Umbilical Cord Differences
How are umbilical cords differennt between mammals and birds?
Avians (birds), lay eggs, so there is no umbilical cord between the mother
and the offspring.
Bird embryos are placed inside a shell before being laid, and therefore do
not have umbilical cords.
The umbiical cord of mammals provide the nutrient and waste exchange between
the growing embryo and the mother. Birds lay eggs which contain a nutrient
yolk sac and the allantois that stores wastes and allows for improved gas
exchange. There is no umbilical cord. It is interesting to note that in
early mammal development, the yolk sac and allantois is present, but do not
function as they do with birds. Evolutionary connection here.
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Update: June 2012