In the

human embryo Human embryonic development, or human embryogenesis, is the development and formation of the human embryo. It is characterised by the processes of cell division and cellular differentiation of the embryo that occurs during the early stages of ...

, the vitelline duct, also known as the vitellointestinal duct, the yolk stalk, the omphaloenteric duct, or the omphalomesenteric duct, is a long narrow tube that joins the

yolk sac The yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac'' is ...

to the

midgut The midgut is the portion of the embryo from which most of the intestines develop. After it bends around the superior mesenteric artery, it is called the "midgut loop". It comprises the portion of the alimentary canal from the end of the foregut a ...

lumen of the developing

fetus A fetus or foetus (; plural fetuses, feti, foetuses, or foeti) is the unborn offspring that develops from an animal embryo. Following embryonic development the fetal stage of development takes place. In human prenatal development, fetal dev ...

. It appears at the end of the fourth week, when the yolk sac presents the appearance of a small pear-shaped

vesicle Vesicle may refer to: ; In cellular biology or chemistry * Vesicle (biology and chemistry) In cell biology, a vesicle is a structure within or outside a cell, consisting of liquid or cytoplasm enclosed by a lipid bilayer. Vesicles form nat ...

(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 In obstetrics, gestational age is a measure of the age of a pregnancy which is taken from the beginning of the woman's last menstrual period (LMP), or the corresponding age of the gestation as estimated by a more accurate method if available. Su ...

), but a failure of the duct to close is termed a vitelline fistula. This results in discharge of meconium from the umbilicus. 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 A Meckel's diverticulum, a true congenital diverticulum, is a slight bulge in the small intestine present at birth and a vestigial remnant of the omphalomesenteric duct (also called the vitelline duct or yolk stalk). It is the most common malformat ...

, which is typically situated within two feet of the

ileocecal junction The ileocecal valve (ileal papilla, ileocaecal valve, Tulp's valve, Tulpius valve, Bauhin's valve, ileocecal eminence, valve of Varolius or colic valve) is a sphincter muscle valve that separates the small intestine and the large intestine. Its ...

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 The chorion is the outermost fetal membrane around the embryo in mammals, birds and reptiles (amniotes). It develops from an outer fold on the surface of the yolk sac, which lies outside the zona pellucida (in mammals), known as the vitell ...

and may lie on or at a varying distance from the

placenta The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mate ...

Clinical significance

Meckel's diverticulum

Sometimes a narrowing of the lumen of the

ileum The ileum () is the final section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear and the terms posterior intestine or distal intestine m ...

is seen opposite the site of attachment of the duct. On this site of attachment, sometimes a pathological

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 The ileocecal valve (ileal papilla, ileocaecal valve, Tulp's valve, Tulpius valve, Bauhin's valve, ileocecal eminence, valve of Varolius or colic valve) is a sphincter muscle valve that separates the small intestine and the large intestine. Its ...

, 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%,Brant and Helms, ''Fundamentals of Diagnostic Radiology'', 4th ed., p. 778 and the incidence to be 2–5x greater in males than females, but the mnemonic is still helpful.

Additional images

File:Gray983.png, Front view of two successive stages in the development of the digestive tube.