Placentation Flashcards
Which species have a luteo-placental shift?
Horses, sheep, humans, cows
What is the luteo-placental shift
Shift in production of progesterone from luteal to placental
How does the luteoplacental shift affect the use of PGF2a to terminate pregnancy?
- If shift occurs, PGF2a can only be used to terminate pregnancy before the shift
- If there is no shift, then PGF2a can always be used to terminate pregnancy
What is a placenta?
The close attaachment of foetal membranes to the uterine wall to facilitate physiological exchange of gases, nutrients and waste products
Name the foetal membranes
- Amnion
- Yolk sac
- Allantois
- Chorion
Describe the amnion
- Innermost fluid filled membrane (reptile, bird, mammal)
- Allows symmetrical growth and protection of the foetus
- Temperature control and foetal movement
Describe the yolk sac
- Surrounds yolk in reptile and bird eggs
- In higher mammals has nutritional role in early pregnancy
Describe the allantois
- Sac from hindgut
- Connection to foetus becomes umbilical cor
- Collects waste products from foetus
Descibe the chorion
- Outer membrane
- Becomes foetal contribution to placenta
- All placentas are chorionic at some stage of development
What are the layers in the submucosa of the uterine wall?
Perimetrium, myometrium, endometrium
What are the 3 stages of implantation?
Apposition, adhesion, firm attachment or invasion of trophoblast into uterus
Describe apposition
Blastocyst or foetal membranes become closely apposed to uterine lining (epithelium)
Describe adhesion
Complex biochemical interaction between molecules on the trophoblast and epithlium
Outline firm attachment or invasion of trophoblast into uterus
On species, can be non-invasive or invasive
Describe non-invasive attachment of trophoblasts to uterus
- Cow, sheep
- Blastocyst undergoes elongation, long when attaches to uterus
- During apposition aligns with lining of uterus
- During attachment trophoblast layer in contact with uterine epithelium
Describe invasive attachment of trophoblasts to uterus
- Quickly after arrival of blastocyst to uterus
- Blastocyst remains spherical
- Invades uterine lining following apposition and attachment
What needs to occur to allow invasive attachment of the blastocyst?
- Specific window of time
- Presence of proteoglycan MUC1 needs to be down-regulated to allow attachment
What are the different methods of classification of placental structure?
- Foetal extraembryonic membranes
- Source of nutrition
- Maternal tissue shedding at birth
- Histological structure
- Macroscopic structure
What are the different types of nutrition possible in the placenta?
- Haemotrophic: nutrition from circulating maternal blood
- Histotrophic: nutrition from endometrium
What are the different types of maternal tissue shedding at birth?
- Deciduate vs non deciduate
- Deciduate: lining of uterus shed with lining of placenta at parturition
How can histological structure be used to calssifies placentas?
Different number of tissue layers interposed between maternal and foetal circulations
How can macroscopic anatomy of placentas be used for classification?
- Nutrient exchange areas
- Distribution of chorionic villi on chorionic sav and relationship with endometrium
- e.g. diffuse, cotyledonary, zonary
What are the placental classifications based on the number of tissue layers (Grosser classification)?
- Epitheliochorial
- Endotheliochorial
- Mesochorial
What are the 3 foetal layers of the placenta? (moving towards the maternal side)
- Foetal blood vessel endotehlium
- Foetal connective tissue/mesenchyme
- Foetal trophoblast