Gastrointestinal Tract - Liver Development: Difference between revisions

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Revision as of 15:48, 22 August 2010

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Introduction

This section of notes gives an overview of how the liver develops. 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. This structure grows rapidly.

GIT Links: Introduction | Medicine Lecture | Science Lecture | endoderm | mouth | oesophagus | stomach | liver | gallbladder | Pancreas | intestine | mesentery | tongue | taste | enteric nervous system | Stage 13 | Stage 22 | gastrointestinal abnormalities | Movies | Postnatal | milk | tooth | salivary gland | BGD Lecture | BGD Practical | GIT Terms | Category:Gastrointestinal Tract
GIT Histology Links: Upper GIT | Salivary Gland | Smooth Muscle Histology | Liver | Gallbladder | Pancreas | Colon | Histology Stains | Histology | GIT Development
Historic Embryology - Gastrointestinal Tract  
1878 Alimentary Canal | 1882 The Organs of the Inner Germ-Layer The Alimentary Tube with its Appended Organs | 1884 Great omentum and transverse mesocolon | 1902 Meckel's diverticulum | 1902 The Organs of Digestion | 1903 Submaxillary Gland | 1906 Liver | 1907 Development of the Digestive System | 1907 Atlas | 1907 23 Somite Embryo | 1908 Liver | 1908 Liver and Vascular | 1910 Mucous membrane Oesophagus to Small Intestine | 1910 Large intestine and Vermiform process | 1911-13 Intestine and Peritoneum - Part 1 | Part 2 | Part 3 | Part 5 | Part 6 | 1912 Digestive Tract | 1912 Stomach | 1914 Digestive Tract | 1914 Intestines | 1914 Rectum | 1915 Pharynx | 1915 Intestinal Rotation | 1917 Entodermal Canal | 1918 Anatomy | 1921 Alimentary Tube | 1932 Gall Bladder | 1939 Alimentary Canal Looping | 1940 Duodenum anomalies | 2008 Liver | 2016 GIT Notes | Historic Disclaimer
Human Embryo: 1908 13-14 Somite Embryo | 1921 Liver Suspensory Ligament | 1926 22 Somite Embryo | 1907 23 Somite Embryo | 1937 25 Somite Embryo | 1914 27 Somite Embryo | 1914 Week 7 Embryo
Animal Development: 1913 Chicken | 1951 Frog

| original page

Liver Development Stages

Carnegie Stage
Feature
11
hepatic diverticulum development
12
cell differentiation

septum transversum forming liver stroma

hepatic diverticulum forming hepatic trabeculae

13
epithelial cord proliferation enmeshing stromal capillaries
14
hepatic gland and its vascular channels enlarge

hematopoietic function appeared

18
obturation due to epithelial proliferation

bile ducts became reorganized (continuity between liver cells and gut)

18 to 23
biliary ductules developed in periportal connective tissue

produces ductal plates that receive biliary capillaries

(More? Timeline human development)

Data from Godlewski G, etal.[1] "Stage 11 was characterized by hepatic diverticulum development, stage 12 and thereafter by cellular differentiation (septum transversum giving the liver stroma and hepatic diverticulum the hepatic trabeculae), and stage 13 by epithelial cord proliferation enmeshing stromal capillaries. From stage 14, the hepatic gland and its vascular channels presented considerable enlargement while hematopoietic function appeared. From this stage, the development of cystic primordium, never present in rat, was constant in man. At stage 18, after a period of obturation due to epithelial proliferation, the bile ducts became reorganized and ensured the continuity between liver cells and gut. From stages 18 to 23, biliary ductules developed in periportal connective tissue producing ductal plates that received biliary capillaries."

See also Liver development in the rat during the embryonic period (Carnegie stages 15-23).[2]

Components of Liver Formation

Primitive Endoderm

  • foregut diverticulum
  • foregut-midgut junction
    • septum transversum
      • hepatic diverticulum
        • cystic primordium
          • gall bladder
            • common bile duct
              • hepatic ducts
                • liver/gall bladder
      • hepatic primordium
        • hepatic parenchyma
          • hepatic sinusoids
            • lobes of liver
              • liver/gall bladder
  • midgut region
  • hindgut diverticulum (pocket)

Data from mouse [3]

Links: Endoderm | Mouse Development

Stage 13

stage 13 embryo

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.

Stage 13 (serial labeled images)
Stage 13 image 073.jpg Stage 13 image 074.jpg Stage 13 image 075.jpg Stage 13 image 076.jpg Stage 13 image 077.jpg Stage 13 image 078.jpg
D3L D4L D5L D6L D7L E1L
Stage 13 image 097.jpg Stage 13 image 098.jpg
G6L G7L
Links: Carnegie stage 13 - serial sections | Embryo Serial Sections | Flash movies | Quicktime movies

Stage 22

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.

Stage 22L serial labeled images
Stage 22 image 080.jpg Stage 22 image 081.jpg Stage 22 image 082.jpg Stage 22 image 083.jpg Stage 22 image 084.jpg
E3L E4L E5L E6L E7L
Stage 22 image 085.jpg Stage 22 image 086.jpg Stage 22 image 087.jpg Stage 22 image 088.jpg Stage 22 image 089.jpg
F1L F2L F3L F4L F5L
Links: Carnegie stage 22 - serial sections | Embryo Serial Sections | Flash movies | Quicktime movies

Selected Stage 22 Images

Stage 22 image 131.jpg 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.
Stage 22 image 181.jpg E4 Central veins of liver. Radiating appearance of hepatic sinusoids. unlabeled version
Stage 22 image 182.jpg E5 Central vein with endothelial lining, containing nucleated erythrocytes, fetal red blood cells. The fetal liver has an important haemopoietic role. unlabeled version

Ductal Plate

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).

Ductal Plate Malformations

  • Interlobular bile ducts - autosomal recessive polycystic kidney disease
  • Smaller interlobular ducts - von Meyenburg complexes
  • Larger intrahepatic bile ducts - Caroli's disease

Bile Secretion

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:

  1. hepatocytes produce bile
  2. secreted into bile canaliculi
  3. connected to intrahepatic bile ducts
  4. intrahepatic bile ducts connect to the hepatic duct
  5. then the cystic duct for storage in the gallbladder
  6. 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.[4]

Hepatocytes

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

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.[5]


Kupffer Cells(Image: Blue Histology)

Search PubMed Now: Kupffer cell development

Adult Liver Transplants

Approximately 6,000 liver transplant operations are performed in the United States (http://www.liverfoundation.org/education/info/transplant/) and about 600–700 in the UK every year (http://www.britishlivertrust.org.uk/home/the-liver/liver-transplantation/a-history-of-liver-transplantation-and-current-statistics.aspx). The main limitation on numbers are the availability of donor organs.[6]

Histology

The Liver Lobule

Liver animated cartoon.gif

References

  1. <pubmed>9407542</pubmed>
  2. <pubmed>9718390</pubmed>
  3. Kaufman and Bard, The Anatomical Basis of Mouse Development 1999 Academic Press
  4. <pubmed>12360416</pubmed>
  5. <pubmed>15057601</pubmed>
  6. <pubmed>20169088</pubmed>| PMC2821762


Reviews

Search Pubmed

Search Bookshelf Liver Development

Search Pubmed Now: Liver Development | Embryonic Liver Development


Glossary Links

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Cite this page: Hill, M.A. (2024, March 28) 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 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G