Embryonic hepatic bud formation.
This section of notes gives an overview of how the liver develops. Initially, the transverse septum (septum transversum) arises at an embryonic junctional site. The junctional region externally is where the ectoderm of the amnion meets the endoderm of the yolk sac. The junctional region internally is where the foregut meets the midgut. The mesenchymal structure of the transverse septum provides a support within which both blood vessels and the liver begin to form. Arises at embryonic junction (septum transversum): externally is where ectoderm of amnion meets endoderm of yolk sac and internally is where the foregut meets the midgut. Mesenchymal structure of transverse septum provides a support within which both blood vessels and liver begin to form in the underlying splanchnic mesoderm.
In the early embryo, the liver and heart grow rapidly forming obvious external swellings on the ventral embryo surface. The liver's initial embryonic function is mainly cardiovascular. Firstly, as a vascular connection between the developing placental vessels to the heart. Secondly, as a haemopoietic tissue where blood stem cells reside before bone marrow development.
See also liver histology showing both developmental and adult histology.
- Historic Embryology:1912 Liver | 2008 Liver
Some Recent Findings
Human Liver (week 8, GA week 10)
- The fate of the vitelline and umbilical veins during the development of the human liver "Differentiation of endodermal cells into hepatoblasts is well studied, but the remodeling of the vitelline and umbilical veins during liver development is less well understood. We compared human embryos between 3 and 10 weeks of development with pig and mouse embryos at comparable stages, . ...We found no evidence for large-scale fragmentation of embryonic veins as claimed by the 'vestigial' theory. Instead and in agreement with the 'lineage' theory, the vitelline and umbilical veins remained temporally identifiable inside the liver after being engulfed by hepatoblasts. In agreement with the 'hemodynamic' theory, the left-right shunts develop de novo."
- Three-dimensional reconstructions of intrahepatic bile duct tubulogenesis in human liver "Samples from human prenatal livers ranging from 7 weeks + 2 days to 15½ weeks post conception as well as adult normal and acetaminophen intoxicated liver were used. ....In the developing human liver, three-dimensional reconstructions using multiple marker proteins confirmed that the human intrahepatic biliary tree forms through several developmental stages involving an initial transition of primitive hepatocytes into cholangiocytes shaping the ductal plate followed by a process of maturation and remodeling where the intrahepatic biliary tree develops through an asymmetrical form of cholangiocyte tubulogenesis.
- Dynamic signaling network for the specification of embryonic pancreas and liver progenitors Studies of the formation of pancreas and liver progenitors have focused on individual inductive signals and cellular responses. Here, we investigated how bone morphogenetic protein, transforming growth factor-beta (TGFbeta), and fibroblast growth factor signaling pathways converge on the earliest genes that elicit pancreas and liver induction in mouse embryos. The inductive network was found to be dynamic; it changed within hours. Different signals functioned in parallel to induce different early genes, and two permutations of signals induced liver progenitor domains, which revealed flexibility in cell programming. Also, the specification of pancreas and liver progenitors was restricted by the TGFbeta pathway."
- Notch signaling controls liver development by regulating biliary differentiation "In the mammalian liver, bile is transported to the intestine through an intricate network of bile ducts. Notch signaling is required for normal duct formation, but its mode of action has been unclear. Here, we show in mice that bile ducts arise through a novel mechanism of tubulogenesis involving sequential radial differentiation. Notch signaling is activated in a subset of liver progenitor cells fated to become ductal cells, and pathway activation is necessary for biliary fate."
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Search term: Liver Embryology
<pubmed limit=5>Liver Embryology</pubmed>
Liver Development Stages
Cell lineage during hepatic development (red) from uncommitted endoderm to functional adult hepatocytes and biliary epithelium.
Human Embryonic Liver Development
|Carnegie stage 11
||hepatic diverticulum development (ductal plate)
||Carnegie stage 12
septum transversum forming liver stroma
hepatic diverticulum forming hepatic trabeculae
||Carnegie stage 13
||epithelial cord proliferation enmeshing stromal capillaries
||Carnegie stage 14
||hepatic gland and its vascular channels enlarge
hematopoietic function appeared
||Carnegie stage 18
||obturation due to epithelial proliferation
bile ducts became reorganized (continuity between liver cells and gut)
|Week 7 to 8
||Carnegie stage 18 to Carnegie stage 23
||biliary ductules developed in periportal connective tissue
produces ductal plates that receive biliary capillaries
|Human data, see also liver development in the rat embryonic period (Carnegie stages 15-23). (More? Detailed Timeline | Timeline human development)
Embryonic Liver Development Timeline
- Bile duct - primordial duct links primitive intestine and liver parenchyma. Thick-walled tube (95 µm diameter) small lumen (22 µm diameter).
- Gall bladder - elongated tube further dilated, thick wall (125 µm diameter) and a narrow lumen (43 µm diameter).
- Hepatic sinusoids - intra-hepatic vasculature present
- Three venous tributaries flow into the liver sinusoids - right and left placental vein and a single vitelline vein.
- Cords of liver cells fragmented by vascular network of hepatic sinusoids.
- Between pericardial cavity (top) and mesonephros (bottom).
- Upper pole of the liver lies close to the septum transversum and early ventricles.
- Liver occupies the majority of abdominal cavity.
- Bile duct (future common bile duct), and a common hepatic duct, in contact with liver parenchyma without penetration.
- Primordium of accessory bile tract is an elongated and fusiform gall bladder projecting forward and by a short cystic duct that opens into common bile duct.
- Bile duct empties into second part of duodenum on its posterior side.
- Portal system visible - portal vein (100 µm diameter) arises from connection of upper mesenteric vein then at region of hepatic hilum (285 µm) divides into portal branches.
- Left umbilical vein empties into anterior extremity of the left portal branch.
- Ductus venosus (80 µm) connects the initial portion of left portal vein to the inferior vena cava.
- Hepatic venous system 3 branches - left hepatic vein (120 µm in diameter), middle hepatic vein (220 µm in diameter) and right hepatic vein (160 µm in diameter). Flows into the sub-cardinal vein.
- Liver parenchyma has two anatomical lobes (right and left lobe), separated by anteroposterior plane formed by placental vein.
||Bile duct morphology as earlier stage. Common bile duct empties at the level of the proximal duodenum.
- Portal vein arises from joining of splenic vein and superior mesenteric vein. At the level of the hepatic hilum, portal vein divides into two branches, right portal branch (420 µm in diameter) and left portal branch (540 µm in diameter). Right portal branch gives rise to a thin branch to caudate lobe. Ventral branch gives rise to segmental portal veins (VIII and V). Dorsal branch gives rise to the segmental portal veins (VI and VII).
- Ductus venosus connects initial portion of left portal vein to inferior vena cava, just upstream from hepatic vein afferents.
- Hepatic venous system as for previous stage.
|Hepatic parenchyma a large rounded mass.
||Bile duct morphology as earlier stage.
- Portal venous system complete.
- Ductus venosus (40 µm) connects initial portion of portal vein to middle hepatic vein.
- hepatic venous system has changed very little from the previous stage. Three hepatic veins empty into inferior vena cava.
- Liver parenchyma roughly oval shape, 2 symmetrical hepatic lobes. The quadrate and caudate lobes are identifiable.
- Upper pole of the liver bounded above by diaphragm.
|Data from a recent human study|
Links: liver | Carnegie stage 14 | 18 | 21 | 23 | simple embryonic timeline | Timeline human development
- Size - the liver initially occupies the entire anterior body area.
- Hepatoblast - endoderm the bipotential progenitor for both hepatocytes and cholangiocytes.
- Vascular - mesoderm blood vessels enter the liver (3 systems: systemic, placental, vitelline)
- Sinusoids - first blood vessels from vessels in septum transversum mesenchyme. Initially continuous endothelium, become fenestrated in fetal period and reticular development ongoing.
Adult Liver Cells
- hepatocytes - form 80% of liver, functional cells
- cholangiocytes - epithelial cells that line the bile ducts
- stellate cells - mesenchymal cells in the space of Disse
- Kupffer cells - liver macrophage in the sinusoids
Human Liver Growth (weight grams)
- Differentiates to form the hepatic diverticulum and hepatic primordium, generates the gall bladder then divides into right and left hepatic (liver) buds.
- Three connecting stalks (cystic duct, hepatic ducts) which fuse to form bile duct.
Left Hepatic Bud
- left lobe, quadrate, caudate (both q and c anatomically Left)
- caudate lobe of human liver consists of 3 anatomical parts: Spiegel's lobe, caudate process, and paracaval portion.
Right Hepatic Bud
Liver Structural Origins
- Hepatic Buds - form hepatocytes, produce bile from week 13 (forms meconium of newborn)
- Vitelline Veins - form sinusoids
- Mesenchyme - form connective tissue and Kupffer cells
Function - Haemopoiesis
Embryonic liver also involved in blood formation, after the yolk sac and blood islands acting as a primary site.
Components of Liver Formation
Mouse liver development signaling.
- foregut-midgut junction
- septum transversum
- hepatic diverticulum
- hepatic primordium
- midgut region
- hindgut diverticulum (pocket)
Data from mouse 
Hepatoblasts - endoderm-derived cells can differentiate into either:
- hepatocytes - populate the bulk of the liver parenchyma.
- cholangiocytes - line the intrahepatic bile ducts.
- Links: Endoderm | Mouse Development
The images below link to larger cross-sections of the mid-embryonic period (end week 4) stage 13 embryo starting just above the level of the liver and then in sequence through the liver to the level of the stomach. Note the relative position of the liver with respect to the abdominal cavity, the gall bladder and the heart.
The transverse septum differentiates to form the hepatic diverticulum and the hepatic primordium, these two structures together will go on to form different components of the mature liver and gall bladder. At this stage large vascular channels can be seen coursing through the liver primordium.
- Links: Carnegie stage 13 - serial sections | Embryo Serial Sections | Embryo Carnegie stage 13 Movies
The images below link to larger cross-sections of the end of the embryonic period (week 8) stage 22 embryo starting just above the level of the liver and then in sequence through the entire liver. (Note the sections are viewed from below, LR axis is reversed)
The rapidly developing liver also forms a visible surface bulge on the embryo directly under the heart bulge. The liver now occupies the entire ventral body cavity with parts of the gastrointestinal tract and urinary system "embedded" within its structure. Note in this image the large central ductus venosus.
- Links: Carnegie stage 22 - serial sections | Embryo Serial Sections | Embryo Carnegie stage 22 Movies
Selected Stage 22 Images
||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
Paraffin-embedded sections of human embryonic liver at 9 weeks (GA 11 weeks).
- A - (Stain - Haematoxylin Eosin)
- B, C - Alpha-Fetoprotein (AFP)
- D, G - Cytokeratin 18 (CK18)
- E, H - Cytokeratin 19 (CK19)
- F, I - Cytokeratin 7 (CK7)
The ductal plate is a primitive biliary epithelium which develops in mesenchyme adjacent to portal vein branches (periportal hepatoblasts). During liver development it is extensively reorganised (ductal plate remodelling) within the developing liver to form the intrahepatic bile ducts (IHBD). If remodelling does not occur, leading to excess of embryonic bile duct structures in the portal tract, these developmental abnormalities are described as "ductal plate malformation" (DPM).
Cholangiocyte tubulogenesis: "ductal plate" stages -> "remodeling bile duct" stage -> "remodeled bile duct"
Cartoon model of bile duct formation.
Ductal Plate Malformations
- Interlobular bile ducts - autosomal recessive polycystic kidney disease
- Smaller interlobular ducts - von Meyenburg complexes
- Larger intrahepatic bile ducts - Caroli's disease
The epithelial cells that line the bile ducts are called cholangiocytes.
The pathway below describes the production and passage of bile for final excretion into the duodenum:
- hepatocytes produce bile
- secreted into bile canaliculi
- connected to intrahepatic bile ducts
- intrahepatic bile ducts connect to the hepatic duct
- then the cystic duct for storage in the gallbladder
- then the common bile duct into the duodenum
The term extrahepatic bile ducts (EHBDs) is used to describe the hepatic, cystic, and common bile ducts.
The developing bile ducts express VEGF while hepatoblasts express angiopoietin-1, these two signals are thought to regulate arterial vasculogenesis and remodeling of the hepatic artery respectively.
Liver Blood Flow
Dual blood supply of the liver merges upon entry into the liver lobule at the portal field.
- branches of the portal vein
- branches of the hepatic artery
The blood flows along the sinusoid and exits at the central vein.
Adult Liver sinusoid structure
These are the adult functional cells forming the majority of the liver (80% of the cells).
Many different functions including:
- Storage of substances including glucose (as glycogen), vitamin A (possibly in specialized adipocytes), vitamin B12, folic acid and iron.
- Lipid Turnover synthesis of plasmalipoproteins
- Plasma Protein Synthesis albumin, alpha and beta globulins, prothrombin, fibrinogen
- Metabolism fat soluble compounds (drugs, insecticides), steroid hormones turnover
- Secretion bile (about 1 litre/day)
Kupffer Cells are a population of tissue macrophages found in the lumen of hepatic sinusoids, their role is endocytic against blood-borne materials entering the liver.
Primordial (primitive) macrophages arise in the yolk sac and then differentiate into fetal macrophages, either of these enter the blood and migrate into the developing liver.
Kupffer Cells image
- Search PubMed: Kupffer cell development
Liver Associated Vessels
Liver ventral surface and associated veins (human embryo, 24-25 days, after His.)
- ductus venosus - shunts approximately half the umbilical vein blood flow directly to the inferior vena cava.
- portal vein - carries blood from the gastrointestinal tract and spleen to the liver.
- left umbilical vein - carries oxygenated blood from the placenta to the embryo/fetus.
- right umbilical vein - vessel degenerates leaving a single (left) umbilical vein.
- vena revehens - veins from the sinusoid vessels in the liver to the inferior vena cava, that later develop into the hepatic veins.
Adult Liver Transplants
The Liver Lobule
Histology-fetal liver HEx40
Histology-fetal liver x100
Adult liver Portal Triad
- Links: liver histology
Congenital absence of the portal vein (CAPV) - a rare abnormality where the intestinal and splenic venous drainage bypass the liver and drain directly into the systemic veins through various porto-systemic shunts.
- Links: Gastrointestinal Tract - Abnormalities
- ↑ Hikspoors JPJM, Peeters MMJP, Mekonen HK, Kruepunga N, Mommen GMC, Cornillie P, Köhler SE & Lamers WH. (2017). The fate of the vitelline and umbilical veins during the development of the human liver. J. Anat. , 231, 718-735. PMID: 28786203 DOI.
- ↑ 2.0 2.1 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.
- ↑ Wandzioch E & Zaret KS. (2009). Dynamic signaling network for the specification of embryonic pancreas and liver progenitors. Science , 324, 1707-10. PMID: 19556507 DOI.
- ↑ Zong Y, Panikkar A, Xu J, Antoniou A, Raynaud P, Lemaigre F & Stanger BZ. (2009). Notch signaling controls liver development by regulating biliary differentiation. Development , 136, 1727-39. PMID: 19369401 DOI.
- ↑ Zorn AM. (2008). Liver development. , , . PMID: 20614624 DOI. | online extract | PDF
- ↑ 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
- ↑ 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.
- ↑ Archie JG, Collins JS & Lebel RR. (2006). Quantitative standards for fetal and neonatal autopsy. Am. J. Clin. Pathol. , 126, 256-65. PMID: 16891202 DOI.
- ↑ Pauwelyn K, Roelandt P, Notelaers T, Sancho-Bru P, Fevery J & Verfaillie CM. (2011). Culture of mouse embryonic stem cells with serum but without exogenous growth factors is sufficient to generate functional hepatocyte-like cells. PLoS ONE , 6, e23096. PMID: 21829697 DOI.
- ↑ Kaufman and Bard, The Anatomical Basis of Mouse Development 1999 Academic Press
- ↑ Tzur G, Israel A, Levy A, Benjamin H, Meiri E, Shufaro Y, Meir K, Khvalevsky E, Spector Y, Rojansky N, Bentwich Z, Reubinoff BE & Galun E. (2009). Comprehensive gene and microRNA expression profiling reveals a role for microRNAs in human liver development. PLoS ONE , 4, e7511. PMID: 19841744 DOI.
- ↑ Crawford JM. (2002). Development of the intrahepatic biliary tree. Semin. Liver Dis. , 22, 213-26. PMID: 12360416 DOI.
- ↑ Naito M, Hasegawa G, Ebe Y & Yamamoto T. (2004). Differentiation and function of Kupffer cells. Med Electron Microsc , 37, 16-28. PMID: 15057601 DOI.
- ↑ Sharma R, Greenhough S, Medine CN & Hay DC. (2010). Three-dimensional culture of human embryonic stem cell derived hepatic endoderm and its role in bioartificial liver construction. J. Biomed. Biotechnol. , 2010, 236147. PMID: 20169088 DOI.
Zorn AM. (2008). Liver development. , , . PMID: 20614624 DOI. | online extract | PDF
Zaret KS. (2016). From Endoderm to Liver Bud: Paradigms of Cell Type Specification and Tissue Morphogenesis. Curr. Top. Dev. Biol. , 117, 647-69. PMID: 26970006 DOI.
Gordillo M, Evans T & Gouon-Evans V. (2015). Orchestrating liver development. Development , 142, 2094-108. PMID: 26081571 DOI.
Dixon LJ, Barnes M, Tang H, Pritchard MT & Nagy LE. (2013). Kupffer cells in the liver. Compr Physiol , 3, 785-97. PMID: 23720329 DOI.
Nakamura T, Sakai K, Nakamura T & Matsumoto K. (2011). Hepatocyte growth factor twenty years on: Much more than a growth factor. J. Gastroenterol. Hepatol. , 26 Suppl 1, 188-202. PMID: 21199531 DOI.
Ando H. (2010). Embryology of the biliary tract. Dig Surg , 27, 87-9. PMID: 20551648 DOI.
Kung JW, Currie IS, Forbes SJ & Ross JA. (2010). Liver development, regeneration, and carcinogenesis. J. Biomed. Biotechnol. , 2010, 984248. PMID: 20169172 DOI.
Si-Tayeb K, Lemaigre FP & Duncan SA. (2010). Organogenesis and development of the liver. Dev. Cell , 18, 175-89. PMID: 20159590 DOI.
Le Lay J & Kaestner KH. (2010). The Fox genes in the liver: from organogenesis to functional integration. Physiol. Rev. , 90, 1-22. PMID: 20086072 DOI.
Roskams T & Desmet V. (2008). Embryology of extra- and intrahepatic bile ducts, the ductal plate. Anat Rec (Hoboken) , 291, 628-35. PMID: 18484608 DOI.
Szpinda M, Paruszewska-Achtel M, Woźniak A, Mila-Kierzenkowska C, Elminowska-Wenda G, Dombek M, Szpinda A & Badura M. (2015). Volumetric Growth of the Liver in the Human Fetus: An Anatomical, Hydrostatic, and Statistical Study. Biomed Res Int , 2015, 858162. PMID: 26413551 DOI.
Cardinale V, Wang Y, Carpino G, Mendel G, Alpini G, Gaudio E, Reid LM & Alvaro D. (2012). The biliary tree--a reservoir of multipotent stem cells. Nat Rev Gastroenterol Hepatol , 9, 231-40. PMID: 22371217 DOI.
Friedman JR & Kaestner KH. (2011). On the origin of the liver. J. Clin. Invest. , 121, 4630-3. PMID: 22105167 DOI.
Carpentier R, Suñer RE, van Hul N, Kopp JL, Beaudry JB, Cordi S, Antoniou A, Raynaud P, Lepreux S, Jacquemin P, Leclercq IA, Sander M & Lemaigre FP. (2011). Embryonic ductal plate cells give rise to cholangiocytes, periportal hepatocytes, and adult liver progenitor cells. Gastroenterology , 141, 1432-8, 1438.e1-4. PMID: 21708104 DOI.
Mall FP. A study of the structural unit of the liver. (1906) Amer. J Anat. 5:227-308.
Search Bookshelf Liver Development
Search Pubmed Now: Liver Development | Embryonic Liver Development
Mall FP. A study of the structural unit of the liver. (1906) Amer. J Anat. 5:227-308.
Fig 6 human embryo 2.1 mm
Fig 7 human embryo 4.3 mm
Fig 8 human embryo 4.3 mm
Fig 9 human embryo 4.5 mm
Fig 10 human embryo 4.5 mm
Fig 12 human embryo 6.6 mm
Fig 21 human embryo 11 mm
Fig 22 human embryo 11 mm
Fig 23 human embryo 11 mm
Fig 24 human embryo 11 mm
Fig 25 human embryo 11 mm
Fig 26 human embryo 20 mm
Fig 27 human embryo 20 mm
Fig 28 human embryo 24 mm
Fig 29 model human embryo 24 mm
Fig 30 model human embryo 24 mm
|Gastrointestinal Tract Terms
- allantois - An extraembryonic membrane, endoderm in origin extension from the early hindgut, then cloaca into the connecting stalk of placental animals, connected to the superior end of developing bladder. In reptiles and birds, acts as a reservoir for wastes and mediates gas exchange. In mammals is associated/incorporated with connecting stalk/placental cord fetal-maternal interface.
- amnion - An extra-embryonic membrane, ectoderm and extraembryonic mesoderm in origin, also forms the innermost fetal membrane, that produces amniotic fluid. This fluid-filled sac initially lies above the trilaminar embryonic disc and with embryoic disc folding this sac is drawn ventrally to enclose (cover) the entire embryo, then fetus. The presence of this membrane led to the description of reptiles, bird, and mammals as amniotes.
- amniotic fluid - The fluid that fills amniotic cavity totally encloses and cushions the embryo. Amniotic fluid enters both the gastrointestinal and respiratory tract following rupture of the buccopharyngeal membrane. The late fetus swallows amniotic fluid.
- atresia - is an abnormal interruption of the tube lumen, the abnormality naming is based upon the anatomical location.
- buccal - (Latin, bucca = cheek) A term used to relate to the mouth (oral cavity).
- bile salts - Liver synthesized compounds derived from cholesterol that function postnatally in the small intestine to solubilize and absorb lipids, vitamins, and proteins. These compounds act as water-soluble amphipathic detergents. liver
- buccopharyngeal membrane - (oral membrane) (Latin, bucca = cheek) A membrane which forms the external upper membrane limit (cranial end) of the early gastrointestinal tract. This membrane develops during gastrulation by ectoderm and endoderm without a middle (intervening) layer of mesoderm. The membrane lies at the floor of the ventral depression (stomodeum) where the oral cavity will open and will breakdown to form the initial "oral opening" of the gastrointestinal tract. The equivilent membrane at the lower end of the gastrointestinal tract is the cloacal membrane.
- celiac artery - (celiac trunk) main blood supply to the foregut, excluding the pharynx, lower respiratory tract, and most of the oesophagus.
- 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. liver
- cloaca" - (cloacal cavity) The term describing the common cavity into which the intestinal, genital, and urinary tracts open in vertebrates. Located at the caudal end of the embryo it is located on the surface by the cloacal membrane. In many species this common cavity is later divided into a ventral urogenital region (urogenital sinus) and a dorsal gastrointestinal (rectal) region.
- cloacal membrane - Forms the external lower membrane limit (caudal end) of the early gastrointestinal tract (GIT). This membrane is formed during gastrulation by ectoderm and endoderm without a middle (intervening) layer of mesoderm. The membrane breaks down to form the initial "anal opening" of the gastrointestinal tract.
- coelomic cavity - (coelom) Term used to describe a space. There are extra-embryonic and intra-embryonic coeloms that form during vertebrate development. The single intra-embryonic coelom forms the 3 major body cavities: pleural cavity, pericardial cavity and peritoneal cavity.
- crypt of Lieberkühn - (intestinal gland, intestinal crypt) intestinal villi epithelia extend down into the lamina propria where they form crypts that are the source of epithelial stem cells and immune function.
- duplication - is an abnormal incomplete tube recanalization resulting in parallel lumens, this is really a specialized form of stenosis. (More? Image - small intestine duplication)
- esophageal - (oesophageal)
- foregut - first embryonic division of gastrointestinal tract extending from the oral (buccopharyngeal) membrane and contributing oesophagus, stomach, duodenum (to bile duct opening), liver, biliary apparatus (hepatic ducts, gallbladder, and bile duct), and pancreas. The forgut blood supply is the celiac artery (trunk) excluding the pharynx, lower respiratory tract, and most of the oesophagus.
- galactosemia - Metabolic abnormality where the simple sugar galactose (half of lactose, the sugar in milk) cannot be metabolised. People with galactosemia cannot tolerate any form of milk (human or animal). Detected by the Guthrie test.
- gastric transposition - clinical term for postnatal surgery treatment for esophageal atresia involving esophageal replacement. Typically performed on neonates between day 1 to 4. (More? gastrointestinal abnormalities | PMID 28658159
- gastrointestinal divisions - refers to the 3 embryonic divisions contributing the gastrointestinal tract: foregut, Midgut and hindgut.
- gastrula - (Greek, gastrula = little stomach) A stage of an animal embryo in which the three germ layers (endoderm/mesoderm/ectoderm) have just formed. All of these germ layers have contributions to the gastrointestinal tract.
- gastrulation - The process of differentiation forming a gastrula. Term means literally means "to form a gut" but is more in development, as this process converts the bilaminar embryo (epiblast/hypoblast) into the trilaminar embryo (endoderm/mesoderm/ectoderm) establishing the 3 germ layers that will form all the future tissues of the entire embryo. This process also establishes the the initial body axes. (More? gastrulation)
- Guthrie test - (heel prick) A neonatal blood screening test developed by Dr Robert Guthrie (1916-95) for determining a range of metabolic disorders and infections in the neonate. (More? Guthrie test)
- hindgut - final embryonic division of gastrointestinal tract extending to the cloacal membrane and contributing part of the transverse colon (left half to one third), descending colon, sigmoid colon, rectum, part of anal canal (superior), urinary epithelium (bladder and most urethra). The hindgut blood supply is the inferior mesenteric artery.
- inferior mesenteric artery - main blood supply to the hindgut
- intestinal perforation - gastrointestinal abnormality identified in neonates can be due to necrotizing enterocolitis, Hirschsprung’s disease or meconium ileus.
- intraembryonic coelom - The "horseshoe-shaped" space (cavity) that forms initially in the third week of development in the lateral plate mesoderm that will eventually form the 3 main body cavities: pericardial, pleural, peritoneal. The intraembryonic coelom communicates transiently with the extraembryonic coelom.
- meconium ileus intestine obstruction within the ileum due to abnormal meconium properties.
- mesentery - connects gastrointestinal tract to the posterior body wall and is a double layer of visceral peritoneum.
- mesothelium - The mesoderm derived epithelial covering of coelomic organs and also line their cavities.
- Midgut - middle embryonic division of gastrointestinal tract contributing the small intestine (including duodenum distal bile duct opening), cecum, appendix, ascending colon, and part of the transverse colon (right half to two thirds). The midgut blood supply is the superior mesenteric artery.
- neuralation - The general term used to describe the early formation of the nervous system. It is often used to describe the early events of differentiation of the central ectoderm region to form the neural plate, then neural groove, then neural tube. The nervous system includes the central nervous system (brain and spinal cord) from the neural tube and the peripheral nervous system (peripheral sensory and sympathetic ganglia) from neural crest. In humans, early neuralation begins in week 3 and continues through week 4.
- neural crest - region of cells at the edge of the neural plate that migrates throughout the embryo and contributes to many different tissues. In the gastrointestinal tract it contributes mainly the enteric nervous system within the wall of the gut responsible for peristalsis and secretion.
- peritoneal stomata - the main openings forming the pathways for drainage of intra-peritoneal fluid from the peritoneal cavity into the lymphatic system.
- pharynx - uppermost end of gastrointestinal and respiratory tract, in the embryo beginning at the buccopharyngeal membrane and forms a major arched cavity within the phrayngeal arches.
- recanalization - describes the process of a hollow structure becoming solid, then becoming hollow again. For example, this process occurs during GIT, auditory and renal system development.
- retroperitoneal - (retroperitoneum) is the anatomical space (sometimes a potential space) in the abdominal cavity behind (retro) the peritoneum. Developmentally parts of the GIT become secondarily retroperitoneal (part of duodenum, ascending and descending colon, pancreas)
- somitogenesis The process of segmentation of the paraxial mesoderm within the trilaminar embryo body to form pairs of somites, or balls of mesoderm. A somite is added either side of the notochord (axial mesoderm) to form a somite pair. The segmentation does not occur in the head region, and begins cranially (head end) and extends caudally (tailward) adding a somite pair at regular time intervals. The process is sequential and therefore used to stage the age of many different species embryos based upon the number visible somite pairs. In humans, the first somite pair appears at day 20 and adds caudally at 1 somite pair/4 hours (mouse 1 pair/90 min) until on average 44 pairs eventually form.
- splanchnic mesoderm - Gastrointestinal tract (endoderm) associated mesoderm formed by the separation of the lateral plate mesoderm into two separate components by a cavity, the intraembryonic coelom. Splanchnic mesoderm is the embryonic origin of the gastrointestinal tract connective tissue, smooth muscle, blood vessels and contribute to organ development (pancreas, spleen, liver). The intraembryonic coelom will form the three major body cavities including the space surrounding the gut, the peritoneal cavity. The other half of the lateral plate mesoderm (somatic mesoderm) is associated with the ectoderm of the body wall.
- stomodeum - (stomadeum, stomatodeum) A ventral surface depression on the early embryo head surrounding the buccopharyngeal membrane, which lies at the floor of this depression. This surface depression lies between the maxillary and mandibular components of the first pharyngeal arch.
- stenosis - abnormal a narrowing of the tube lumen, the abnormality naming is based upon the anatomical location.
- superior mesenteric artery - main blood supply to the Midgut.
- viscera - the internal organs in the main cavities of the body, especially those in the abdomen, for example the Template:Intestines.
- visceral peritoneum - covers the external surfaces of the intestinal tract and organs within the peritoneum. The other component (parietal peritoneum) lines the abdominal and pelvic cavity walls.
- yolk sac - An extraembryonic membrane which is endoderm origin and covered with extraembryonic mesoderm. Yolk sac lies outside the embryo connected initially by a yolk stalk to the midgut with which it is continuous with. The endodermal lining is continuous with the endoderm of the gastrointestinal tract. The extra-embryonic mesoderm differentiates to form both blood and blood vessels of the vitelline system. In reptiles and birds, the yolk sac has a function associated with nutrition. In mammals the yolk sac acts as a source of primordial germ cells and blood cells. Note that in early development (week 2) a structure called the "primitive yolk sac" forms from hypoblast, this is an entirely different structure.
- yolk stalk - (vitelline duct, omphalomesenteric duct, Latin, vitellus = yolk of an egg) The endodermal connection between the midgut and the yolk sac. See vitelline duct.
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Cite this page: Hill, M.A. (2020, April 4) Embryology Gastrointestinal Tract - Liver Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Gastrointestinal_Tract_-_Liver_Development
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- © Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G