Gastrointestinal Tract - Intestine Development

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Contents

Introduction

midgut herniation

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.


GIT Links: Introduction | Medicine Lecture | Science Lecture | Endoderm | Stomach | Liver | Gall Bladder | Pancreas | Intestine | Tongue | Taste | Stage 13 | Stage 22 | Abnormalities | Movies | Postnatal | Milk | Tooth | Tongue | BGD Lecture | BGD Practical | Category:Gastrointestinal Tract


GIT Histology Links: Upper GIT | Salivary Gland | Smooth Muscle Histology | Liver | Gall Bladder | Pancreas | Colon | Histology Stains | Histology | GIT Development
Historic Embryology: 1912 Small Intestine | 1912 large Intestine

Some Recent Findings

Model for cloacal septation[1]
  • Bmp7 functions via a polarity mechanism to promote cloacal septation[1] "During normal development in human and other placental mammals, the embryonic cloacal cavity separates along the axial longitudinal plane to give rise to the urethral system, ventrally, and the rectum, dorsally. Defects in cloacal development are very common and present clinically as a rectourethral fistula in about 1 in 5,000 live human births. Yet, the cellular mechanisms of cloacal septation remain poorly understood. ...Our results strongly indicate that Bmp7/JNK signaling regulates remodeling of the cloacal endoderm resulting in a topological separation of the urinary and digestive systems. Our study points to the importance of Bmp and JNK signaling in cloacal development and rectourethral malformations."
  • Fgf9 signaling regulates small intestinal elongation and mesenchymal development [2] "Short bowel syndrome is an acquired condition in which the length of the small intestine is insufficient to perform its normal absorptive function. ...These data suggest a model in which epithelial-derived Fgf9 stimulates intestinal mesenchymal stem cells (iMSCs) that in turn regulate underlying mesenchymal fibroblast proliferation and differentiation at least in part through inhibition of Tgfbeta signaling in the mesenchyme."

Adult Intestine

Duodenum
Adult jejunum histology

Intestinal Regions

Small intestine or bowel length (see also Fetal Intestine Length and Small Intestine Length)

  • 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

Stage13-GIT-icon.jpg
Quicktime | Flash

Week 8

Stage22-GIT-icon.jpg
Quicktime | Flash

Stage 22 image 088.jpg Stage 22 image 089.jpg

Late embryonic small intestine commencing at the duodenum, continuing as ventrally herniated and returning to join the colon.

Links: Carnegie stage 22 | Week 8

Rotation

Normal intestinal rotation cartoon.jpg

Normal intestinal rotation[3]

Fetal Intestine Length

Fetal small Intestine length growth graph.jpg Fetal large Intestine length growth graph.jpg
Fetal small Intestine length growth Fetal Large Intestine length growth

Data from [4][5]

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.[6]

Age (weeks gestational age) Average Length (cm)
20 125
30 200
term 275
1 year postnatal 380
5 years 450
10 years 500
20 years 575

Table data based upon 8 published reports of necropsy measurement of 1010 guts.[6]

Intestinal Motility

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.[7]

Neural Crest

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 (Auerbach's plexus, named after Leopold Auerbach (1828–1897) a German anatomist and neuropathologist.)

  • is first formed plexus
  • lies between the outer longitudinal and inner circular layers of muscularis externa
  • provides motor innervation to both layers
  • secretomotor innervation to the mucosa
  • has both parasympathetic and sympathetic input

Submucosal Plexus (Meissner's plexus, named after Georg Meissner (1829–1905) a German anatomist and physiologist.)

  • forms 2-3 days after the myenteric plexus
  • formed by cells migrating from the myenteric plexus
  • innervates smooth muscle of the muscularis mucosae
  • has only parasympathetic fibers

Smooth Muscle

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

Abnormalities

Abnormality Links: Gastrointestinal Tract - Abnormalities | Intestine Development | Gastrointestinal Tract
Links: Gastrointestinal Tract - Abnormalities | Image - Small intestine duplication

Appendix Duplication

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[8] and a later modified by Wallbridge in 1963[9], subsequently two more types of appendix abnormalities have been identified.[10][11]

Modified Cave-Wallbridge Classification (table from[12])

Classification of types
of appendix duplication
Features
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.[13]

  • reduces gut function for digestion and absorption of nutrients (intestinal failure).


Links: PubMed Health | Better Health

Molecular Factors

  • Cdx (Caudal-type homeobox) group of ParaHox genes (mouse Cdx1, Cdx2 and Cdx4)[14]
  • FGF9

References

  1. 1.0 1.1 Kun Xu, Xinyu Wu, Ellen Shapiro, Honging Huang, Lixia Zhang, Duane Hickling, Yan Deng, Peng Lee, Juan Li, Herbert Lepor, Irina Grishina Bmp7 functions via a polarity mechanism to promote cloacal septation. PLoS ONE: 2012, 7(1);e29372 PMID:22253716
  2. Michael J Geske, Xiuqin Zhang, Khushbu K Patel, David M Ornitz, Thaddeus S Stappenbeck Fgf9 signaling regulates small intestinal elongation and mesenchymal development. Development: 2008, 135(17);2959-68 PMID:18653563
  3. Vicki Martin, Charles Shaw-Smith Review of genetic factors in intestinal malrotation. Pediatr. Surg. Int.: 2010, 26(8);769-81 PMID:20549505 | PMC2908440
  4. J FitzSimmons, A Chinn, T H Shepard Normal length of the human fetal gastrointestinal tract. Pediatr Pathol: 1988, 8(6);633-41 PMID:3244599
  5. John G Archie, Julianne S Collins, Robert Roger Lebel Quantitative standards for fetal and neonatal autopsy. Am. J. Clin. Pathol.: 2006, 126(2);256-65 PMID:16891202
  6. 6.0 6.1 L T Weaver, S Austin, T J Cole Small intestinal length: a factor essential for gut adaptation. Gut: 1991, 32(11);1321-3 PMID:1752463 | PMC1379160 | Gut.
  7. Alan J Burns, Rachael R Roberts, Joel C Bornstein, Heather M Young Development of the enteric nervous system and its role in intestinal motility during fetal and early postnatal stages. Semin. Pediatr. Surg.: 2009, 18(4);196-205 PMID:19782301
  8. A J Cave Appendix Vermiformis Duplex. J. Anat.: 1936, 70(Pt 2);283-92 PMID:17104589
  9. P H WALLBRIDGE Double appendix. Br J Surg: 1962, 50();346-7 PMID:13998581
  10. T W Mesko, R Lugo, T Breitholtz Horseshoe anomaly of the appendix: a previously undescribed entity. Surgery: 1989, 106(3);563-6 PMID:2772830
  11. L F Tinckler Triple appendix vermiformis--a unique case. Br J Surg: 1968, 55(1);79-81 PMID:5635427
  12. Emel Canbay, Emel Akman Appendix perforation in appendix duplication in a man: a case report. J Med Case Reports: 2011, 5();162 PMID:21513538 | J Medical Case Reports | PDF
  13. G Davì, A Pinto, M G Palumbo, V Gallo, A Mazza, A Strano Dipyridamole and aspirin in arteriosclerosis obliterans of the lower limbs. Adv. Prostaglandin Thromboxane Leukot. Res.: 1985, 13();271-5 PMID:3159212
  14. Felix Beck, Emma J Stringer The role of Cdx genes in the gut and in axial development. Biochem. Soc. Trans.: 2010, 38(2);353-7 PMID:20298182

Reviews

Taeko K Noah, Bridgitte Donahue, Noah F Shroyer Intestinal development and differentiation. Exp. Cell Res.: 2011, 317(19);2702-10 PMID:21978911

Alan J Burns, Rachael R Roberts, Joel C Bornstein, Heather M Young Development of the enteric nervous system and its role in intestinal motility during fetal and early postnatal stages. Semin. Pediatr. Surg.: 2009, 18(4);196-205 PMID:19782301


Articles

Tae-Hee Kim, Byeong-Moo Kim, Junhao Mao, Sheldon Rowan, Ramesh A Shivdasani Endodermal Hedgehog signals modulate Notch pathway activity in the developing digestive tract mesenchyme. Development: 2011, 138(15);3225-33 PMID:21750033


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Cite this page: Hill, M.A. (2014) Embryology Gastrointestinal Tract - Intestine Development. Retrieved April 23, 2014, from http://embryology.med.unsw.edu.au/embryology/index.php?title=Gastrointestinal_Tract_-_Intestine_Development

What Links Here?
Dr Mark Hill 2014, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
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