The gastrointestinal tract is a tube that extends from the end of the pharynx to the anus. Its functions are the propulsion and digestion of food and the elimination of the waste products. It is divided into primary segments that are, from rostral to caudal, the esophagus, stomach, small intestine, and large intestine. The primary segments are divided into secondary segments and are, from rostral to caudal: the proximal, middle and distal parts of the esophagus; the cardia, fundus, body, and antrum or pylorus of the stomach; the duodenum (with its first, second, third, and fourth parts), jejunum and ileum of the small intestine; and the cecum, appendix, ascending, transverse, descending, sigmoid, rectum, and anal canal segments of the large intestine. The histologic junctions between the primary segments may be abrupt but those between the secondary segments are gradual transition zones. Sphincters and valves at junctions of primary segments regulate forward propulsion and prevent retrograde flow of the contents. Although the general architecture of the gastrointestinal tract is established in embryonic life, there is continued development of the layers of the wall during fetal life. Thus, the histology of the gastrointestinal tract is characterized by numerous changes in the fetal period, which are highlighted in this chapter.
KeywordsGerminal Luminal Crest Mast Esophagitis
The author thanks Dr. Tricia R. Bhatti from The Children’s Hospital of Philadelphia, Philadelphia, PA, for invaluable assistance in selecting microscopic slides for photography, taking photographs, and editing the manuscript.
- 2.Lewis F: The early development of the entodermal tract and the formation of its subdivisions. In Human Embryology. Edited by Keibel F, Mall FP. Philadelphia: J. B. Lippincott; 1912:295–334.Google Scholar
- 3.O’Rahilly R, Muller F: Developmental Stages In Human Embryos. Washington DC: The Carnegie Institution of Washington; 1987.Google Scholar
- 4.Sembra R, Tanaka O, Tanimura T: The digestive tract. In Atlas of Prenatal Histology. Edited by Nishimura H. Tokyo: Igaku-Shoin; 1983:193–225.Google Scholar
- 7.Lewis F: The development of the esophagus. In Human Embryology. Edited by Keibel F, Mall FP. Philadelphia: J. B. Lippincott; 1912:355–368.Google Scholar
- 8.Lewis F: Development of the stomach. In Human Embryology. Edited by Keibel F, Mall FP. Philadelphia: J. B. Lippincott; 1912:368–381.Google Scholar
- 9.Lewis F: Development of the small intestine. In Human Embryology. Edited by Keibel F, Mall FP. Philadelphia: J. B. Lippincott Company; 1912:381–393.Google Scholar
- 10.Lewis F: Development of the large intestine. In Human Embryology. Edited by Keibel F, Mall FP. Philadelphia: J. B. Lippincott Company; 1912:393–399.Google Scholar
- 12.O’Rahilly R, Muller F: Human Embryology & Teratology, edn 3. New York: Wiley-Liss; 2001.Google Scholar