Pathophys: Placenta and Meiosis: Natalia Flashcards
What is different about leptin in placentas of different organisms?
Rodents: placenta transport leptin across
Rheumanents: no transport, fetal adipose makes leptin
Primates: Placenta secretes leptin into maternal circulation, very little in fetal circulation
Objective: Understand early implantation
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Objective: Understand basic placental anatomy and circulation
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Objective: Placental oxygen and nutrient transfer
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Objective: to be able to describe some placental causes of second and third trimester vaginal bleeding
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What does blast-cyst mean?
Blast= cells with potential to differentiate cyst= cystic structure
What stage/day is blastocyst?
Stage 3 carnegie
Days 4-5
0.1-0.2 mm wide
What are the parts of the blastocyst?
Blastocyst cavity
Trophblast
Zona Pellucida
Embryoblast
What does the placenta come from?
Trophoblast
What does the trophoblast differentiate into?
Villous and extravillous cytotrophoblast cells
What does villous cytotrophoblast become? Extravillous?
Villous=syncytiotrophoblast cell
Extravillous=invasive trophoblast cell
What does the fetus come from?
Inner cell mass/embryoblast
What day does implantation take place?
Day 6-7
What allows for blastocyst adhesion to endometrium?
L-selectin system
TEST: hCG is a product of what cell type?
Trophoblast cells
What day does hCG production begin?
day 7, can detect 5 days prior to missed period
What is the early pregnancy test detecting?
Early pregnancy factor, not hCG… its not around yet
hCG stimulates what growth in endometrium?
Filopodia to help it connect and implant
EMPHACIZED: What is decidualization?
increase in vascular permeability and secretory activity of uterine stroma under conceptus
What does decidualization allow?
Access to maternal blood
When does decidualization occur?
as soon as 10 days after fertilization/ovulation
What happens to stroma in decid?
Surround Spiral arteries (progesterone)
When does the deciduaal reaction occur?
Every menstrual cycle due to progesterone
When does the decidua form?
When the embryo implants
How is a non receptive deciduaalized endometrium returned to normal with no pregnancy?
Menstruation
What is ironic about deciduaalization?
It eventually grows so large to block implantation
What does the deciduaa do?
allows efficient access to maternal blood
resists trophoblast invasion
provides nutrients
What invades?
Extravillous cytotrophoblast
What is the difference histologically between the cytotrophoblast and synticialtrophoblast?
Cyto=one nucleus
Syncytiotrophoblast=multiple nuclei
What invades the endometrial STROMA?
Syncytiotrophoblast
What is the main source of hCG in the placenta?
Syncytiotrophoblast
When are primary chorionic villi apparent?
By end of 2nd week
What makes primary chorionic villi?
Proliferation of cytotrophoblast extensions that grow INTO the syncytiotrophoblast
What is the villous cytotrophoblast?
Primary chorionic villi growing into the syncytiotrophoblast
What does the blastocyst look like on day 9?
Two layers surround:
Cyto: mononuclear
Syncytio: multinuclear
What are the two functions of the trophoblastic layers?
- draw nutrients
2. protect from maternal immune attack
HIV causes what in pregnant female?
Miscarriage
Preterm delivery
When does the blood flow in embryo start?
First heart beat
5 weeks of gestation
What has happened by the end of the third week?
Anatomy has lined up to allow nutrient exchange from mother to fetus:
Primary villi and mesenchyme have attached: This is SECONDARY Chorionic villi
What has happened by the end of the forth week?
Exchange begins in that anatomy
What happens in the fifth week?
First fetal heart beat
How long do the chorionic villi cover the sac?
Until the beginning of the eight week
How do the chorionic villi digress?
Choronic sac grows and clamps them down
They degenerate
SMOOTH chorion forms
What are the three deciduas?
Decidua:
basalis
capsularis
parietalis
What is the decidua vera?
Dec. capsulari+parietalis
Where is the parietalis? do other animals have it?
On wall of uterus
animals do not have it
When do we begin to be able to SEE the placenta?
4.5 weeks
EMPHACISED: What is the order of the layers of the placenta to uterus?
Placenta
Decidua
Myometrium
Do we need embryo to develop placenta?
No, placenta can develop on its own
What happens to spiral arteries when implantation occurs?
They get bigger to supply fetus:
What percent of maternal blood flow goes to fetus in pregnancy?
75%
What constitutes the chorion?
Trophoblastic layers
Extraembryonic somatic mesoderm
What forms the chorionic villi?What days?
cytotrophoblast
Days 13-14
What day does development of circulation begin?
Day 9-11
How does circulation begin?
- Lacunae in sycytiotrophoblast become filled with maternal blood and fuse to form lacunar networks
- cavity between embryblast and trophoblast forms the primordial amniotic cavity, lined by a membrane (amnio)
What forms the amnion?
Cavity between the embryoblast and trophoblast layers
TEST: What are the functions of the cytotrophoblast?
- Invasion
- Stem cells to make placenta
- invade uterine arteries
What is the key for fetal well being?
Circulation in villous space
TEST: How many discs does the human placenta have?
One disc placenta
What is the difference between the early to the late placenta cord?
Branching early
Non-branching late (less resistance)
What does decreasing branches do to blood flow?
Resistance is decreased with decrease in branches
What are the placental markers?
CD68
What are the blood vessel markers?
Factor VIII
What are the stroma markers?
Collagen IV
Vemintin
What are the syncytiotrophoblast markers?
Keratin
hCG
What happens if there is no enough remodeling of the placental exchange zone?
Not enough exchange
Or, too much pressure on
Where does nutrient and gas exchange occur?
Terminal villi
