Answer 14

Villous chorion

Question 15

anatomy of the umbilical cord

Answer 15

2 arteries and 1 vein
arteries are deoxygenated blood
vein is oxygenated from mother
wharton’s jelly

Question 16

Wharton’s jelly

Answer 16

surrounds umbilical cord. temperature sensitive

Question 17

what happens to the placenta at about 10 weeks

Answer 17

amnion fuses with chorion

Question 18

En caul delivery

Answer 18

sac still in tact

Question 19

Placental delivery orientation

Answer 19

placenta turns inside out so that fetal side is showing, must rotate in order to release all cotyledons to prevent excessive bleeding of uterus

Question 20

Four functions of the placenta

Answer 20

Endcorine, metabolism, exchange, isolation

Question 21

Endocrine function (what is secreted)

Answer 21

hCG
Relaxin
Estrogen and Progesterone
Human placental lactogen

Question 22

Metabolic products of placenta

Answer 22

Glycogen

Cholesteral

Question 23

Exchange for placenta

Answer 23

Simple diffusion (gasses, water, drugs)
Facilitated diffusion (glucose, some drugs)
Active transport (amino acids)
Pinocytosis (antibodies)

Question 24

Isolation functions

Answer 24

Don't want mother and fetal blood to mix
thwarted by microbreaks
rubella
lysteria
fetal blood cells

Question 25

Rh disease

Answer 25

mother is Rh- and father is Rh+, mother will not have the antigen, so if baby produces it (is Rh+), the mother will make antibodies that will attack the baby (more common in second pregnancy)
causes erythroblastosis fetalis

Question 26

Erythroblastosis fetalis

Answer 26

severe fetal anemia, like CHF, baby hydropic

Question 27

Prevention of Rh disease

Answer 27

Rhogam, antibodies against Rh protein, and hides the fetal Rh+ from mother, she does not make her own antibodies
28 weeks, works up to 72 hrs

Question 28

leaving cotelydons behind in pregnancy

Answer 28

continuing bleeding of uterus, hemmorhage in 10 minutes

Question 29

Marginal insertion

Answer 29

Battledore

small fetus

Question 30

Membranous or velamentous

Answer 30

nonreassuring fetal heart tracing

kinks

Question 31

Accessory Lobe

Answer 31

aka succinturiate lobe
could leade to vasa previa
veins before birth

Question 32

Vasa previa vs placenta previa

Answer 32

if water breaks, vessels could burst. vessels first
loss of fetal blood rapidly. depends on outlook of pregnancy whether it will be c-section or natural.

placenta out first. c-section

Question 33

Accreta, Increta, percreta

Answer 33

accreta-too strongly to uterine wall or myometrium
increta-invades into myometrium
percreta-into bowel or bladder
results in tremendous blood loss and needs to be treated before labor

Question 34

aburption

Answer 34

premature placenta shedding
cocaine
blood clot
baby’s oxygenation low

Question 35

Kidney disfunction in fetus

Answer 35

could lead to improper lung development (urine contains lung growth factors)

Question 36

Polyhydroamnios

Answer 36

infant has problem swallowing

maternal diabetes

Question 37

Oligohydramnios

Answer 37

ruptured membranes
poor fetal urine output
absent fetal urine output

Question 38

Functions of amniotic fluid

Answer 38

cushion
allows for movement (musculocutaneous growth)
contains growth factors for lungs (in urine)