Placenta specific Flashcards
Placental types by chorionic villi distribution
Placentae (plural) can be classified by the distribution of villi on the surface of the chorion
DIFFUSE
- Even distribution of villi across the entire chorioninc surface
Cotyledonary
- Discrete round patches of villi form cotyledons on the chorion
- Connected to endometrial carunclex Zonary
- Prominent round transfer zone of villi as a central band
- Edges of band form pigmented zone, containing haemorrhage and necrotic tissue
DISCOID
- Discrete disc of villi on one side
Pick placenta type
Bottom left = zonary
2nd = diffuse (if can’t see anything)àhorse
3rd = Discoidàhuman
4th = multicotyledonaryàcow? (how to know)
Placental types by fetal/maternal separation
Placenta can also be classified by their invasiveness (i.e. how many tissue layers there are between fetal and maternal circulation)
Epitheliochorial = ruminant, mare, sow
Endotheliochorial = dog, cat
Hemochorial = rodents, humans. Have pool of maternal blood.
Placental types by fetal/maternal separation
Placenta can also be classified by their invasiveness (i.e. how many tissue layers there are between fetal and maternal circulation)
Epitheliochorial = ruminant, mare, sow
Endotheliochorial = dog, cat
Hemochorial = rodents, humans. Have pool of maternal blood.
Separation of circulation
In all placentae, fetal and maternal blood NEVER directly mix
Is not a problem when pregnant, but is at birth & lactation
If fetal blood gets into maternal circulation (e.g. placenta haemorrhage), it is treated as a foregin antigenàcan lead to sensitisation and downstream issues for offspring (e.g. neonatal isoerythrolysis)
Placentation - cattle
Placenta classification
- Cotyledonary (70-120, significantly increase
in size through gestation, have b.v.)
- Epitheliochorial
Unique features
- Convex caruncles on maternal epithelium
A definitive sign of pregnancy in rectal palpation! Placentome = fetal cotyledon + maternal caruncle
Placentation -
sheep
Placenta classification
sheep - Cotyledonary (90-100 cotyledons, significantly increase in size through gestation)
- Epitheliochorial
Unique features
- Concave caruncles (donut structure)
Placentation – Horse (mare)
Placenta classification
- Diffuse
- Epitheliochorial Unique features
- ‘F’ shaped placenta
- Microcotyledons (microscopic), evenly distributed
over surface
- Endometrial cups
o (placentalcellswhichinvadeinto
endometrium)
o 5-10transientstructures(d40-150)that
secrete eCG
o Note:eCGcausesaccessoryCL
- Cervical star
o Large,whiteavillousregionoverlyingcervix(noendometrialattachment),not
-
vascularied
Placentation - Pig
Placenta classification
- Diffuse
- Epitheliochorial
Unique features
- Simple chorionic villi
- Smooth surface
Placentation - dog
Placenta classification
- Zonary
- Endotheliochorial
Unique features
- Highly invasive villi in transfer zone
- Marginal band of haematoma
- Remainder of chorioallantois relatively
avascular
Placentation - cat
Placenta classification
- Zonary
- Endotheliochorial Unique features
- Highly invasive villi in transfer zone
- Relatively small marginal band of
haematoma
- Remainder of chorioallantois relatively
avascular
Scarring? Only zonary band attaches to uterine wall?
Placentas can be classified as epitheliochorial, endotheliochorial , haemochorial
Which species have an epitheliochorial planta? Equids, suids, ruminants
Histology of placenta
Chorionic trophoblast cells (AT) are typically cuboidal~columnar
Ruminants have both regular mononucleated and binucleated trophoblasts
- Invade endometrium
- Produce placental lactogen and PAGs
Why examine placenta?
Make sure whole placenta out uterus and none retained. If retained could get infection. Note: the blood supply on maternal side needs to turn off or mum bleeds to death. So need to get haemostasis (b.v. in uterus to contract and not haemorrhage). If placenta retained can interfere with this process (get haemorrhage).
