Placenta and Fetal Membranes Flashcards
What are the fetal membranes?
Chorion
Amnion
Allantois
Umbilical vesicle
What makes up the fetal part of the placenta?
Chorionic sac - villous chorion
What makes up the maternal part of the placenta?
Derived from endometrium - decidua basalis
What is the outermost fetal membrane?
Chorionic sac
What occurs at the placenta?
Exchange of nutrients and oxygen between maternal and fetal bloodstreams
What connects the placental circulation with the fetal circulation?
Vessels in the umbilical cord
What are the parts of the Decidua?
- Decidua Basalis
- Decidua Capsularis
- Decidua Parietalis
What is the Decidua?
Functional layer of the endometrium
Decidua Basalis location?
Forms deep to conceptus (embryo) = placenta
What portion of the Decidua forms the maternal part of the placenta?
Decidua Basalis
Decidua Capsularis location?
Superficial and overlies the conceptus (embryo) = chorion
Decidua Parietalis location?
Remaining parts of the decidua = walls of uterus
During implantation, the trophoblast layer differentiates into what 2 layers?
Cytotrophoblasts (inner layer)
Syncytiotrophoblasts (outer layer)
What layer of cells displaces the decidual cells of the endometrium?
Syncytiotrophoblasts
Lacunae
Spaces that appear in the syncytiotrophoblasts that will fill with blood and secretions and eventually fuse
- diffusion of oxygen and nutrients here until actual circulation is formed!
What makes up the chorionic sac?
Extraembryonic somatic mesoderm
Cytotrophoblasts
Syncytiotrophoblasts
What is the amnion?
Membrane that surrounds embryo and amniotic fluid
What will the amnion eventually do and form?
Obliterate the chorionic cavity and form epithelial covering of the umbilical cord
What is the function of amniotic fluid?
Cushion and protect fetus and permit fetal movements
Does the volume of amniotic fluid increase as gestation continues?
Yes; should be around 700-1000 mL by week 37
Polyhydramnios
(include fetus and mother signs)
EXCESS amniotic fluid
- Fetus symptoms = CNS abnormalities
- Mother symptoms = breathlessness, pain, swelling, bloating
Oligohydramnios
(include fetus and mother signs)
Insufficient amniotic fluid (<400 mL)
- Fetus symptoms = anomalies like renal agenesis, not permitted to move very much
- Mother symptoms = abnormal placenta or HBP
The cytotrophoblasts proliferate towards the endometrium starting from where?
Chorionic plate
The cytotrophoblasts extend through what and attach to what?
Extend through syncytiotrophoblasts
Attach to decidua basalis
As the cytotrophoblasts proliferate and extend towards the decidua basalis, what will they form surrounding the chorionic sac?
Cytotrophoblastic shell