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Vitelline duct

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Vitelline duct

Vitelline duct
Fetus of about eight weeks, enclosed in the amnion. (Vitelline duct labeled at lower right.)
Sketches in profile of two stages in the development of the human digestive tube. (Vitelline duct labeled on bottom image.)
Details
Latin ductus vitellinus
Days 28
midgut, yolk sac
Identifiers
Gray's p.54
MeSH A16.254.891
Anatomical terminology

In the human embryo, the vitelline duct, also known as the omphalomesenteric duct, is a long narrow tube that joins the yolk sac to the midgut lumen of the developing fetus.[1] 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).

Function

Obliteration

Generally, the duct fully obliterates (narrows and disappears) during the 5–6th week of fertilization age (9th week of gestational age), but a failure of the duct to close is termed a vitelline fistula. This results in discharge of meconium from the umbilicus.[1] About two percent of fetuses exhibit a type of vitelline fistula characterized by persistence of the proximal part of the vitelline duct as a diverticulum protruding from the small intestine, Meckel's 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.

Persistence

The vesicle can be seen in the afterbirth as a small, somewhat oval-shaped body, the diameter of which 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.

Clinical significance

Meckel's Diverticulum

Sometimes a narrowing of the lumen of the ileum is seen opposite the site of attachment of the duct. On this site of attachment, sometimes a pathological Meckel's diverticulum may be present.

A mnemonic used to recall details of a Meckel's diverticulum is as follows: "2 inches long, within 2 feet of ileocecal valve, 2 times as common in males than females, 2% of population, 2% symptomatic, 2 types of ectopic tissue: gastric and pancreatic". Note that the true number of symptomatic diverticulae is 4%.[2]

Additional images

References

  1. ^ a b Le, Tao; Bhushan, Vikas; Vasan, Neil (2010). First Aid for the USMLE Step 1: 2010 20th Anniversary Edition. USA:  
  2. ^ Robbins and Cotran, Pathologic Basis of Disease, 8th ed., p. 766

External links

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