yolk stalk

n. (Medicine) narrow tube that connects the yolk sac with the midgut of the embryo

At the end of the fourth week the yolk-sac presents the appearance of a small pear-shaped vesicle (umbilical vesicle) opening into the digestive tube by a long narrow tube, the vitelline duct.The vesicle can be seen in the after-birth as a small, somewhat oval-shaped body whose diameter varies from 1 mm. to 5 mm.; it is situated between the amnion and the chorion and may lie on or at a varying distance from the placenta. As a rule the duct undergoes complete obliteration during the seventh week, but in about two per cent of cases its proximal part persists as a diverticulum from the small intestine, Meckel's diverticulum, which is situated about two feet above the ileocolic junction, and may be attached by a fibrous cord to the abdominal wall at the umbilicus.
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A narrow tube present in the early embryo that connects the midgut of the embryo (through the umbilical opening) to the yolk sac outside the embryo. Later in development, the yolk stalk is usually obliterated but a remnants of it may persist, most commonly as a finger-like protrusion from the small intestine known as Meckel’s diverticulum. Found in 2-4% of people, Meckel’s diverticulum may become inflamed much like the appendix and require surgical removal. The yolk stalk is also called the umbilical duct, vitelline duct, or oomphalomesenteric duct.