The small sac connected to a newborn salmon during the alevin stage of a salmon's development, which provides the tiny fish with protein, sugar, minerals, and vitamins.
One of four extraembryonic membranes that supports embryonic development; the first site of blood cells and circulatory system function.
A small sac connected to alevin which provides them with protein, sugar, minerals, and vitamins. Alevin live on this "lunch bag" for a month or so before emerging from the gravel and beginning to hunt food for themselves.
a vascularized extra-embryonic membrane of amniote embryos that forms around the yolk of the egg cell in birds and reptiles. In mammals, the yolk sac membrane grows out around the empty blastocoel (blastula cavity) formed within the inner cell mass in the cleaving embryo. The blastocoel is renamed the yolk sac. In birds and reptiles, the blood vessels in its walls transport yolk nutrients to the embryo. In mammals, these vessels still form even though they don't supply nutrients to the embryo. They remain to form blood vessels in the digestive tract
A sac-like structure attached to the under-surface of the developing embryo. The first part of the embryo to become visible on transvaginal ultrasound after the gestational sac, but not by itself as reassuring as seeing a beating fetal heart that the pregnancy will most likely avoid miscarriage. Not as important for a human embryo's nutrition as it is for a fertilised egg incubated by a hen, and in mammals contains no yolk, but the yolk sac's lumen is continuous with the lumen of the embryo's developing gut, or intestine, and shares an absorptive function. Cells from the yolk sac become incorporated into the fetus in many ways, including forming the primitive germ cells.
Food supply in a cleidoic egg.
One of the protective membranes surrounding the embryo
membranous structure that functions as the circulatory system in mammal embryos until the heart becomes functional
membranous structure enclosing the yolk of eggs in birds reptiles marsupials and some fishes; circulates nutrients to the developing embryo
where the embryo develops
A small circular sac containing nutrients for the developing embryo; the first sign of developing pregnancy seen by ultrasound.
An external pouch containing nutrients for the growing alevin. When the yolk sac is used up, the alevin is said to be "buttoned-up" and enters the fry stage.
Part of the embryo during development which may rarely lead to cancerous growth in the gonads, sacrum and in the chest cavity
The yolk sac in man contains no nutrients so in this aspect is vestigial. However, the its embryonic endodermal roof is the source of the mucous membrane of almost the entire intestinal tract. The yolk sac also is concerned with the transfer of nutritive fluid to the embryo from the trophoblast, primary mesenchyme and extra-embryonic coelem.
the membrane-covered food pouch found on the belly of a newly hatched fish. It nourishes the growing fish until it is able to feed itself.
A small container still connected to the baby fish after hatching, consisting of the unabsorbed egg yolk.
An extraembryonic membrane enclosing and absorbing the yolk of amniote embryos. It is formed from a layer of endoderm and a layer of splanchnic mesoderm (splanchnopleure).
a membrane-bound compartment in the amniotic egg which contains stored food for the developing embryo.
The yolk sac is the first element seen in the gestational sac during pregnancy, usually at 5 weeks gestation.
