Embryology, Gastrointestinal

Excerpt

The purpose of this article is to give an introduction of the gastrointestinal system, provide an outline of basic embryology, summarize the embryological events that take place with the gastrointestinal tract, and finally provide specific tests that can be utilized to detect GI anomalies.

The gastrointestinal (GI) system involves three germinal layers: mesoderm, endoderm, ectoderm.

1. Mesoderm gives rise to the connective tissue, including the wall of the gut tube and the smooth muscle.

2. Endoderm is the source of the epithelial lining of the gastrointestinal tract, liver, gallbladder, pancreas.

3. Ectoderm further separates into the surface ectoderm, neural tube, and neural crest. The surface ectoderm is the precursor to the epidermis, lens of eyes, nails, hair. The neural tube differentiates into the brain and spinal cord. The neural crest is the source of the peripheral nervous system, including the neurons of the GI tract (also called the enteric nervous system).

The gastrointestinal system has the divisions: the foregut, midgut, and hindgut. The foregut (or anterior gut) is from the oral cavity to the initial part of the duodenum. The midgut is from the mid-duodenum to the initial two-thirds of the transverse colon. The hindgut is from the later one-third transverse colon to the upper portion of the anus. The three sections of the GI tract have different blood supplies; the foregut receives vascular supply by the celiac artery, the superior mesentery artery supplies the midgut, and the hindgut gets its supply from the inferior mesentery artery.