yolk sac


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Related to yolk sac: Gestational sac

sac

 [sak]
a baglike organ or structure; see also bag, pocket, and pouch.
air s's (alveolar s's) the spaces into which the alveolar ducts open distally, and with which the alveoli communicate; see also lung.
amniotic sac the sac formed by the amnion, enclosing the fetus suspended in amniotic fluid; popularly known as the bag of waters.
conjunctival sac the potential space, lined by conjunctiva, between the eyelids and the eyeball.
endolymphatic sac the blind, flattened cerebral end of the endolymphatic duct.
hernial sac the peritoneal pouch that encloses protruding intestine.
lacrimal sac the dilated upper end of the nasolacrimal duct; see also lacrimal apparatus.
yolk sac the extraembryonic membrane connected with the midgut; in vertebrates below true mammals, it contains a yolk mass.
Yolk sac in a developing embryo. From Applegate, 2000.

yolk sac

1. in vertebrates with telolecithal eggs, the highly vascular layer of splanchnopleure surrounding the yolk of an embryo;
2. in humans and other mammals, the sac of extraembryonic membrane that is located ventral to the embryonic disk and, after formation of the gut tube, is connected to the midgut; by the second month of development, this connection has become the narrow yolk stalk; the yolk sac is the first hematopoietic organ of the embryo, and its vitelline circulation plays an important role in the early embryonic circulation; the sac is also the site of origin of the primordial germ cells.

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.

um·bil·i·cal ves·i·cle

(ŭm-bil'i-kăl ves'i-kĕl)
A saclike structure formed from the exocelomic cavity of a blastocyst.
Synonym(s): yolk sac.

yolk sac

A tiny bag attached to the embryo that provides early nourishment before the PLACENTA is formed.

yolk sac

the sac-like structure that contains YOLK and is in direct contact with the gut of embryos in fish, reptiles and birds. Though present in mammalian embryos, it does not contain yolk but absorbs uterine secretions until the PLACENTA (1) becomes functional.
References in periodicals archive ?
rotundiformis; the brine shrimp Artemia at several life stages (i.e., nauplii, juveniles and adults); copepods Pseudodiaptomus euryhalinus at several life stages (nauplii, copepodites and adults); wild zooplankton; and even yolk sac larvae from the same species.
On the basis of examination of a small number of reproductive tracts, velvet dogfish have been described as aplacental viviparous sharks that fit the type-II yolk-sac reproductive mode (in which several embryos with attached yolk sacs are contained in utero without uterine compartments) (Otake, 1990).
Reports state hepatoid carcinoma as the representative type along with GCED, tubular adenocarcinoma, papillary adenocarcinoma, poorly differentiated adenocarcinoma, and yolk sac tumor [1-9].
The yolk sac is important because it transfers passive immunity from the yolk to the newly hatched chick in the form of immunoglobulins, however, it must have at its disposal adequate sources of exogenous nutrients.
Only 33.3% cases of Yolk sac tumour gave positive results with AFP.
The yolk sac tissue develops on the third day of pregnancy but usually dissolves within a month.
The most specific sonographic finding of an ectopic pregnancy is an extrauterine gestational sac with a yolk sac or embryo (Figure l).
A volume of 50ul containing 0.3ul of RA (Sigma) in saline was administered via yolk sac to the group A on day 0 of incubation16.
* Double-bleb bulgusu: Bazen korion icerisinde amniotik kese ile yolk sac'a ait iki ayri kese ve arasinda sandvic seklinde embrio izlenebilir.
As of now, researchers say these embryos are "unlikely to develop into a healthy foetus as it would probably need the third form of stem cell [the primitive endoderm], which develops into the yolk sac that provides nutrition," the BBC reported.