Gastrointestinal Embryology

Writer: Yazan AlHabil, M.D.

Keywords: Embryology, Primitive Gut Tube, Foregut, Midgut, Hindgut, Rotation, Mesenteries, Congenital Abdominal Wall Defects

Overview

The gastrointestinal (GI) tract originates from the primitive gut tube, a structure derived from the endodermal lining of the yolk sac during early embryogenesis. Through coordinated craniocaudal and lateral folding in the 4th week of development, the gut tube forms and differentiates into distinct segments. These segments—foregut, midgut, and hindgut—each have defined vascular and neural supplies and give rise to specific GI organs.

Primitive Gut Tube (4th Week of Development)

●        Formed from the endoderm of the yolk sac (Figure 1).

●        Result of embryonic folding in week 4.

●        Divides into three regions:

o    Foregut: supplied by the celiac trunk.

o    Midgut: supplied by the superior mesenteric artery (SMA).

o    Hindgut: supplied by the inferior mesenteric artery (IMA).

●        Surrounded by splanchnic mesoderm, which contributes to its muscle and connective tissue.

Figure 1. An illustration of the primitive gut.

Foregut, Midgut, and Hindgut Derivatives and Their Neurovascular Supply

Non-Gut Tube Derivatives

●        Buccopharyngeal membrane: future oral cavity.

●        Cloacal membrane: forms the anal canal distal to the pectinate line.

●        Dorsal mesentery: contributes to the spleen, dorsal pancreatic bud, gastrosplenic ligament, splenorenal ligament, and greater omentum.

●        Ventral mesentery: forms the liver, ventral pancreatic bud, falciform ligament, and lesser omentum.

●        Somatic mesoderm: gives rise to the parietal peritoneum.

●        Splanchnic mesoderm: forms the visceral peritoneum.

Germ Layers of the GI Tract

NOTE: The spleen is mesodermal in origin, despite its proximity to foregut structures.

Figure 2. The germ layers of the GI tract.

OpenStax. (2013). Fate of germ layers in embryo [Illustration]. In Anatomy and Physiology (Fig. 28.10, p. 1342). OpenStax. https://openstax.org/details/books/anatomy-and-physiology

Image retrieved from Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Fate_of_germ_layers_of_the_embryo.png

Rotation of the Stomach (Foregut Rotation)

●        Occurs between weeks 4–6.

●        Rotates 90° clockwise along its longitudinal axis.

●        Results in:

o    Lesser curvature on the right (anterior).

o    Greater curvature on the left (posterior).

o    Left vagus nerve becomes anterior to the stomach.

o    Right vagus nerve becomes posterior.

o    Liver and duodenum shift to the right.

o    Spleen and pancreas move to the left.

Rotation of the Midgut (Intestinal Rotation)

Figure 3. Rotation of the midgut around the SMA.

(A) Formation of a hairpin loop around the superior mesenteric artery around fifth week. (B) Herniation of the midgut into the umbilicus around sixth week, and rotation 90 degrees counterclockwise around the superior mesenteric artery, (C) Return of the intestines into the abdomen around 10th week, (D) Further rotation of the intestines within the abdominal cavity around 11th week, so that the cecum is positioned in the right upper quadrant, (E) Fixation of the cecum in the right lower quadrant, thus completing intestinal rotation (270 degrees total).

Danowitz, M., & Solounias, N. (2016). Rotation of the midgut around the superior mesenteric artery [Illustration]. In Embryology, comparative anatomy, and congenital malformations of the gastrointestinal tract. Edorium Journal of Anatomy and Embryology, 3, 39–50. https://doi.org/10.5348/A04-2016-14-RA-6

Image retrieved from Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Rotation_of_the_midgut_around_the_superior_mesenteric_artery.png

Congenital Malformations of the Anterior Abdominal Wall

Figure 4. An illustration of omphalocele.

Centers for Disease Control and Prevention, National Center on Birth Defects and Developmental Disabilities. (2012, December 11). Omphalocele drawing [Illustration]. Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Omphalocele-drawing.jpg

Figure 5. An illustration of gastroschisis.

Centers for Disease Control and Prevention. (2013, November 10). Illustration of a baby with gastroschisis [Illustration]. Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Gastroschisis-web.jpg

Figure 6. A photograph of a patient with congenital umbilical hernia.

Jpogi. (2009, December 31). Umbilical hernia in a 6-week-old infant [Photograph]. Wikimedia Commons. https://commons.wikimedia.org/wiki/File:Umbilical_Hernia.JPG