Gastrointestinal Tract - Intestine Development
|Embryology - 17 Oct 2019 Expand to Translate|
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- 1 Introduction
- 2 Some Recent Findings
- 3 Small Intestine
- 4 Large Intestine
- 5 Embryonic Development
- 6 Rotation
- 7 Fetal Intestine Length
- 8 Small Intestine Length
- 9 Appendix
- 10 Hindgut
- 11 Intestinal Motility
- 12 Abnormalities
- 13 Molecular Factors
- 14 References
- 15 Additional Images
- 16 External Links
- 17 Glossary Links
The part of the gastrointestinal tract (GIT) lying between the stomach and anus, is described as the intestine or bowel. This region is further divided anatomically and functionally into the small intestine or bowel (duodenum, jejunum and ileum) and large intestine or bowel (cecum and colon). Initially development concerns the midgut region, connected to the yolk sac, and the hindgut region, ending at the cloacal membrane. This is followed by two mechanical processes of elongation and rotation. Elongation, growth in length, leaves the midgut "herniated" at the umbilicus and external to the abdomen. Rotation, around a mesentery axis, establishes the anatomical position of the large intestine within the peritoneal space.
Migration of neural crest cells into the wall establishes the enteric nervous system, which has a role in peristalsis and secretion. Prenatally, secretions also accumulate in this region and are the first postnatal bowel movement, the meconium.
The small intestine grows in length rapidly in the last trimester, at birth it is about half the eventual adult length (More? Small Intestine Length). Like most of the gut, this region is not "functional" until after birth, when development continues by populating the large intestine with commensal bacteria and the establishment of the immune structure in the wall.
Some Recent Findings
|More recent papers|
This table allows an automated computer search of the external PubMed database using the listed "Search term" text link.
|These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table.
The small intestine (or bowel) consists of 3 main anatomical regions. A notable feature of this epithelium is the continuous replacement throughout life, from a stem cell population residing in the crypts, migrating towards the tips of the villi.
- Duodenum (25 cm)
- Jejunum (1.4 m)
- Ileum (3.5 m)
The duodenum develops from the part of the tube immediately after the stomach and uniquely forms the junction between foregut (upper) and midgut (lower). Unlike the remainder of the small intestine it grows significantly less in overall length. Initially suspended by a mesentery, and projects forward in the form of a loop, both of which rotate with the fusion of the two pancreatic buds, and subsequently displaced by the transverse colon. The right surface of the duodenal mesentery is directed backward to parietal peritoneum and becomes retroperitoneal. Both the biliary and the pancreatic ducts empty into the duodenum.
|Note the distinctive "star-shaped" lumen of duodenum and the developing muscular wall.
The pancreas and its duct can also be seen on the right of image.
- Search PubMed: Duodenum Development
Adult jejunum histology
Search PubMed: Jejunum Development
The adult ileum contains specialised aggregated lymphoid nodules known as Peyer's patches.
Adult ileum Peyer's patches
Search PubMed: Ileum Development
Large intestine or bowel
- Cecum (caecum)
- Vermiform appendix ("appendix", adult 2 to 20 cm length)
- Ascending colon (adult 25 cm length)
- Transverse colon
- Descending colon
- Sigmoid colon
- absorption of nutrients and minerals found in food
- Duodenum -principal site for iron absorption
- connects the ileum with the ascending colon
- separated by the ileocecal valve (ICV, Bauhin's valve)
- connected to the vermiform appendix ("appendix")
- absorbs fluid, water and salts, from solid wastes
- site of commensal bacteria (flora) fermentation of unabsorbed material
Human embryo small intestine secondary loops (week 7 to 8).
Late embryonic small intestine commencing at the duodenum, continuing as ventrally herniated and returning to join the colon.
Small intestine tertiary loops week 8.
A recent 3 dimensional study has suggested a modified “en-bloc rotation” of the small intestine, compared the the earlier simplified description of 270 degree rotation (below).
Human intestine “en-bloc rotation” model.
- "If one insists on using the term rotation for this movement, it would be largely around a craniocaudal axis (in the transverse plane) rather than a dorsoventral axis (frontal plane). In view of the brief time window and orientation of the apparent rotational axis, we conclude that the distal ileum and cecum “slide” rather than “rotate” as from the umbilical orifice to the lower-right abdominal cavity."
Normal intestinal rotation
Fetal Intestine Length
|Fetal small Intestine length growth||Fetal Large Intestine length growth|
Small Intestine Length
Small intestine growth in length is initially linear (first half pregnancy to 32 cm CRL), followed by rapid growth in the last 15 weeks doubling the overall length. Growth continues postnatally but after 1 year slows again to a linear increase to adulthood.
|Age (weeks gestational age)||Average Length (cm)|
|1 year postnatal||380|
Table data based upon 8 published reports of necropsy measurement of 1010 guts.
The appendix (vermiform appendix, vermix) is a finger-like diverticulum located anatomically at the cecum, the junction between the small and large intestines (colon). The length (2.5-13 cm) is longer in both infants and children and also has more abundant lymphatic tissue in early life. The wall structure is similar to the small intestine (though with no villi), nor plicae circularis. Its immune function is associated with the many lymph nodules surrounding the lumen that extend from the mucosa into the submucosa. It has also been suggested as a repository for beneficial intestinal microflora. See also the review comparing the appendix in different species.
There appears to be a developmental anatomical differences in the fetal position of the appendix in males and females. In the fetus, lymphocyte aggregates first appear in this region during the second trimester, week 15 (GA week 17).
Historically, Berengario da Carpi (1460-c.1530) in Commentaria cum amplissimis additionibus super Anatomia Mundini (1521) was the first to describe the human appendix.
See also notes on appendix duplication.
Anatomically the distal third of the transverse colon and the splenic flexure, the descending colon, sigmoid colon and rectum. The developmental timing of the anus and rectum formation in human embryos of the Carnegie Collection has been previously carried out (1974). A more recent study has also been made of the Kyoto Collection embryos.
There has been some recent controversy over the "anal membrane" formation.
The enteric nervous system neural crest-derived neurons interacts with the circular and longitudinal smooth muscle layers and the interstitial cells of Cajal to generate motility. The developmental timing data shown below is from a recent review.
week 5 - migrating neural crest cells reach the midgut
week 7 - neural crest cells have colonized the entire gut
- colonization occurs in a rostro-caudal sequence
|Myenteric plexus||Submucosal plexus|
|Auerbach's plexus||Meissner's plexus|
|Leopold Auerbach (1828–1897) a German anatomist and neuropathologist.||Georg Meissner (1829–1905) a German anatomist and physiologist.|
|Links: enteric nervous system | intestine | neural crest | PMID 25428846|
week 8 - esophagus circular muscle
week 11 - hindgut circular muscle
week 14 - hindgut concentric muscularis mucosae, circular muscle, and longitudinal muscle
Interstitial Cells of Cajal
Interstitial cells of Cajal (ICC) are electrical pacemaker cells within the gastrointestinal tract smooth muscle. They create the basal (slow waves) rhythm required for contraction and peristalsis. They are mesodermal in origin.
weeks 7-9 - cells initially appear
week 11 - distinct clusters
week 12-14 - clustered around myenteric ganglia along the entire gut
- Links: Neural Crest Development
- Abnormality Links: Gastrointestinal Tract - Abnormalities | Intestine Development | Gastrointestinal Tract
- Lumen Abnormalities: Image - Duplication sites | Pyloric atresia | Jejunal atresia
- Rotation: Image - Midgut volvulus | Image - Intestinal malrotation | Image - Cecal volvulus | Image - Sigmoid volvulus | Ladd's band
- Meckel's Diverticulum: Meckel's Image 1 | Meckel's Image 2 | Meckel's Image 3 |
- Intestinal Aganglionosis: Image - Ostomy | Image - Stoma | Surgery 1 | Surgery 2 | Surgery 3
Appendix duplication is an extremely rare congenital anomaly (0.004% to 0.009% of appendectomy specimens) first classified according to their anatomic location by Cave in 1936 and a later modified by Wallbridge in 1963, subsequently two more types of appendix abnormalities have been identified.
Modified Cave-Wallbridge Classification (table from)
|Classification of types
of appendix duplication
|A||Single cecum with various degrees of incomplete duplication|
|B1 (bird type)||Two appendixes symmetrically placed on either side of the ileocecal valve|
|B2 (tenia coli type)||ne appendix arises from the cecum at the usual site, and the second
appendix branches from the cecum along the lines of the tenia at various distances from the first
|B3||One appendix arises from the usual site, and the second appendix arises from
the hepatic flexura
|B4||One appendix arises from the usual site, and the second appendix arises from
the splenic flexura
|C||Double cecum, each with an appendix|
|Horseshoe appendix||One appendix has two openings into a common cecum|
|Triple appendix||One appendix arises from the cecum at the usual site, and two additional appendixes arise from the colon|
Short Bowel Syndrome
Short bowel syndrome (SBS) results typically due to developmental abnormalities, extensive intestinal resection during the neonatal period, or necrotising enterolitis.
- reduces gut function for digestion and absorption of nutrients (intestinal failure).
- Cdx (Caudal-type homeobox) group of ParaHox genes (mouse Cdx1, Cdx2 and Cdx4)
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- Wang S, Cebrian C, Schnell S & Gumucio DL. (2018). Radial WNT5A-Guided Post-mitotic Filopodial Pathfinding Is Critical for Midgut Tube Elongation. Dev. Cell , 46, 173-188.e3. PMID: 30016620 DOI.
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- Hashimoto R. (2013). Development of the human tail bud and splanchnic mesenchyme. Congenit Anom (Kyoto) , 53, 27-33. PMID: 23480355 DOI.
- Li FF, Zhang T, Bai YZ, Yuan ZW & Wang WL. (2011). Spatiotemporal expression of Wnt5a during the development of the hindgut and anorectum in human embryos. Int J Colorectal Dis , 26, 983-8. PMID: 21431850 DOI.
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Search Bookshelf Intestine Development
|Historic Disclaimer - information about historic embryology pages|
|Embryology History | Historic Embryology Papers)|
Tandler J. The development of the human duodenum in early embryonic stages. (Zur Entwicklungsgeschichte des menschlichen Duodenum in frṻhen Embryonalstadien) (1900) Morphol. Jahrb. 29:187-216.
Tandler (1900) was the first to recognize that the lumen of the duodenum in embryos between " 30 to 60 days," is normally "more or less completely" obliterated.
Frazer JE. and Robbins RH. On the factors concerned in causing rotation of the intestine in man. (1915) J Anat Physiol. 50(1): 75-110. PMID 17233053
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Cite this page: Hill, M.A. (2019, October 17) Embryology Gastrointestinal Tract - Intestine Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Gastrointestinal_Tract_-_Intestine_Development
- © Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G