yolk (yōk) the stored nutrient of an oocyte or ovum.
yolk
yolk (y k)n. The portion of the egg of an animal that consists of protein and fat from which the early embryo gets its main nourishment and of protoplasmic substances from which the embryo develops. |
yolk
[yōk, yelk]
Etymology: AS, geolca
a material rich in fats and proteins that is contained in an ovum and that supplies nourishment to the developing embryo. The amount and distribution of the yolk within the ovum depend on the species of animal and the type of reproduction and development of offspring. In humans and most other mammals, yolk is absent or greatly diffused through the ovum. Mammalian embryos absorb nutrients directly from the mother through the placenta. Also called vitellus. See also deutoplasm.
yolk
1. the stored nutrient of the ovum; it is also rich in antibody which is absorbed into the circulation of the embryo in the last third of incubation and is the mechanism by which maternal antibody is transferred to the young bird. See also yolk sac, egg.
2. the combined secretion of the sebaceous and sudoriferous glands of the sheep's skin and extractable from the fleece.
yolk sacculitis
see avian omphalitis.
yolk stalk
the connection, passing through the umbilicus, between the yolk sac and the fetus.
yolk stain
a stain of wool originating from the yolk.
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