The
placenta
The placenta 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 the physically separate mater ...
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
The even-toed ungulates (Artiodactyla , ) are ungulates—hoofed animals—which bear weight equally on two (an even number) of their five toes: the third and fourth. The other three toes are either present, absent, vestigial, or pointing poster ...
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 fertilised egg to support. The decidua is under the influen ...
of the placenta, separated by placental
septa
The Southeastern Pennsylvania Transportation Authority (SEPTA) is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly 4 million people in five coun ...
.
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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. Branche ...
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 fetoplacental circulation.
Chorionic arteries branch off the umbilical artery, and supply the ...
, 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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