Hello, Lexearl! Apologies for my earlier post, as I have mistakenly placed the answer to a previous question. Please disregard it instead. To answer your question:
During embryonic development, the trachea and esophagus start forming as a single tube and the failure of the development of the tracheoesophageal septum results in tracheoesophageal fistula and esophageal atresia. While both abnormalities are associated with each other, it is important to note that esophageal atresia is a result of the failure of the primitive foregut to recanalize while tracheoesophageal fistula is the failure of the lung bud to completely separate from the foregut (Madanick & Kaila, 2002). With this information, two major points can be noted: (1) the formation of the lung bud precedes the development of the esophageal atresia and tracheoesophageal fistula; and (2) the lung bud does not develop into an esophageal atresia, rather the failed recanalization of the primitive foregut.
Furthermore, the outgrowth was dubbed as the lung bud even if there is a development of the esophageal atresia (and formation of tracheoesophageal fistula) because there is a theory stating that it is the respiratory diverticulum that fails to elongate which results in the failure of the trachea to grow while the lung bud may still develop normally. With this, the foregut’s overall elongation and growth continue with the bronchial structures that originated from the foregut. After some time, the foregut rostral to the bronchi will assume tracheal histological characteristics while the foregut distal to the bronchial origin connects to the stomach and is known as the fistula. The upper atretic esophagus, on the other hand, is a result of the rearrangement of the anterior foregut (Ioannides & Copp, 2009).
To answer the second question, the tracheoesophageal sulcus must take the form of a saddle-shaped fold as it is crucial to the formation of the tracheoesophageal septum and thus, to the normal separation of the esophagus and trachea. Catenoidal configurations also possess growth-limiting properties that aid in the correct alignment of the different components of a developing body organ. Hence, since the normal development of the tracheoesophageal septum is dependent in the saddle-shaped fold, tracheoesophageal malformations (e.g., esophageal atresia and tracheoesophageal fistula) can be attributed to any configurational abnormalities arising during the development of the embryo (Sutliff & Hutchins, 1994).
References
During embryonic development, the trachea and esophagus start forming as a single tube and the failure of the development of the tracheoesophageal septum results in tracheoesophageal fistula and esophageal atresia. While both abnormalities are associated with each other, it is important to note that esophageal atresia is a result of the failure of the primitive foregut to recanalize while tracheoesophageal fistula is the failure of the lung bud to completely separate from the foregut (Madanick & Kaila, 2002). With this information, two major points can be noted: (1) the formation of the lung bud precedes the development of the esophageal atresia and tracheoesophageal fistula; and (2) the lung bud does not develop into an esophageal atresia, rather the failed recanalization of the primitive foregut.
Furthermore, the outgrowth was dubbed as the lung bud even if there is a development of the esophageal atresia (and formation of tracheoesophageal fistula) because there is a theory stating that it is the respiratory diverticulum that fails to elongate which results in the failure of the trachea to grow while the lung bud may still develop normally. With this, the foregut’s overall elongation and growth continue with the bronchial structures that originated from the foregut. After some time, the foregut rostral to the bronchi will assume tracheal histological characteristics while the foregut distal to the bronchial origin connects to the stomach and is known as the fistula. The upper atretic esophagus, on the other hand, is a result of the rearrangement of the anterior foregut (Ioannides & Copp, 2009).
To answer the second question, the tracheoesophageal sulcus must take the form of a saddle-shaped fold as it is crucial to the formation of the tracheoesophageal septum and thus, to the normal separation of the esophagus and trachea. Catenoidal configurations also possess growth-limiting properties that aid in the correct alignment of the different components of a developing body organ. Hence, since the normal development of the tracheoesophageal septum is dependent in the saddle-shaped fold, tracheoesophageal malformations (e.g., esophageal atresia and tracheoesophageal fistula) can be attributed to any configurational abnormalities arising during the development of the embryo (Sutliff & Hutchins, 1994).
References
- Ioannides, A. S., & Copp, A. J. (2009). Embryology of oesophageal atresia. Seminars in pediatric surgery, 18(1), 2–11. https://doi.org/10.1053/j.sempedsurg.2008.10.002
- Madanick, R. D., & Kaila, V. (2002). Anatomy, histology, embryology, and developmental anomalies of the esophagus. Sleisenger & Fordtran's gastrointestinal and liver disease : pathophysiology, diagnosis, management. Philadelphia :Saunders.
- Sutliff, K. S., & Hutchins, G. M. (1994). Septation of the respiratory and digestive tracts in human embryos: crucial role of the tracheoesophageal sulcus. The Anatomical record, 238(2), 237–247. https://doi.org/10.1002/ar.1092380210