Anatomical Notes on the Course of the Esophagus in Thoracic Cavity in Bovine Fetuses and Neonates Based on Observation of Resin-Casts of Thoracic Hollow Organs

Abstract

The thoracic course of the esophagus of bovine fetuses and neonates was examined by resin-casts of the thoracic hollow organs with a comparison of the formalin-hardened organs, with special reference to the site of constriction, curvature and ampulla. Resin and formalin injections were made into the esophagus, and trachea and the axillary artery and vein. The esophagus in the thorax had three constrictions. The first was located at the site pressed by the dorso-caudal end of the developing thymus and by the anterior border of the left anterior pulmonary lobe. The second was located at the site where the aortic arch was attached on its left side, just before the bifurcation of the trachea. The third was located very closely to the hiatus esophageus of the diaphragm, surrounded by the left and right posterior and the accessory pulmonary lobes and the muscular diaphragmatic crura which were well-developed characteristically in this species. The esophagus in the thorax had three curvatures. The first was concave ventrally, located between the level of the seventh cervical vertebra and that of the second thoracic vertebra. The second curvature was convex dorsally, beginning at the site of the attachment of the aorta to bend slightly ventro-caudad. The third was horizontal, beginning shortly behind the bifurcation of the trachea in the median plane of the body axis to bend gently toward the left-biased hiatus esophageus. The esophagus had an ampulla in the way of passing the posterior mediastenum.