umbilical vesicle

vesicle

[ves´ĭ-k'l] 1. a small bladder or sac containing liquid.2. a small circumscribed elevation of the epidermis containing a serous fluid; a small blister.allantoic vesicle the internal hollow portion of the allantois.auditory vesicle a detached ovoid sac formed by closure of the auditory pit in the early embryo, from which the percipient parts of the inner ear develop.brain v's the five divisions of the closed neural tube in the developing embryo, including the telencephalon, diencephalon, mesencephalon, metencephalon, and myelencephalon.brain v's, primary the three earlier subdivisions of the embryonic neural tube, including the forebrain, midbrain, and hindbrain.brain v's, secondary the four brain vesicles formed by specialization of the forebrain and of the hindbrain in later embryonic development.chorionic vesicle the chorion of a mammal.encephalic v's brain vesicles.germinal vesicle the fluid-filled nucleus of an oocyte toward the end of prophase of its meiotic division.lens vesicle a vesicle formed from the lens pit of the embryo, developing into the crystalline lens.olfactory vesicle 1. the vesicle in the embryo that later develops into the olfactory bulb and tract.2. a bulbous expansion at the distal end of an olfactory cell, from which the olfactory hairs project.optic vesicle an evagination on either side of the forebrain of the early embryo, from which the percipient parts of the eye develop.otic vesicle auditory vesicle.seminal vesicle paired sacculated pouches attached to the posterior urinary bladder; the duct of each joins the ipsilateral ductus deferens to form the ejaculatory duct.umbilical vesicle the pear-shaped expansion of the yolk sac growing out into the cavity of the chorion, joined to the midgut by the yolk stalk.

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. Synonym(s): umbilical vesicle, vesicula umbilicalis, vitelline sac