Placental Development Flashcards
What does the outer layer of trophoblast cells become? (2)
Placenta and chorion
What does the trophoblast cells produce?
HCG (Human Chorionic Gondatrophin)
What is the role of HCG in placental development?
To maintain the endometrium by ensuring the continued production of progesterone.
What does the inner cell mass become? (3)
Fetus, cord and amnion.
At term, what is the length, width and weight of the placenta?
20cm long
2.5cm thick
600g weight
Where does implantation of the placenta usually occur?
At the fundus - wither ANT/POST
What are the 5 key functions of the placenta?
Respiration
Nutrition
Excretion
Protection
Hormone Production
What is the placenta derived from?
Embryonic trophoblast cells.
What are the initial trophoblast cells called as a collective? Then what does this differentiate into?
Cytotrophoblast
It differentiates into a syncytiotrophoblast
What happens during placental development implantation?
- What does the blastocyst develop?
- Where is the embryo suspended?
- The blastocyst begins to develop finger-like projections from the trophoblast all over the surface.
- These are the developing chorionic villi. (primary cv)
- The embryo is suspended in the chorionic sac at this point.
What does the syncytiotrophoblast invade? What does this allow the embryo to do?
The uterine lining. (This allows to embryo to embed by day 10)
What happens during the development of the chorionic villi on the 3rd week?
- 3rd week - embryonic mesenchyme invades the primary chorionic villus to form secondary chorionic villi.
(Some of the mesenchyme cells in the core differentiate into FETAL BLOOD CAPILLARIES)
What happens during the development of the chorionic villi by day 20?
There is a functioning arteriocapillary venous network connected to embryonic heart vessels.
What happens during the development of the chorionic villi by the end of the 3rd week?
- Blood circulates through the chorionic villi.
- Exchange os substances between the maternal and feral circulation systems begin.
At the same time as chorionic villi development, what do the cytotrophoblasts do?
- They proliferate and extend through the synciotrophoblast.
-This forms the cytotrophoblast shell.
Once the cytotrophoblast cell is formed, what does it cause the chorionic sac to attach to?
- The maternal endometrium by anchoring villi.
- From the sides of the anchoring villi, villi branch and grow.
(Main exchange between maternal and feral circulation)
Once the (embryo) conceptus has implanted, what does the endometrium become known as?
The decidua.
What happens to the decidua at the end of pregnancy?
It will shed.
What are the 3 regions of the decidua?
- The decidua basalis
- The decidua capsularis
- The decidua vera
Where is the decidua basalis located ?
What does it form?
- Lies beneath the embryo, forming the maternal component of the placenta?
Where is the decidua capsularis located?
- Overlies the embryo/conceptus
Where is the decidua vera located?
- The remaining of the uterine lining.
SEE LATER DEVELOPMENT IN NOTES
:)
What happens to the placenta by 16 weeks?
- Placenta reaches its full thickness.
- Circumferential growth continues (villi branch).
- Size/Number of maternal capillaries increase.
- SA increases for gaseous exchange.
What is the scientific word for lobes?
Cotyledons
How many lobes are on the maternal side of the placenta? What separates them?
- 20
- Sulci
What are cotyledons (LOBES) made up of?
- Lobules (each containing a single villi with branches)
What colour is the maternal side of the placenta?
Dark red (due to maternal blood).
What is the role of the amnion on the fetal side of the placenta?
- Covers outer surface of umbilical cord
- Produces AMNIOtic fluid
What is the role of the chorion on the fetal side of the placenta?
- Loosely lines the decidua
What is the amnion derived from?
- Inner cell mass.
What is the chorion derived from?
Trophoblastic layer of placenta.
What does the amnion look like on the fetal side of the placenta? STT
- Single layer
- Smooth, tough, translucent
What does the chorion look like on the fetal side of the placenta?
- Outer membrane
- Rough, thick, opaque, friable
Which membrane is closest to the foetus?
- The amnion
How is amniotic fluid recycled by the foetus?
- Fetal swallowing and urine
What are fetal lungs full of?
- Amniotic fluid
What are the 5 main functions of amniotic fluid?
- Cushions (from pressure of uterine walls)
- Growth
- Movement
- Protection from noise
- Temp
What does the umbilical cord contain?
- x 2 arteries
- x 1 vein
- Wharton’s jelly
What types of medications can cross the placenta?
- Illegal substances - withdrawal
- Opioids (pethidine/ codeine)
- Antidepressants
- Antibiotics
