Placentation, Placental Development, Placental Function and Foetal Growth

Placentation, Placental Development, Placental Function and Foetal Growth
 There are different shapes of placenta that are found in different species
o Discoid (a)- human and rodent
 Interaction is confined to one disc shaped area
o Zonary (b)- cat and dog
 Interdigitation of membranes forming belt around chorionic sac
o Cotyledonary (c)- cow and sheep
 Each little blob forms a different placenta
o Diffuse (d)- horse
 Whole surface of the maternal membrane is the placenta
 Highly vascularised with many folds




o
 Sheep uterus- can be hyperstimulated to make more blastocysts
o Sheep have cotyledonary uterus
o Non pregnant sheep uterus
 Can see the corpora lutea in the ovaries




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 Caruncles are the implantation sites, around 80 in sheep uterus
 If one of the caruncles is removed, others compensate for it

, 
o Caruncles are found on the maternal side
o Cotyledons are found on the foetal side
o Placentome- individual placental unit, a combination of a caruncle and a
cotyledon
 Placentation creates a vascular supply to supply the foetus with blood
 Interdigitation of foetal material and maternal material in the
caruncle
 Trophoblast dips into the caruncles
 Maternal side is formed of a capillary bed
 Surrounded by epithelia
 Comes in in uterine artery, leaves through the uterine vein
 Specially adapted to match foetal capillary bed




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o In sheep there are a layer of endothelial cells, and then epithelial cells on the
maternal side
 On the foetal side there an endothelial and trophoblast layer
 Blood has to cross 4 layers from mother to embryo
 Different types of placentation can also be described by their histological features