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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 d ...
, 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 wikt:sac, 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' ...
to the midgut 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 Human fertilization is the union of a human egg and sperm, occurring primarily in the ampulla of the fallopian tube. The result of this union leads to the production of a fertilized egg called a zygote, initiating embryonic development. Scient ...
(9th week of gestational age), but a failure of the duct to close is termed a vitelline fistula. This results in discharge of
meconium Meconium is the earliest stool of a mammalian infant resulting from defecation. Unlike later feces, meconium is composed of materials ingested during the time the infant spends in the uterus: intestinal epithelial cells, lanugo, mucus, amnioti ...
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 In medicine or biology, a diverticulum is an outpouching of a hollow (or a fluid-filled) structure in the body. Depending upon which layers of the structure are involved, diverticula are described as being either true or false. In medicine, t ...
protruding from the
small intestine The small intestine or small bowel is an organ (anatomy), organ in the human gastrointestinal tract, gastrointestinal tract where most of the #Absorption, absorption of nutrients from food takes place. It lies between the stomach and large intes ...
, 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 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 The amnion is a membrane that closely covers the human and various other embryos when first formed. It fills with amniotic fluid, which causes the amnion to expand and become the amniotic sac that provides a protective environment for the develo ...
and the chorion 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 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 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.


References


Further reading

* {{DEFAULTSORT:Vitelline Duct Embryology Medical mnemonics