The
placenta
The placenta (: placentas or placentae) is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas, and waste exchange between ...
of humans, and certain other mammals contains structures known as cotyledons, which transmit fetal blood and allow exchange of oxygen and nutrients with the maternal blood.
Ruminants
The
Artiodactyla
Artiodactyls are placental mammals belonging to the order (biology), order Artiodactyla ( , ). Typically, they are ungulates which bear weight equally on two (an even number) of their five toes (the third and fourth, often in the form of a hoof ...
have a cotyledonary placenta. In this form of placenta, the chorionic villi form a number of separate circular structures (''cotyledons'') which are distributed over the surface of the chorionic sac. Sheep, goats and cattle have between 72 and 125 cotyledons whereas deer have 4-6 larger cotyledons.
Human
The form of the human placenta is generally classified as a discoid placenta. Within this, the ''cotyledons'' are the approximately 15-25 separations of the
decidua basalis
The decidua is the modified mucosal lining of the uterus (that is, modified endometrium) that forms every month, in preparation for pregnancy. It is shed off each month when there is no fertilized egg to support. The decidua is under the influe ...
of the placenta, separated by placental
septa
SEPTA, the Southeastern Pennsylvania Transportation Authority, is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly four million people througho ...
.
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/ref> Each cotyledon consists of a main stem of a chorionic villus
Chorionic villi are villi that sprout from the chorion to provide maximal contact area with maternal blood.
They are an essential element in pregnancy from a histomorphologic perspective, and are, by definition, a product of conception. Branch ...
as well as its branches and sub-branches.[
]
Vasculature
The cotyledons receive fetal blood from chorionic vessels
Chorionic (plate) vessels, also fetal surface vessels are blood vessels, including both arteries and veins, that carry blood through the chorion in the placenta#Fetoplacental circulation, fetoplacental circulation.
Chorionic arteries branch off t ...
, which branch off ''cotyledon vessels'' into the cotyledons, which, in turn, branch into capillaries.
References
External links
Diagram (page in French)
Vertebrate developmental biology
Embryology
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