title: Morphogenesis of the ultimobranchial body and its colonizing cells in the chick embryo.
abstract: The development of the ultimobranchial body and its colonizing cells was studied in chick embryos in Hamburger-Hamilton's stages 21 to 46. The most significant observations included the following: 1.-The ultimobranchial body is a separate morphological entity with particular characteristics distinguishing it from the fourth pharyngeal pouch in all developmental stages. 2.-The fifth pharyngeobranchial ducts disappear in Hamburger-Hamilton's stage 27. 3.-From Hamburger-Hamilton's stage 27 on, the left ultimobranchial body is in contact with the caudal end of the left parathyroid IV primordium. 4.-The group made up of the ultimobranchial body and its colonizing cells at no time fuses with the thyroid gland.
authors.affiliation: Departamento de Ciencias Morfológicas, Instituto F. Olóriz, Universidad de Granada.
authors.forename: J A
authors.initials: JA
authors.lastname: Merida-Velasco
authors.forename: J
authors.initials: J
authors.lastname: Espin-Ferra
authors.forename: R L
authors.initials: RL
authors.lastname: Valdecasas
authors.forename: J D
authors.initials: JD
authors.lastname: Garcia-Garcia
mesh_terms: D000818:Animals; D002642:Chick Embryo; D014460:Ultimobranchial Body / Q000033:anatomy & histology / Q000166:cytology / Q000196:embryology*