Placentation Flashcards
Prototherian
egg laying
platypus, echidnas
first beasts
Metatherian
changed beasts
choriovitelline placenta- aka yolk sac
marsupials- kangaroos, koala, opossum
develop within pouch
Eutherian
true beasts
chorioallantoic placenta and the rest
Placenta
vascular organ formed in uterus during pregnancy
consisting of both maternal and embryonic/fetal tissues and providing O2 and nutrients for the fetus and transfer of waste products from fetal to maternal blood circulation
Placenta structure
chorioallantoic on fetal side connected to endometrium on maternal side
fetal membranes
membranes that function for the protection or nourishment or respiration or excretion of developing fetus
yolk sac, then amnion, then allantois (large) and chorion
time comparisons from ovulation during cleavage for different farm species
enter uterus on different days
cattle= 3-5
horse= 5
sheep=3
swine= 2
development of allantochorion
start with inner cell mass within blastocoel
the ICM forms an embryo and enters blastocoel
yolk sac forms which is the 1st fetal membrane, for early nourishment
mesoderm begins to fold and amnionic folds begin to surround the embryo
primitive gut below embryo and yolk sac shrinks as allantois begins to expand
mesoderm and trophectoderm together form chorion
allantois expands getting larger and an amnionic cavity surrounds the embryo
attachment of the placenta to the uterus
implantation
cow= day 30-35 sow= 12-20 ewe= 18-20 mare= 50-60
roles of the placenta
nutrient exchange gas exchange stores waste protective endocrine organ
fetal membranes
yolk sac, amnion, allantois and chorion
Yolk sac
early nutrition for the embryo (usually regresses completely)
Amnion
transparent membrane surrounding the fetus, protects fetus from injury, provides lubrication for parturition, reservoir for urine and wastes
protection (cushion), waste, and nutrient exchange
Allantois
blood supply for chorion
waste
fuses with chorion and carries blood vessels of placenta, reservoir for nutrients and wastes, umbilical cord attaches fetus to allantois
Chorion
maternal interface
nutrient and gas exchange
attaches to uterus, absorbs nutrients from uterus, allows maternal/fetal gas exchange, produces hormones
placenta makeup
endometrium + chorion and allantois
placenta classification
distribution of contact areas- shape
tissue layers separating maternal and fetal blood- invasion
degree of interdigitation of the vasculature
maternal tissue loss at birth
4 distributions of contact areas
diffuse, cotyledonary, zonary, discoid
diffuse
villi everywhere
horse and pig
cotyledonary
rows and very specific numbers
ewe and cow
placentome
caruncle + cotyledon
caruncle on maternal side, interacts with cotyledon which is on fetal side
zonary
single (band aid appearance)- dog and cat
double (band aid appearance)- ferret and raccoon
discoid
monkey, man and rodent
layers separating maternal and fetal circulation
6 layers
fetal layers= endothelium, connective tissue and epithelium
maternal layers= epithelium, connective tissue, endothelium
maternal and fetal blood will not mix, don’t erode enough
Five layer separation
same as 6 but one less layer on the maternal side
no epithelium
Four layer separation
same as 5 layer separation but no connective tissue
Three layer separation
Only fetal side with maternal layer similar to deciduate
Epitheliochorial
5-6 layers
synepitheliochorial (transiently 5 layers) - ruminant placenta, mostly bovine, partial erosion
horse, pig, cattle, sheep and goats
starts at maternal endometrial capillary and travels to chorionic capillary
ruminants= both partial and transient erosions of endometrium
Endotheliochorial
4-5 layers
carnivores, from endometrial capillary to chorionic capillary
Hemochorial
3 layers (only on fetal side)
maternal blood pool goes to fetus
primates and rodents
Ruminant species epitheliochorial
binucleate cells- chorionic origin, fuse with maternal epithlium= syncytium, placental lactogen, and specific proteins
Binucleate giant cells migrate into maternal side as grow and then enter maternal circulation
Pig interdigitation
folded type
Horse interdigitation
lamellar type
human interdigitation
trabecular type
cattle interdigitation
villous type
dog interdigitation
labyrinthine type
maternal tissue lost at birth
non-deciduate/adeciduate (non invasive)
deciduate (endometrial loss)
non-deciduate/adeciduate
complete separation of maternal and fetal tissues
sow, mare ruminant
in mare= micro cotyledons and in sow= chorionic villi
deciduate placenta
loss of maternal tissue at parturition
carnivores, humans and rodents
diffuse placenta: sow
necrotic tips of the placenta
folded with areolae (chorionic villi)
diffuse, epitheliochorial, adeciduate placenta
diffuse placenta mare
microcotyledons= villi in clumps
diffuse, epitheliochorial, adeciduate placenta
twins in horses
not enough placental attachment to survive
ruminant species
cotyledonary, epitheliochorial, adeciduate placenta
amnion around fetus
placentomes and chorioallantois
convex cotyledons
cow and giraffe
caruncular tissue intermingles with chorionic tissue
concave cotyledons
sheep and goat
chorionic tissue deeper within caruncular tissue
membrane slip
2 layers and can feel separation
carnivore species placenta
zonary, endotheliochorial, and deciduate placenta
pigmented zone around TZ (bandaid appearance)
on maternal side- marginal hematomas (source of iron)
hematophagous zone= phagocytosis of RBC by chorionic epithelium
heme converted to green biliverdin (pigment) = seen on edge of chorion and allantois
placenta in the cat
larger zonary placenta around amnion
primate placenta
discoid, hemochorial, deciduate placenta
