by mtoom


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What can lead to a small baby? (7)
  • Placental Insufficiency
    (Significant proportion of growth restricted fetuses are due to placental insufficiency)
     
  • Prematurity
  • Smoking
  • Maternal disease
  • Infection
  • Genetic
  • Constitutional
What are some important health implications of the placenta? (5)
  • Abortion and miscarriage
  • Fetal growth issues
  • Nutrition and oxygenation
  • Prematurity
  • Maternal risks
What are the main classes of things that can go wrong with a placenta? (3)

Abnormal placentation:
  • Inadequate implantation
    -Miscarriage
    -IVF failure
    -Fetal growth restriction
    -Pre-eclampsia 
  • Abnormal location
    -Ectopic
    -Previa 
  • Uncontrolled invasion
    -Accreta
    -Increta
    -Percreta
    -Gestational trophoblastic neoplasia 
What does it mean that the placenta is hemochorial? *
It means that the blood comes into direct contact with fetal trophoblast cells (chorion)
  • Placenta comes from cells from two distinct people (mom, fetus)
What 2 synchronous processes are required for implantation? * (2)
  • Uterine preparation
  • Embryo development and ability to interact with endometrium
Why do 50% of implantations fail at the critical time of implantation? (1)
Many reasons but often because of abnormal karyotype
When is the endometrium receptive to the blastocyst? (2)
  • Also, this correlates with levels of what hormone in the menstrual cycle?
  • 8-10 days after LH surge
  • 6-7 days after ovulation

Correlates with levels of progesterone
Describe the changes to the endometrium during uterine preparation (2)
  • Morphologic:
    -Increased cell size
    -Change in cell shape
    -Development of intracellular organelles (protein synthesis)
    -Formation of intracellular junctions
  • Functional:
    -Lipid and glycogen accumulation for energy
What are the 3 layers of the uterine lining (decidua)?
  • Describe their functions. 
  • Decidua parietalis
  • Decidua capsularis
    -Thin capsule of endometrium covering developing embryo 
  • Decidua basalis
    -Implantation site
    -Maternal portion of developing placenta 
Which two layers of the uterine lining join to form what? (2)
  • Decidua parietalis
  • Decidua capsularis

Join together to form the decidua vera
What is a placenta previa?
When placenta implants over the cervix
Where does the placenta usually implant? (1)
Fundus
What is it called when the placenta implants somewhere outside of the uterus? (1)
  • Cervix
  • Ovary
  • Fallopian tube
  • Abdominal cavity
  • Ampulla
  • Isthmus
  • Fimbrial 
Ectopic
Why is embryonic development critical in the formation of the placenta?
Because part of the placenta is fetal in origin
Where does fertilization usually occur? * (1)
Ampulla of fallopian tube
What happens to zygote if fallopian tubes are scarred due to PID?
Zygote may not make it down tube
By day 5 after fertilization, the blastocyst has developed what 3 parts?
  • Inner cell mass
    -Compacts to one side to form embryonic pole 
  • Fluid-filled cavity
    -Blastocele 
  • Outer cell mass
    -Trophoblast 
What are the 2 types of trophoblast?
  • Cytotrophoblast
    -Villus or extravillus cytotrophoblasts 
  • Syncytiotrophoblast
    -Giant, multinuclear cells formed by fusion of cytotrophoblasts
    -Invade into endometrium 
What cell type invades into the endometrium? (1)
Syncytiotrophoblast
What are the 3 stages of implantation?
  • Briefly explain these 
  • Apposition
    -Microvilli interdigitate with pinopodes on uterine epithelium 
  • Adhesion
    -Increased physical interaction between blastocyst and uterine epithelium 
  • Invasion
    -Blastocyst penetration of uterine epithelium 
Important, must know:
  • Name the 6 key steps that happen with the blastocyst within the uterine lining *
  • Invasion of endometrium by syncytiotrophoblasts
  • Further advancement of syncytiotrophoblasts and cytrophoblast columns
  • Lacunar spaces develop within syncytiotrophoblast layer
  • Cytotrophoblast columns extend to maternal spinal arteries
  • Villus columns extend laterally to form basal plate
  • Cytotrophoblasts invade into inner 1/3 of myometrium
Recap: Where do lacunar spaces develop?
Within syncytiotrophoblast layer
Recap: Where do cytotrophoblast colums extend to?
Extend to maternal spinal arteries
Recap: What happens when cytotrophblast columns reach maternal vessels in decidua?
They extend laterally to form basal plate
How does maternal blood flow through placenta?
  • Spurted out into lacunar spaces
  • Flows back into maternal veins
Is there autoregulatory/vasoactive control of maternal blood flow?
  • Why? 
No, because lacunar spaces cannot be physiologically controlled like a vessel
  • What cell types invade maternal spiral arteries?
  • What effect does this have? 
  • Cytotrophoblasts invade maternal arteries
  • "Hold open" the arteries to maximize bloodflow
Converts tight, thick-walled vessel into an open, capacitance vessel
What would be a normal versus shallow cytotrophoblast invasion?
Normal: Invasion into inner 1/3 myometrium
Name and explain clinical outcomes of shallow invasion of cytotrophoblasts (5)

Basically, the cytotrophoblasts didn't penetrate 1/3 of the myometrium and arteries remain sort of closed, so:
  • Growth restriction
  • Prematurity
  • Abruptio placenta
    -Bleeding from placenta that can happen with trauma 
  • Preeclampsia
    -Shallow invasion regulates mom's BP to some extent 
  • Stillbirth
Name and explain clinical outcomes of deep invasion of cytotrophoblasts (5)
  • Placenta accreta
    -Thru entire endometrium
  • Placenta increta
    -Into myometrium 
  • Placenta percreta
    -Past myometrium 
  • Maternal morbidity of bleeding
  • Fetal risks of bleeding & prematurity
What are risk factors for pathologic deep invasion? (2)
  • Prior C-section
  • Placenta previa

(or both!!)
What is a common complication of placenta accreta?
  • Postpartum hemorrhage

It often goes undiagnosed until birth...
What steps happen during placental maturation? (4)
  • Increased uterine blood flow
  • Extensive branching of villi
  • Increased surface area for exchange
  • Closer approximation of maternal and fetal blood flow
Where do the villi branch from?
Chorionic plate
  • Contains fetal arteries/veins 
What are the types of villi?
  • Stem villi
    -Support structure with central arteries and veins 
  • Intermediate villi
    -Immature: growth of villus tree
    -Mature: give rise to terminal villi 
  • Terminal villi
    -Final branch of villus tree, comprising 50% of villus SA
    -Extensive capillary network
    -Major site of exchange 
  • Anchoring villi
    -Extend to maternal surface, spread laterally to form basal plate 
What type of villi is the major site of maternal-fetal exchange? *
Terminal villi
What happens to the number of cell layers in early verus late pregnancy?
  • What effect does this have on circulations? 
Early pregnancy
  • 3 cell layers
  • Syncytiotrophoblasts, cytotrophoblasts, fetal capillary endothelium 
Late pregnancy (cytotrophoblasts are degenerated)
  • 2 cell layers
  • Syncytiotrophoblasts, fetal capillary endothelium

Number of cell layers is reduced, leaving a decreased distance between maternal and fetal circulations
Where is Wharton's jelly found?
Umbilical cord
Describe chorionic villi (4)
  • Fetal blood is within vessels in chorionic villi
  • Villi are bathed in maternal blood
  • Maternal blood is propelled into the intervillus space in jetlike streams traveling towards the chorionic plate
  • Blood percolates down around the villi to maternal venous drainage
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