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. SYN: umbilical vesicle, vesicula umbilicalis, vitelline sac.
Source: Stedman's Medical Spellchecker, © 2006 Lippincott Williams & Wilkins. All rights reserved.
Yolk sac: sometimes called vitelline sac; do not confuse with vitelline membrane of the egg; an embryonic membrane formed from endoderm and mesoderm; in reptiles and birds it incorporates the yolk into the digestive tract for nourishing the embryo; in placental mammals it is the source of most of the intestinal mucosa and the site of formation of the germ cells.
Source: CRISP
Yolk sac: The first of four extra-embryonic membranes to form during EMBRYOGENESIS. In REPTILES and BIRDS, it arises from endoderm and mesoderm to incorporate the EGG YOLK into the DIGESTIVE TRACT for nourishing the EMBRYO. In placental MAMMALS, its nutritional function is vestigial; however, it is the source of INTESTINAL MUCOSA; BLOOD CELLS; and GERM CELLS. It is sometimes called the vitelline sac, which should not be confused with the VITELLINE MEMBRANE of the egg.
Source: MeSH 2007
These medical condition or symptom topics may be relevant to medical information for Yolk sac:
Source - MeSH 2007
Source - CRISP
Source: CRISP
The following list attempts to classify Yolk sac into categories where each line is subset of the next.
Search to find out more about Yolk sac:
|
What do you think about the features of this website? Take our user survey and have your say:
Tools & Services:
Medical Articles:
Search Specialists by State and City
By using this site you agree to our Terms of Use. Information provided on this site is for informational purposes only; it is not intended as a substitute for advice from your own medical team. The information on this site is not to be used for diagnosing or treating any health concerns you may have - please contact your physician or health care professional for all your medical needs. Please see our Terms of Use.
Copyright © 2009 Health Grades Inc. All rights reserved.
