Wednesday 25 November 2009
In the human embryo, the vitelline duct, also known as the omphalomesenteric duct, is a long narrow tube that joins the yolk sac (vitelline sac) to the digestive tube. It appears at the end of the fourth week, when the yolk sac presents the appearance of a small pear-shaped vesicle (the umbilical vesicle).
The umbilical vesicle can be seen in the afterbirth 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 diverticulum, which is situated about two feet above the ileocecal junction, and may be attached by a fibrous cord to the abdominal wall at the umbilicus.
Sometimes a narrowing of the lumen of the ileum is seen opposite the site of attachment of the duct.
The omphalomesenteric duct normally becomes obliterated early in embryonic life but remnants may persist, producing an enteric fistula, an umbilical sinus, a subcutaneous cyst, or an umbilical polyp.
The umbilical polyp presents as a bright red polyp or fleshy nodule, 0.5–2 cm in diameter; it may discharge a mucoid secretion. A distinctive umbilical polyp, devoid of any epithelial component is termed a fibrous umbilical polyp.
omphalomesenteric duct remnant
- digestive development