The gastrointestinal tract (GIT) extending from the buccopharyngeal membrane to the cloacal membrane arises from the endoderm of the trilaminar embryo (week 2, 3).
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Foregut behind the develping heart |
Cartoon of GIT cross-section and peritoneal cavity |
Herniation of the midgut |
During the 4th week the 3 distinct portions (fore-, mid- and hind-gut) extend the length of the embryo and will contribute different components of the GIT. The large mid-gut is generated by lateral embryonic folding which "pinches off" a pocket of the yolk sac, the 2 compartments continue to communicate through the vitelline duct. On this current page there is a brief developmental overview and stage 13/14 embryo overview.
The oral cavity (mouth) is formed following breakdown of the buccopharyngeal membrane (=oropharyngeal) and contributed to mainly by the pharynx lying within the pharyngeal arches. The opening of the GIT means that it contains amniotic fluid, which is also swallowed later in development. (More? Sensory Development - Taste | Head and Neck Development - Tongue)
From the oral cavity the next portion of the foregut is initially a single gastrointestinal (oesophagus) and respiratory (trachea) common tube, the pharynx which lies behind the heart. Note that the respiratory tract will form from a ventral bud arising at this level (More? Respiratory Development)
The walls of this tube will proliferate, become solid, then recanulise to form the definitive gut. Failure to recanalise correctly can generate abnormalities (More? GIT Movies | GIT Abnormalities) |
There is also a detailed summary of components that contribute to formation of the GIT.
Page Links: Introduction | Reading | Objectives | Computer Activities | stage 13/14 embryo | stage 22 embryo | stage 22 embryo highpower | Development Timing | Development Overview | References | Glossary
Related Pages: Abnormalities | Stage 13/14 | Stage 22 | Selected stage 22 | Histology | Overview | Liver | Gall Bladder | Spleen | Pancreas | Stomach | GIT Folding | Intestine | Molecular | Tongue | Taste | Postnatal | Milk | GIT WWW LinksSangiorgi E, Capecchi MR. Bmi1 is expressed in vivo in intestinal stem cells. Nat Genet. 2008 Jul;40(7):915-20.
"We found that Bmi1 is expressed in discrete cells located near the bottom of crypts in the small intestine, predominantly four cells above the base of the crypt (+4 position). ... Unexpectedly, the distribution of Bmi1-expressing stem cells along the length of the small intestine suggested that mammals use more than one molecularly distinguishable adult stem cell subpopulation to maintain organ homeostasis."
Natasza A. Kurpios, Marta Ibañes, Nicole M. Davis, Wei Lui, Tamar Katz, James F. Martin, Juan Carlos Izpisúa Belmonte, and Clifford J. Tabin. The direction of gut looping is established by changes in the extracellular matrix and in cell:cell adhesion PNAS 2008 105: 8499-8506; published online on June 23, 2008
"The counterclockwise coiling of the intestines is initiated by a leftward tilt of the primitive gut tube, imparted by left–right asymmetries in the architecture of the dorsal mesentery. ...We find that the dorsal mesentery extracellular matrix is indeed left–right asymmetric and moreover that the adhesion molecule N-cadherin is expressed exclusively on the left side."
(More? GIT References)
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Foregut - beneath the transverse septum the tract grows rapildy, dilating and rotaing to form the primitive stomach. Growth and rotation generates curvatures, peritoneal sacs and a large attached omentum (More? Stomach Development). The hepatic diverticulum (liver bud) lies under the septum transversum and is the earliest associated GIT organ that has differentiated, and will occupy a substantial region of the abdomen during development. (More? Liver Development)
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Midgut - beneath the stomach the initial portion of the small intestine, the duodenum, and the associated pancreas now lie. Much of the midgut is herniated at the umbilicus external to the abdomen through development. A key step in development is the rotation of this midgut that must occur to place the GIT in the correct abdominal position with its associated mesentry. The GIT itself differentiates to form significantly different structures along its length: oesophagus, stomach, duodenum, jejunum, iliem (small intestine), colon (large intestine). (More? Intestine Development) The mesentries of the GIT are generated from the common dorsal mesentry, with the ventral mesentry contributing to the lesser omentum and falciform ligament.
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The pancreas arises from 2 sources: the hepatic diverticulum (ventral) and the duodenum (dorsal). The pancreas must also differentiate to establish specific cells for endocrine and exocrine function. (More? Pancreas Development)
The spleen arises in week 5 within the dorsal mesogastrium as proliferating mesenchyme. Cells required for its hemopoietic function arise from the yolk sac wall and near dorsal aorta. The spleen generates both red and white cells in the 2nd trimester. Note that many embryonic RBCs remain nucleated. (More? Spleen Development)
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Hindgut - distral transverse colon, descending colon, sigmoid colon, rectum and cloaca. The cloaca is the common urogenital sinus which will later become partitioned into an anterior urinary and posterior GIT rectal component. (More? Urogenital Development) |
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Overview of GIT Formation | Abnormalities | Stage 13/14 Overview | Stage 13/14 | Stage 22 | Selected stage 22 | Histology | Liver | Gall Bladder | Spleen | Pancreas | Stomach | Folding | Intestine | Sensory Development - Taste | Head and Neck Development - Tongue
Endoderm (164 Kb) Features: gastrointestinal tract, yolk stalk, yolk sac, allantois |
Endoderm large version(270 Kb) Features: gastrointestinal tract, yolk stalk, yolk sac, allantois |
Stomach Rotation (326 Kb) |
Stomach Rotation large version (620 Kb) |
Lesser Sac superior view (104 Kb) |
Lesser Sac ventrolateral view (408 Kb) |
Hindgut (364 Kb) |
Cloaca (276 Kb) |
Formation of Definitive Gut (315 Kb)
(More? GIT Movies| Human Development Movies)
Embryo Images Unit: Gut Development | Gut Formation (Week 4) | Early Foregut (Weeks 4-6) | Early Midgut (Week 5) | Late Foregut (Weeks 5-10) | Late Midgut (Weeks 7-10) | Hindgut |
(More? Embryo Images Online)
GIT shown in green anchored by dosal and ventral mesogastrium. The space ouside this will be the peritoneal cavity.
Red ring-neural tube with neural crest
Blue ring- notocord
Orange- somites
Differentiation of associated organs at the level of the forming stomach occurs both dorsally (spleen) and ventrally (liver).
Large blue ring- dorsal
aorta
Dark green ring- Liver
Continued growth of the GIT and the organs leads to organ movements and bending of tract.
Other Images: Simple cartoon of GIT Rotation | Greater Omentum | Duodenum/Pancreas Rotation |
Below is an overview of the sections starting at the level of pharynx compressed dorsoventrally, following the GIT through to the rectum. The most obvious feature is that of a continuous tube initially, attached by dorsoventral mesentry. Outside this tube and mesentry (at the levels below the lung buds) is the intraembryonic coelom that will form the peritoneal cavity. The hepatic diverticulum (liver bud) lies under the septum transversum is the earliest associated GIT organ that has differentiated, and now occupies a substantial region of the abdomen. A full description of each image is on the stage13/14 page. Clicking on sections below will open the original images.
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Bifurcation of the pharynx into anterior respiratory and posterior oesophagous. |
The stomach forming beneath the lung buds and adjacent to the developing liver. |
Below the stomach the GIT has a large dorsal mesogastrium and finer ventral mesogastrium. Associated with the tract is the large portal blood vessel derived from the vitelline circulation. |
At the bottom curvature of the embryo the mesentry association with the GIT shows extensive vitelline vessels running out through the umbilicus. The hindgut can then be seen, ending at the common urogenital sinus, the cloaca. |
Links: Journals | Online Textbooks | Search Textbooks | Reviews | Articles | 1999 Refs | Search PubMed | Glossary
Specific references can also be found on each notes page and an earlier search for Selected GIT References 1999.
Developmental Biology (6th ed) Gilbert, Scott F. Sunderland (MA): Sinauer Associates, Inc.; c2000. The Digestive Tube and Its Derivatives | Endodermal development of a human embryo
Search NLM Online Textbooks "gastrointestinal tract" : Developmental Biology | Endocrinology | Molecular Biology of the Cell | The Cell- A molecular Approach
Reviews
Young HM. On the outside looking in: longitudinal muscle development in the gut. Neurogastroenterol Motil. 2008 May;20(5):431-3.
Neu J. Gastrointestinal development and meeting the nutritional needs of premature infants. Am J Clin Nutr. 2007 Feb;85(2):629S-634S.
Anderson RB, Newgreen DF, Young HM. Neural crest and the development of the enteric nervous system. Adv Exp Med Biol. 2006;589:181-96.
Costa RH, Kalinichenko VV, Holterman AX, Wang X. Transcription factors in liver development, differentiation, and regeneration. Hepatology. 2003 Dec;38(6):1331-47.
de Santa Barbara P, van den Brink GR, Roberts DJ. Development and differentiation of the intestinal epithelium. Cell Mol Life Sci. 2003 Jul;60(7):1322-32.
Johnson LR. Functional development of the stomach. Annu Rev Physiol. 1985;47:199-215. Review.
Articles
Wilm B, Ipenberg A, Hastie ND, Burch JB, Bader DM. The serosal mesothelium is a major source of smooth muscle cells of the gut vasculature. Development. 2005 Dec;132(23):5317-28.
"Our studies show that the gut is initially devoid of a mesothelium but that serosal mesothelial cells expressing the Wilm's tumor protein (Wt1) move to and over the gut. Subsequently, a subset of these cells undergoes epithelial-mesenchymal transition (EMT) and migrates throughout the gut. ...these cells differentiate to smooth muscle of all major blood vessels in the mesenteries and gut."
Search Mar 2007 "gastrointestinal tract development" 29,361 reference articles of which 3,494 were reviews. (More? Neural Crest Reviews References 1999)
Search PubMed: term = gastrointestinal tract development | embryonic stomach development | embryonic small intestine development |
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This section of notes covers development of the gastrointestinal tract and it associated organs.
Gastrulation, or gut formation, was historically the easiest observable feature of frog development Frog Development).
This formation of the "internal epithelia" of the gastrointestinal tract can be seen simply as a continuous tube from end to end, which is the same yet different along its length. Then add to this the tethering of this tube to the body wall, connection with associated organs (liver, pancreas), a unique portal vasculature and its own neuro/endocrine system it becomes more complex. Finally this tube grows in length partly outside the body and mechanically folds in a balletic rotation so as too not block its own vasularization.
There is a lot more to the development of this simple tube.
Please email Dr Mark Hill if you wish to make a comment about this current project.
