2009 Lecture 9

From Embryology

Endoderm Development

Introduction

This lecture will cover the early development of the endoderm layer of the trilaminar embryo as it contributes to the lining, glands and organs of the gastrointestinal tract (GIT). Note that we will be returning later to discuss the gastrointestinal tract, associated organs and physical growth changes.

Gastrulation, or gut formation, was historically the easiest observable feature of frog development.During the 4th week the 3 distinct portions (fore-, mid- and hind-gut) extend the length of the embryo and will contribute different components of the GIT. The large mid-gut is generated by lateral embryonic folding which "pinches off" a pocket of the yolk sac, the 2 compartments continue to communicate through the vitelline duct. On this current page there is a brief developmental overview and stage 13/14 embryo overview. The oral cavity (mouth) is formed following breakdown of the buccopharyngeal membrane (=oropharyngeal) and contributed to mainly by the pharynx lying within the pharyngeal arches. The opening of the GIT means that it contains amniotic fluid, which is also swallowed later in development. From the oral cavity the next portion of the foregut is initially a single gastrointestinal (oesophagus) and respiratory (trachea) common tube, the pharynx which lies behind the heart. Note that the respiratory tract will also form from a ventral bud arising at this level.

Lecture Objectives

  • Understanding of germ layer contributions to the early gastrointestinal tract (GIT)
  • Understanding of the folding of the GIT
  • Understanding of three main GIT embryonic divisions
  • Understanding of associated organ development (liver, pancreas, spleen)
  • Brief understanding of mechanical changes (rotations) during GIT development
  • Brief understanding of gastrointestinal abnormalities


Textbook References

  • Human Embryology Larson Chapter 9 p229-260
  • The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Chapter 12 p271-302

Additional Textbooks

  • Before We Are Born (5th ed.) Moore and Persaud Chapter 13 p255-287
  • Essentials of Human Embryology Larson Chapter 9 p123-146
  • Human Embryology Fitzgerald and Fitzgerald Chapter 19,20 p119-123
  • Anatomy of the Human Body 1918 Henry Gray 2. The Digestive Apparatus

Folding

3 GIT divisions

Foregut

Midgut

Hindgut

UNSW Embryology Links

Links

  • Embryo Images by Drs. Kathleen K. Sulik and Peter R. Bream Jr. notes/images sections on Gut Development


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Cite this page: Hill, M.A. (2020, January 19) Embryology 2009 Lecture 9. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/2009_Lecture_9

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© Dr Mark Hill 2020, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G