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yolk
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yolk Amniotic egg. structural components of an egg
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yolk
yolk The yolk of a chicken egg.

yolk

embryology
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Also known as: deutoplasm, egg yolk
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Also called:
Deutoplasm

yolk, the nutritive material of an egg, used as food by a developing, embryonic animal. Eggs with relatively little, uniformly distributed yolk are termed isolecithal. This condition occurs in invertebrates and in all but the lowest mammals. Eggs with abundant yolk concentrated in one hemisphere of the egg are termed telolecithal. This occurs in many invertebrates and in all vertebrates lower than marsupial mammals. In arthropods, the yolk is massed near the centre of the egg; such eggs are termed centrolecithal.

This article was most recently revised and updated by Amy Tikkanen.