ABSTRACT
The human respiratory system begins to form about day 26-27 after fertilization. It is first indicated by a median laryngotracheal groove in the caudal and ventral wall of pharynx. The endoderm which lines the laryngotracheal groove gives rise of the epithelium and glands of the larynx, trachea, bronchi and the pulmonary lining epithelium. The connective tissue, the cartilage and the smooth muscle of these structures develop from the splanchnic mesoderm surrounding the forgut. In studying the development of the respiratory system at the Department of Anatomy, Siriraj Hospital medical students should trace the serial section of 10 mm. pig embryos. In doing this, they will be able to observe the laryngotracheal groove at the floor of the pharynx and when tracing the sections caudally, they will be able to observe the trachea, esophagus and the bifurcation of the trachea forming primary bronchi as well as smaller of branches of present study attempts to show the development of respiratory system of rabbit embryos in order to find the most suitable for use for as a laboratory model for medical students, embryological studies. A 10mm. rabbit embryo can be used instead of a pig embryo for studying the development of the respiratory system, as nowadays pig embryos are not available.