Lecture 13: Extraembryonic Tissues & Placenta Flashcards
What are the amnion and yolk sac derivatives of?
Amnion: epiblast
Yolk sac: hypoblast
Name the extraembryonic tissues.
Amnion, Yolk sac, Chorion, & Allantoes
What do the chorion and allantois interface with?
Chorion: part of fetal maternal interface
Allantois: placenta via umbilical cord
What two things make up the fetal-maternal interface?
Placenta and Chorion
What are functions of the amnion?
Buffer against mechanical injury, Accommodate growth, Allow normal movements, & protect fetus from adhesions
High levels of alpha-fetoprotein are strong indicators of _____.
Neural tube defects
Creatinine or Lecithin-to-sphingomyelin ration can be used to determine what?
Fetal maturity based on maturity of lungs
What is hydramnios frequently associated with?
Esophageal atresia or anencephaly
What is oligohydramnios frequently associated with?
Renal agenesis
What occurs during phase I of amniotic fluid formation?
Diffusion of electrolytes through fetal ectoderm, maternal serum added, secretion by amniotic membrane
What occurs during phase II of amniotic fluid formation?
Fetal urine added & filtration for vessels associated with chorion leave
What is the turnover rate of amniotic fluid in the 3rd trimester and at term?
3rd trimester: every 3 hours
Term: 500 mL/hour
Folic acid and vitamins A, B12, and E may concentrate where?
Yolk sac
Where is the site of origin of primordial germ cells and the location of blood islands?
Yolk sac
What is histiotrophic nutrition?
Endocytosis of folic acid and vitamins A, B12, & E in the yolk sac
What is Meckel’s Diverticulum?
a remnant of the yolk duct that appears as a fibrous cord or out-pouch of the small intestine
Where do allantoic vessels form?
Mesoderm of allantois
The proximal part of the allantois is also known as _____ and associated with formation of the _____. It then becomes the _____.
Urachus.
Urinary bladder.
Median umbilical ligament
In the previllous embryo _____ villi have formed on the trophoblast.
No
In the primary villi stage _____, _____, _____primary villi appear.
Solid, cytotrophoblastic, ectodermal
In the secondary villous stage, _____ appear within the primary villi.
Mesodermal cores
In the tertiary villous stage _____ appear in the mesenchymal core of the secondary villi.
Blood vessels
What are hofbauer cells?
Fetal macrophages
What do cytotrophoblastic columns do?
Hold placenta in place
What is the chorionic plate VS the cytotrophoblastic shell?
Chorionic plate: fetal side.
Cytotrophoblastic shell: covers maternal decidual shells on maternal side
Which genes are expressed while the placental villi are being established?
Msx2 & Dlx4
The exit from the cell cycle at points of branching on villi is due to what?
Transcription factor Gem-1
What are the layers from amnion to outer cytotrophoblastic shell?
Amion–>Chorionic cavity–>Chorionic plate–>Villi–>Syncytiotrophoblast–>Outer cytotrophoblastic shell
What is the chorionic leavae?
Area where villi go away because they’re not being used
What is the pathway of maternal blood flow?
Enters trophoblastic lacunae–>exchange of materials with fetal blood in capillaries–>Exits maternal veins in decidua basalis
What is the pathway of fetal blood flow?
Enters capillary beds in villi via umbilical arteries–>Exchange of materials with maternal blood–>Exits capillary bed via umbilical vein
