BGDB Gastrointestinal - Activity 1

Learning Activity 1

1. Identify the different contributions of the trilaminar embryo to the formation of the gastrointestinal tract (GIT).
2. Describe the development and folding of the yolk sac and endoderm.
3. List the adult structures developed from the foregut, midgut and hindgut. 


1. Trilaminar Embryo Contributions

The gastrointestinal tract has contributions from all 3 germ layers (ectoderm, mesoderm and endoderm). Identify the specific components that each germ layer contributes to the tract. We will discuss the associated organs later in Activity 3.

File:Trilaminar embryo.jpg

File:Endoderm cartoon.jpg

File:Mesoderm-cartoon4.jpg

2. Folding

In week 3 to 4 (GA week 5 and 6) folding of the entire embryonic disc occurs ventrally. The notochord forms a midline rod-like region running rostro-caudally.

Watch the two animations below and discuss the GIT folding that is occurring within the embryo.

<html5media height="360" width="360">File:Endoderm 003.mp4</html5media> Click Here to play on mobile device	<html5media height="540" width="390">File:Week3_folding.mp4</html5media> Click Here to play on mobile device
Page | Play	Page | Play

In relation to the notochord:

• Laterally (either side of the notochord) lies mesoderm.
• Rostrally (above the notochord end) lies the buccopharyngeal membrane, above this again is the mesoderm region forming the heart.
• Caudally (below the notochord end) lies the primitive streak (where gastrulation occurred), below this again is the cloacal membrane.
• Dorsally (above the notochord) lies the neural tube then ectoderm.
• Ventrally (beneath the notochord) lies the mesoderm then endoderm.

Folding of the embryonic disc "pinches off" part of the yolk sac forming the first primitive GIT.

3. Gut Parts

Interactive component

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BGDB: Lecture - Gastrointestinal System | Practical - Gastrointestinal System | Lecture - Face and Ear | Practical - Face and Ear | Lecture - Endocrine | Lecture - Sexual Differentiation | Practical - Sexual Differentiation | Tutorial

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Cite this page: Hill, M.A. (2024, May 17) Embryology BGDB Gastrointestinal - Activity 1. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/BGDB_Gastrointestinal_-_Activity_1

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G