出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/09/14 21:16:19」(JST)
| Vitelline duct | |
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Fetus of about eight weeks, enclosed in the amnion. (Vitelline duct labeled at lower right.)
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Sketches in profile of two stages in the development of the human digestive tube. (Vitelline duct labeled on bottom image.)
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| Details | |
| Days | 28 |
| Precursor | midgut, yolk sac |
| Identifiers | |
| Latin | ductus vitellinus |
| MeSH | A16.254.891 |
| Anatomical terminology
[edit on Wikidata]
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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).
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.
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.
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] Other references indicate that a Meckel diverticulum may be seen within 2 feet of the ileocecal valve.[3]
Front view of two successive stages in the development of the digestive tube.
Membranes of the fetus and embryo
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| Embryo |
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| Circulatory |
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| リンク元 | 「卵黄腸管」 |
| 関連記事 | 「duct」「ductus」 |