yolk sac


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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.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

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
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014

yolk′ sac`


n.
an extraembryonic membrane that encloses the yolk of eggs.
[1860–65]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.

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.
The American Heritage® Student Science Dictionary, Second Edition. Copyright © 2014 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
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
Based on WordNet 3.0, Farlex clipart collection. © 2003-2012 Princeton University, Farlex Inc.
References in periodicals archive ?
Rather, there's tissue called the "fetal pole"--a thickening of the yolk sac that holds an embryo at six weeks--that exhibits some cardiac activity.
Average total length is 1.50 [+ or -] 0.10 mm, and a single oil globule (diameter of 0.13 [+ or -] 0.06 mm) is present in the anterior portion of the yolk sac (Butler et al., 1982).
The histotypes include seminoma, embryonal carcinoma, yolk sac tumor, trophoblastic tumors, teratoma, mixed germ cell tumor, and regressed germ cell tumor.
Chicks selected for high growth rates depend on exogenous, extra-yolk-sac feeding very soon after hatching because nutrient supply via yolk sac is not sufcient to sustain the extreme growth of chick after hatching and absence of feed in the gut in very early post-hatching period impairs development, hence, late collection and placement at farm from the hatchers probably after twelve hours may result in the loss of body weight (BW) of 2.6% and 2.3% for males and females respectively (Gonzales et al., 2003).
The other two types of stem cell in the blastocyst are the extra-embryonic trophoblast stem cells (TSCs), which will form the placenta, and primitive endoderm stem cells (PESCs) that will form the yolk sac, ensuring that the fetus's organs develop properly and providing essential nutrients.
Effect of salinity on three tilapia (Oreochromis sp.) strains: hatching rate, length and yolk sac size.
The reproductive classification that we used for mature females had 7 stages: 1) developing ova, nongravid, with developing ovarian ova and expanded uteri (>10 mm); 2) large ova nongravid, with ova and expanded uteri (>10 mm); 3) ovulating, with eggs in body cavity; 4) uterine ova, ova in the uteri after ovulation; 5) developing embryos, obvious embryos with yolk sacs in the uteri; 6) near-term embryos, uterine embryos that have absorbed their external yolk sac; and 7) postpartum stage: no uterine embryos and large flaccid uteri (>20 mm).
After completing eight cycles of chemotherapy for ovarian yolk sac tumor, Fatima Ivy Rodriguez is again undergoing treatment for another tumor growth.
It is important that supplemental feeders should not run empty as this will cause stress on the chicks and reduce yolk sac re-absorption.Refresh feeders with new feed three times a day to increase appetite.