yolk sac


Also found in: Thesaurus, Medical, Encyclopedia, Wikipedia.
Related to yolk sac: Gestational sac

yolk sac

n.
A membranous sac attached to the embryo and enclosing the yolk in egg-laying vertebrates. In humans and other placental mammals, it functions as the circulatory system for the embryo before internal circulation begins.

yolk sac

n
1. (Zoology) the membranous sac that is attached to the ventral surface of the embryos of birds, reptiles, and some fishes and contains yolk
2. (Zoology) the corresponding part in the embryo of mammals, which contains no yolk

yolk′ sac`


n.
an extraembryonic membrane that encloses the yolk of eggs.
[1860–65]

yolk sac

A sac attached to the gut of an embryo that encloses the yolk in bony fish, sharks, reptiles, mammals, and birds. In most mammals, the yolk sac functions as part of the embryo's circulatory system before the placenta develops.
ThesaurusAntonymsRelated WordsSynonymsLegend:
Noun1.yolk sac - membranous structure that functions as the circulatory system in mammalian embryos until the heart becomes functionalyolk sac - membranous structure that functions as the circulatory system in mammalian embryos until the heart becomes functional
sac - a structure resembling a bag in an animal
2.yolk sac - membranous structure enclosing the yolk of eggs in birds, reptiles, marsupials, and some fishes; circulates nutrients to the developing embryo
sac - a structure resembling a bag in an animal
References in periodicals archive ?
Taking the knife, she gently pierces the yolk sac and lets the yellow liquid pour into the steel bowl.
Pathology was consistent with a nasopharyngeal pure yolk sac tumor (YST).
The larvae were collected from eclosion until complete absorption of the yolk sac, at intervals of 2 to 6 hours; following this stage, larvae and juveniles were collected every 12 hours.
2007) reported that HPI axis is not efficient before the absorption of yolk sac in many fish species.
In the first three days of larvae development there was a gradual yolk sac reduction after which there was a switch to exogenous feeding.
MCNs may develop from endodermal immature stroma or primary yolk sac cells implanted during embryogenesis.
The team used the yolk sac - the first tissue where blood cells are made - from embryos that lacked Scl and within four hours of plating on the culture dish, the tissue had generated beating cardiomyocytes.
The yolk sac fluid was plated on selective MacConkey sorbitol agar.
1,2) The omphalomesenteric duct is the embryonic structure connecting the primary yolk sac to the embryonic midgut.
Unusual malignancies arising from BO include adenosquamous carcinoma, squamous cell carcinoma, sarcomatoid carcinoma, neuro-endocrine carcinoma, choriocarcinoma and yolk sac tumours.