{{Short description|Narrow tube connecting the yolk sac and midgut lumen of a fetus}} {{Distinguish|urachus|allantois}} {{Infobox embryology | Name = Vitelline duct | Latin = ductus vitellinus | Image = Gray30.png | Caption = Fetus of about eight weeks, enclosed in the amnion. (Vitelline duct labeled at lower right.) | Image2 = Gray982.png | Caption2 = Sketches in profile of two stages in the development of the human digestive tube. (Vitelline duct labeled on bottom image.) | System = | CarnegieStage = | Days = 28 | Precursor = Midgut, yolk sac | GivesRiseTo = }} In the human embryo, the '''vitelline duct''', also known as the '''vitellointestinal duct''',<ref name="Dorlands">{{Citation |author=Elsevier |author-link=Elsevier |title=Dorland's Illustrated Medical Dictionary |publisher=Elsevier |url=http://dorlands.com/ |postscript=.}}</ref> the '''yolk stalk''',<ref name="Dorlands"/> the '''omphaloenteric duct''',<ref name="Dorlands"/> or the '''omphalomesenteric duct''',<ref name="Dorlands"/> is a long narrow tube that joins the yolk sac to the midgut lumen of the developing fetus.<ref name="usmle1_122">{{Cite book |last1 = Le |first1 = Tao |first2 = Vikas |last2 = Bhushan |first3 = Neil |last3 = Vasan |title = First Aid for the USMLE Step 1: 2010 20th Anniversary Edition |location = USA |publisher = The McGraw-Hill Companies, Inc. |year = 2010 |pages = [https://archive.org/details/firstaidforusmle0000unse_r6p4/page/122 122] |isbn = 978-0-07-163340-6 |url = https://archive.org/details/firstaidforusmle0000unse_r6p4/page/122 }} </ref> It appears at the end of the fourth week, when the yolk sac (also known as the umbilical vesicle) presents the appearance of a small pear-shaped 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 navel (umbilicus).<ref name="usmle1_122"/> 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 typically situated within two feet of the ileocecal junction and may be attached by a fibrous cord to the abdominal wall at the umbilicus.

===Persistence=== The yolk sac can be seen in the afterbirth as a small, somewhat oval-shaped body, the diameter of which varies from 1&nbsp;mm to 5&nbsp;mm. It is situated between the amnion and the chorion and may lie on the placenta or at a varying distance from it.

==Clinical significance== ===Meckel's diverticulum=== {{Main|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". In the decades since the mnemonic was developed, further epidemiology has found the incidence of symptomatic diverticulae to be 4%, not 2%,<ref>Robbins and Cotran, ''Pathologic Basis of Disease'', 8th ed., p. 766</ref><ref>Brant and Helms, ''Fundamentals of Diagnostic Radiology'', 4th ed., p. 778</ref> and the incidence to be 2–5x greater in males than females, but the mnemonic is still helpful.

==Additional images== <gallery> File:Gray983.png|Front view of two successive stages in the development of the digestive tube. </gallery>

==References== {{Reflist}}

==Further reading== *{{cite book |author=WebMD |chapter=omphalomesenteric duct |chapter-url=https://books.google.com/books?id=t8UfI3BH78wC&pg=PA305 |pages=305–6 |year=2009 |title=Webster's New World Medical Dictionary |edition=3rd |publisher=Houghton Mifflin Harcourt |isbn=978-0-544-18897-6}}

{{Extraembryonic and fetal membranes}} {{Authority control}}

{{DEFAULTSORT:Vitelline Duct}} Category:Embryology Category:Medical mnemonics