title: Development of respiratory tract from bovine embryos.
abstract: We studied the development of respiratory tract in bovine embryos by light microscopy and transmission electronic microscopy. This process was observed formation of laryngeal-tracheal tube in embryos that present crown-rump (CR) length of 9.0 mm (20/21 days of pregnancy) at around the fourth gestational week; the organ wall appears to be formed of epithelium comprising several cell layers and supported by mesenchyme. Within the lungs, the areas subjacent to epithelium present condensed mesenchyme, while more distal areas loose mesenchyme, in which blood vessels beginn to form, as the organ is in a pseudo-glandular phase. Ultra-structurally, the mesenchyme cells present irregular shapes, having a stellar or fusiform appearance and are united by desmosomes, where the cytoskeleton attaches to the cellular membrane, forming a connection. The bifurcation of trachea caudal portion in the main bronchia is simultaneous to the appearance of the tracheal bronchi, during the fifth gestational week.
authors: Department of Surgery, School of Veterinary Medicine, Section of Domestic and Wild Animals Anatomy, Av Prof Orlando Marques de Paiva 87, São Paulo, SP 05508-270, Brazil.
authors: Miryan Lança Vilia
authors: ML
authors: Alberto
authors: Alvaro Carlos
authors: AC
authors: Galdos-Riveros
authors: Alicia Greyce Turatti
authors: AG
authors: Pessolato
authors: Jose Manoel
authors: JM
authors: dos Santos
authors: Maria Angélica
authors: MA
authors: Miglino
mesh_terms: D000818:Animals; D002417:Cattle / Q000196:embryology*; D012137:Respiratory System / Q000196:embryology* / Q000648:ultrastructure