This current page contains GIT Practical will link to information about GIT organ development. You do not need this information to complete the Practical class.
This page is currently only a template.
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.
Liver Bud
Differentiates to form the hepatic diverticulum and hepatic primordium, generates the gall bladder then divides into right and left hepatic buds.
Three connecting stalks (cystic duct, hepatic ducts) which fuse to form bile duct.
Hepatic Bud
Left Hepatic Bud- left lobe, quadrate, caudate (both q and c anatomically Left)
Right Hepatic Bud- right lobe
Function - Haemopoiesis
Embryonic liver also involved in blood formation, after the yolk sac and blood islands acting as a primary site.
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
(More? GIT Notes - Liver Development)
Spleen arises in week 5 within dorsal mesogastrium as proliferating mesenchyme.
Hemopoietic function (like the liver) cells arise from yolk sac wall. Spleen generates both red and white cells in the 2nd trimester.
Note that embryonic RBCs remain nucleated.
(More? GIT Notes - Spleen Development)
At the foregut/midgut junction the septum transversum generates 2 pancreatic buds (dorsal and ventral endoderm) which will fuse to form the pancreas. The dorsal bud arises first and generates most of the pancreas. Differentiates to establish specific cells for endocrine and exocrine function.
In the fetal period islet cell clusters (icc) differentiate from pancratic bud endoderm. These cell clusters form acini and ducts (exocrine). On the edge of these cell clusters pancreatic islets (endocrine) also form.
The pancreas exocrine function begins after birth, while the endocrine function (hormone release) can be measured from 10 to 15 weeks onward. At this stage, it is not clear what the exact roles of these hormones are in regulating fetal growth.
(More? GIT Notes - Pancreas Development)
UNSW Embryology
General Notes on Gastrointestinal Tract Development
Embryo Images by Drs. Kathleen K. Sulik and Peter R. Bream Jr.
Seven linked notes/images sections on Gut Development
Developmental Biology. 6th ed. Gilbert, Scott F. Sunderland (MA): Sinauer Associates, Inc.; c2000
This textbook covers developmentnot only in humans but other species including plants. As such, some of the material will not be directly relevant to human development, but should be used comparatively or as a model. The entire text and images is available free online from the NCBI Bookshelf. You can either click the provided links or do your own search using the search link.
Molecular Biology of the Cell 4th ed. Alberts, Bruce; Bray, Dennis; Lewis, Julian; Raff, Martin; Roberts, Keith; Watson, James D. New York and London: Garland Publishing; c2002. The entire text and images is available free online from the NCBI Bookshelf. You can either click the provided links or do your own search using the search link.
GIT References This page contains links to selected Gastrointestinal Tract references from National Library of Medicine PubMed and other sources. There are also links to pages on specific topics and a search window for entering your own term and carrying out a database search.
In general, these scientific review papers are in significantly more detail than you either require or understand at this stage. These papers do though give an overview/idea of our current understanding of GIT developmental mechanisms. No harm in having a look.......
This database is probably a bit advanced to use at this stage, but as your knowledge grows, should be an ongoing invaluable resource to give a medical "snapshot" of a genetic disorder or topic.
Try a search of the database with a keyword from this current practical or a specific genetic disease.
This excellent resource is provided by the National Library of Medicine (NLM), National Center for Biological Information (NCBI) website. The NCBI site in addition to having key databases for genomic and molecular biology research, and PubMed literature database, has setup a Bookshelf providing free online full cross-referenced and searchable textbooks. The OMIM resource (above) is also located within the NCBI website.
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Link to First page in this GIT Practical - GIT |
Use the alphabetical list below to find definitions of terms that are new to you or use the Google search window to search UNSW Embryology site.
A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W |X | Y | Z |
accessory pancreatic duct - (APD) This duct also called Santorini’s duct may be present as an anatomical variation due to the embryological origin of the pancreas from two pancreatic buds (dorsal and ventral). Note the main pancreatic duct (MPD) from the dorsal bud, present in the body and tail of the pancreas (also called Wirsung’s duct). (More? Pancreas | Pancreas History)
cholangiocyte - Bile duct epithelial cell derived from hepatoblasts during embryonic liver development. These cells line the bile duct system and have apical cilia. Cholangiocytes function (mechano-, osmo-, and chemo-sensory) to regulate the fluidity and alkalinity of canalicular bile by reabsorptive and secretory events adjusting the final secreted bile composition. Abnormalities associated with these cells development or function are called cholangiociliopathies (polycystin-1, polycystin-2, and fibrocystin). (More? Gastrointestinal Tract - Liver)
ductus venosus - The vitelline blood vessel lying within the liver that connects (shunts) the portal and umbilical veins to the inferior vena cava and also acts to protect the fetus from placental overcirculation. Absence can cause hydrops fetalis and the umbilical vein then drains directly into the inferior vena cava or right atrium. Postnatally this shunt functionally closes then structurally closes and degenerates to form it the ligamentum venosum. (More? Cardiovascular Notes)
falciform ligament - A sheet of parietal peritoneum between the two principal lobes of the liver. The ligamentum teres, the remnant of umbilical vein, lies within its folds. (More? GIT Notes | Liver)
intrahepatic bile ducts - (IHBDs) transport bile secreted from hepatocytes to the hepatic duct. The cells that line the IHBD are biliary epithelial cells generated from bipotent hepatoblasts around the portal vein. (More? GIT Notes - Liver | GIT Notes - Gall Bladder)
maternal passive immunity - Term used to describe the transfer of maternal antibodies to the fetus (through the placenta) and the neonate (through milk). (More? Placenta | Normal Development - Milk)
meconium The gastrointestinal contents that accumulate in the intestines during the fetal period. This material is a mixture of liver bile and glandular secretions, amniotic fluid, and cellular debris. Meconium is also used to describe the first postnatal rectal discharge from the neonate. Fetal stress in the third trimester or at parturition can lead to premature meconium discharge, into the amniotic fluid and ingestion by the fetus (meconium aspiration syndrome) and damage to respiratory function. Damage to placental vessels meconium myonecrosis may also occur. (More? Birth | Gastrointestinal Tract Notes | Respiratory Notes)
meconium aspiration syndrome (MAS) Fetal stress in the third trimester, prior to/at/ or during parturition can lead to premature meconium discharge into the amniotic fluid and sunsequent ingestion by the fetus and damage to respiratory function. Damage to placental vessels meconium myonecrosis may also occur.
Home Page
Embryo stages
Fetal Dev
Dev Notes 1
Dev Notes 2
System Notes
Acknowledgements
Practical GIT
Introduction
1. Trilaminar Embryo
2. Folding
3. Early Embryo
4. Late Embryo
5. Fetal
6. Postnatal
Background
Online Refs
GIT- Histology
GIT- Organs
GIT- Abnormalities
Movies
News
Class Notes
Serial Images
K12 Students
Abnormal
Histology
Site Map
School of Med Sci
UNSW Medicine
University of NSW
UNSW Cell Biology
NCBI Books
Dev Biol (Gilbert)
Look at these resources in your own time!
Use this page to view linked Online textbooks from NLM as background to this practical. For additional detailed/specific research references, use the righthand link to PubMed results. In most cases, unless it is a review article, these references are probably too detailed for this current level of study.
There are several excellent textbooks (by Larsen, Moore and Persaud, Carlsson, Langman, Gilbert and Sunderland to name a few) that alone would be sufficient for your coverage of this entire topic. Some of which have some online content.
Until we have easy to read PDAs, do not discount the value of being able to read a book anywhere and anytime.
In addition, there are a growing number of excellent online texts. The advantage of these online resources is mainly their searchability and cross referenced links. The second advantage should be the availability of multimedia (animations, movies etc). This multimedia is particularly valuable in Embryology when everything is so small and inaccessible, but unfortunately there are currently very few multimedia resources yet developed. I have a small number of UNSW Embryology animations and movies that you should look at, in particular those based on Larsen's textbook.
Please email Dr Mark Hill if you wish to make a comment about this current project.