BGDB Gastrointestinal - Late Embryo
|Practical 1: Trilaminar Embryo | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities | Lecture | Quiz|
We have now reached late embryonic development. Start by looking briefly the process of how the definitive GIT tube is formed and then at the overview of the Carnegie stage 22 embryo GIT from one end to the other. The tract now has a different appearance at different levels; stomach, duodenum, midgut and hindgut.
Then work through the listed specific serial sections of the embryo identifying the GIT features. Alternatively step through the serial sections yourself identifying the tract, its associated mesentries, organs and spaces. Note you should also be comparing the GIT appearance with the earlier embryonic 13 Carnegie stage.
Human Embryo MRI at the end of embryonic development (GA week 10).
|Human Embryo (Carnegie stage 22, week 8, GA week 10)||A 3D reconstruction of the gastrointestinal tract.||The developing esophagus.|
|E6L||Liver. Ductus venosus.
Cardio-oesophageal junction (cf. E5).
Inferior vena cava.
|E7L||Stomach body, with mucosa, submucosa and muscularis externa.
Lesser sac. Lesser omentum. Pyloroduodenal junction. Folded duodenal mucosa.
Inferior vena cava. Portal vein. Hepatic ducts. Gallbladder.
|F1L||Stomach body. Spleen. Pyloric canal. Duodenum.
Small intestine loop (jejunum) cut tangentially, ventral to liver.
|F2L||Stomach, spleen. Superior mesenteric artery.
Superior mesenteric vein crossing cranial to body of pancreas.
Tail of pancreas.
Small intestinal loop herniating from abdominal cavity into the coelom of the umbilical cord (remnant of extra-embryonic coelom).
|F4L||Greater curvature of stomach (tangential section). Lesser sac. Greater omentum. Duodenal/jejunal junction.
Note colon (small lumen, darkly-staining wall) and its mesocolon.
Note the sections of small and large intestine within the umbilical cord coelom and their mesenteries.
Note the thickened jelly to one side of the umbilical cord, containing umbilical vein and R umbilical artery.
|F5L||Lesser sac. Greater omentum. Duodenum. Jejunum (cut twice with mesentery in between). Colon and mesocolon.|
|F6L||Greater omentum and lesser sac.
Jejunum with mesentery.
Colon with mesocolon.
Three layers of abdominal muscles.
Both umbilical arteries now inside abdominal cavity with urachus between them.
|F7L||In abdominal cavity - colon with mesocolon, jejunum. Greater omentum and lesser sac.
Umbilical cord - containing umbilical arteries and small dark allantois. Umbilical cord coelom containing mainly, small intestinal loops with their mesentery.
||Umbilical cord and coelom containing small intestine loops.
Colon and mesocolon. Jejunum (G1 only).
Bladder with umbilical arteries either side.
Umbilical arteries arising from common iliac arteries.
|G5L||Recto-anal junction with rectovesical pouch of peritoneal cavity.|
|G6L||Anal canal with triangular lumen.|
This is a simplified animation showing how the gastrointestinal tract wall changes during the late embryonic period.
Week 8 - By the end of this week the GIT endoderm tube is a tube once more.
Week 9 - (early fetal) the endoderm of this now hollow tube differentiates into the mucosal epithelium (endoderm).
|Page | Play|
- Splanchnic mesoderm will form the submucosa connective tissue and smooth muscle (circular and longitudinal) layers (mesoderm).
- Neural crest cells migrate into this tissue and will form the nerve plexus innervation (ectoderm).
Neural Crest colonization occurs in a rostro-caudal sequence forming the 2 associated plexuses.
- week 5 - migrating neural crest cells reach the midgut
- week 7 - neural crest cells have colonized the entire gut
|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|
Interstitial cells of Cajal (ICCs) - may be mesenchymal in origin, develop within the myenteric plexus and are pacemaker cells that control peristaltic contraction waves.
Cholangiocytes=== Epithelial cells that line the intra- and extrahepatic ducts of the biliary tree. These cells modify the hepatocyte-derived bile, and are regulated by hormones, peptides, nucleotides, neurotransmitters, and other molecules.
Human (week 4) organ development
|Note that while the spleen is not a gastrointestinal tract organ, part of the Immune System, it is often described with this system as it develops within the dorsal mesentery. During embryonic development it has a haematopoietic function, with residing blood stem cells, before fetal bone marrow relocation of this population. The adult spleen structure and function was covered in an earlier SH Lecture.|
|Virtual Slide Features - Stage 22 Liver|
|Virtual Slide - Stage 22 Liver and Ductus Venosus All Virtual Slides
The links shown in the table below are to specific features shown on the Human embryo (stage 22) Liver and Ductus Venosus virtual slide. See also notes on Liver Development
Clicking the text will open the slide at a detailed view with the structure generally located in the centre of the view. The slide then can also be zoomed out from the set magnification using the controls in the upper left or the mouse.
Use your browser back button to return to this table.
|You can also make your own selected feature view.
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|E3 Overview of liver region for selected high power views shown below. Note the position and size of the developing liver spanning the entire abdomen and within the liver the large central ductus venosus.|
|E4 Central veins of liver. Radiating appearance of hepatic sinusoids. unlabeled version|
|E5 Central vein with endothelial lining, containing nucleated erythrocytes, fetal red blood cells. The fetal liver has an important haemopoietic role. unlabeled version|
The Adult Liver Lobule
- Links: liver
Exocrine Function - Pancreatic amylase digests starch to maltose. Postnatally, a blood test to detect amylase can be used to diagnose and monitor acute or chronic pancreatitis (pancreas inflammation).
The initial formation of the pancreas as two separate lobes each with their own duct that fuses leads a range of anatomical variations in the adult exocrine pancreatic duct. Pancreatic duct five variation classification: common, ansa pancreatica, branch fusion, looped, and separated. Accessory pancreatic duct (APD, of Santorini) in the embryo is the main drainage duct of the dorsal pancreatic bud emptying into the minor duodenal papilla. In the adult it has been further classified as either long-type (joins main pancreatic duct at pancreas neck portion) and short-type (joins main pancreatic duct near first inferior branch).
- Main Pancreatic Duct (MPD or Wirsung's duct) forms within the dorsal pancreatic bud and is present in the body and tail of the pancreas. Discovered by Johann Georg Wirsung (1589 - 1643) a German physician who worked as a prosector in Padua.
- Accessory Pancreatic Duct (APD or Santorini’s duct) is present mainly in the head of the pancreas. Originally dissected and delineated by Giovanni Domenico Santorini (1681 - 1737) an Italian anatomist.
- Endoscopic Retrograde Cholangiopancreatography (ERCP) is a medical procedure which allows an injected dye to display the duct system on an x ray (pancreatograms).
Human (week 8, Stage 22) pancreas
- Functions - exocrine (amylase, alpha-fetoprotein) and endocrine (pancreatic islets)
- Pancreatic buds - endoderm, covered in splanchnic mesoderm
- Pancreatic bud formation - duodenal level endoderm, splanchnic mesoderm forms dorsal and ventral mesentery, dorsal bud (larger, first), ventral bud (smaller, later)
- Duodenum growth/rotation - brings ventral and dorsal buds together, fusion of buds
- Pancreatic duct - ventral bud duct and distal part of dorsal bud, exocrine function
- Islet cells- cords of endodermal cells form ducts, which cells bud off to form islets
Epitheilal/mesenchymal (ectoderm first pharyngeal arch and neural crest ectomesenchymal cells) interactions in development and has a major contribution from the neural crest. This has been described as 5 stages of development from late embryonic through early fetal period forming the deciduous teeth. Humans have 2 sets of teeth, the deciduous and then the adult teeth that replace them. (More? tooth)
|lamina||Week 6||E 11|
|placode||Week 7||E 11.5|
|bud||Week 8||E 12.5|
|cap||Week 11||E 14.5|
|bell||Week 14||E 15.5|
Fetal incisor tooth at 6 months
|Gastrointestinal Tract Terms|
|Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page.|
- Carnegie stage 14 to 17 (week 4-6, GA week 6-8) - appears as a bulge in the dorsal mesogastrium.
- Carnegie stage 20 (week 8, GA week 10) - the spleen is apparent.
- Intra-splenic folds appear later.
- Rate of increase in spleen length in relation to that of stomach length along the cranial-caudal direction remained constant during 19 - 23.
|Spleen Development Timeline|
- week 15 (GA 17 weeks) - alpha-smooth muscle actin (alpha-SMA)-positive reticulum cells scattered around the arterioles.
- week 18 to 21 (GA 20 - 23 weeks) - alpha-SMA-positive reticulum cells increase in number and began to form a reticular framework. An accumulation of T and B lymphocytes occurred within the framework, and a primitive white pulp was observed around the arterioles.
- week 22 (GA 24 weeks) - antigenic diversity of the reticular framework was observed, and T and B lymphocytes were segregated in the framework. T lymphocytes were sorted into the alpha-SMA-positive reticular framework, and the periarteriolar lymphoid sheath (PALS) was formed around the arteriole. B lymphocytes aggregated in eccentric portions to the PALS and formed the lymph follicle (LF). The reticular framework of the LF was alpha-SMA-negative.
- week 24 (GA 26 weeks) - marginal zone appeared in the alpha-SMA-positive reticular framework around the white pulp.
- Links: spleen
Embryonic Liver Timeline
The table below is a detailed timeline overview of human liver development.
|Carnegie Stage||Age (days)||CRL (mm)||Biliary system||Vascular||Hepatic parenchyma|
|21||53||22.5||Bile duct morphology as earlier stage. Common bile duct empties at the level of the proximal duodenum.||
||Hepatic parenchyma a large rounded mass.|
|23||58||27||Bile duct morphology as earlier stage.||
|Data from a recent human study|
Epithelial cells that line the intra- and extrahepatic ducts of the biliary tree. These cells modify the hepatocyte-derived bile, and are regulated by hormones, peptides, nucleotides, neurotransmitters, and other molecules.
- Three-dimensional reconstructions of intrahepatic bile duct tubulogenesis in human liver
- initial transition of primitive hepatocytes into cholangiocytes shaping the ductal plate
- process of maturation and remodeling where the intrahepatic biliary tree develops through an asymmetrical form of cholangiocyte tubulogenesis.
- Review - PAX9 gene mutations and tooth agenesis "Paired box 9 (PAX9) is one of the best-known transcription factors involved in the development of human dentition. Mutations in PAX9 gene could, therefore, seriously influence the number, position and morphology of the teeth in an affected individual. To date, over 50 mutations in the gene have been reported as associated with various types of dental agenesis (congenitally missing teeth) and other inherited dental defects or variations. The most common consequence of PAX9 gene mutation is the autosomal-dominant isolated (non-syndromic) oligodontia or hypodontia. In the present review, we are summarizing all known PAX9 mutations as well as their nature and precise loci in the DNA sequence of the gene."
- Radenkovic G, Radenkovic D & Velickov A. (2018). Development of interstitial cells of Cajal in the human digestive tract as the result of reciprocal induction of mesenchymal and neural crest cells. J. Cell. Mol. Med. , 22, 778-785. PMID: 29193736 DOI.
- Godlewski G, Gaubert-Cristol R, Rouy S & Prudhomme M. (1997). Liver development in the rat and in man during the embryonic period (Carnegie stages 11-23). Microsc. Res. Tech. , 39, 314-27. PMID: 9407542 <314::AID-JEMT2>3.0.CO;2-H DOI.
- Godlewski G, Gaubert-Cristol R, Rouy S & Prudhomme M. (1997). Liver development in the rat during the embryonic period (Carnegie stages 15-23). Acta Anat (Basel) , 160, 172-8. PMID: 9718390
- Endo A, Ueno S, Yamada S, Uwabe C & Takakuwa T. (2015). Morphogenesis of the spleen during the human embryonic period. Anat Rec (Hoboken) , 298, 820-6. PMID: 25403423 DOI.
- Satoh T, Sakurai E, Tada H & Masuda T. (2009). Ontogeny of reticular framework of white pulp and marginal zone in human spleen: immunohistochemical studies of fetal spleens from the 17th to 40th week of gestation. Cell Tissue Res. , 336, 287-97. PMID: 19255788 DOI.
- Lhuaire M, Tonnelet R, Renard Y, Piardi T, Sommacale D, Duparc F, Braun M & Labrousse M. (2015). Developmental anatomy of the liver from computerized three-dimensional reconstructions of four human embryos (from Carnegie stage 14 to 23). Ann. Anat. , 200, 105-13. PMID: 25866917 DOI.
- Vestentoft PS, Jelnes P, Hopkinson BM, Vainer B, Møllgård K, Quistorff B & Bisgaard HC. (2011). Three-dimensional reconstructions of intrahepatic bile duct tubulogenesis in human liver. BMC Dev. Biol. , 11, 56. PMID: 21943389 DOI.
- Bonczek O, Balcar VJ & Šerý O. (2017). PAX9 gene mutations and tooth agenesis: A review. Clin. Genet. , 92, 467-476. PMID: 28155232 DOI.
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Cite this page: Hill, M.A. (2019, February 18) Embryology BGDB Gastrointestinal - Late Embryo. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/BGDB_Gastrointestinal_-_Late_Embryo
- © Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G