Gastrointestinal Tract - Intestine Development: Difference between revisions
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[[File:Fetal small Intestine length growth graph.jpg| | {| | ||
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Data from <ref><pubmed>3244599</pubmed></ref><ref><pubmed>16891202</pubmed></ref> | |||
==Small Intestine Length== | ==Small Intestine Length== |
Revision as of 00:46, 1 June 2011
Introduction
The part of the gastrointestinal tract (GIT) lying between the stomach and anus, is described as the intestines 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
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Adult Intestine
Intestinal Regions
Small intestine or bowel
- Duodenum (adult 25 cm length)
- Jejunum (adult 1.4 m length)
- Ileum (adult 3.5 m length)
Large intestine or bowel
- Cecum (caecum)
- Vermiform appendix ("appendix", adult 2 to 20 cm length)
- Colon
- Ascending colon (adult 25 cm length)
- Transverse colon
- Descending colon
- Sigmoid colon
Intestinal Functions
Small Intestine
- absorption of nutrients and minerals found in food
- Duodenum -principal site for iron absorption
Cecum
- connects the ileum with the ascending colon
- separated by the ileocecal valve (ICV, Bauhin's valve)
- connected to the vermiform appendix ("appendix")
Colon
- absorbs fluid, water and salts, from solid wastes
- site of commensal bacteria (flora) fermentation of unabsorbed material
Embryonic Development
Week 4
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Week 8
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Late embryonic small intestine commencing at the duodenum, continuing as ventrally herniated and returning to join the colon.
- Links: Carnegie stage 22 | Week 8
Fetal Intestine Length
Fetal small Intestine length growth | Fetal Large Intestine length growth
Small Intestine LengthSmall 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.[4]
Table data based upon 8 published reports of necropsy measurement of 1010 guts.[4] Intestinal MotilityThe 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.[5] Neural Crestweek 5 - migrating neural crest cells reach the midgut week 7 - neural crest cells have colonized the entire gut
Myenteric plexus (Auerbach's plexus, named after Leopold Auerbach (1828–1897) a German anatomist and neuropathologist.)
Submucosal Plexus (Meissner's plexus, named after Georg Meissner (1829–1905) a German anatomist and physiologist.)
Smooth Muscleweek 8 - esophagus circular muscle week 11 - hindgut circular muscle week 14 - hindgut concentric muscularis mucosae, circular muscle, and longitudinal muscle Interstitial Cells of CajalInterstitial 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
Abnormalities
Cite this page: Hill, M.A. (2024, May 21) Embryology Gastrointestinal Tract - Intestine Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Gastrointestinal_Tract_-_Intestine_Development
Appendix DuplicationAppendix 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[6] and a later modified by Wallbridge in 1963[7], subsequently two more types of appendix abnormalities have been identified.[8][9] Modified Cave-Wallbridge Classification (table from[10])
Molecular Factors
References
Reviews<pubmed>19782301</pubmed> ArticlesSearch PubmedSearch Bookshelf Intestine Development
Glossary Links
Cite this page: Hill, M.A. (2024, May 21) Embryology Gastrointestinal Tract - Intestine Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Gastrointestinal_Tract_-_Intestine_Development
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