title: Development of external genitalia in fetal and neonatal domestic cats.
abstract: Development of the external genitalia of fetal and neonatal cat were studied macroscopically, paying attention to the formation of the labia and the sexual differentiation. The female urogenital folds budded from each side of the genital tubercle and, gradually extended to the tip of the genital tubercle by the 6.8 cm stage in crown-rump length. Then, the well-developed urogenital folds ensheathed completely the genital tubercle to form the prepuce of clitoris and the labia, flanking the external opening of vagina as the folds of skin which were equivalent to the labia minora in humans. The genital swellings known to become the labia majora in humans were clearly recognized in the caudolateral region of the genital tubercle during the fetal stage. These swellings became flat and obscure after birth. Thus, in cats the genital swellings did not join to the formation of the labia in the same way as in humans. The sex difference in the external genitalia was first observed at the 3.2-3.3 cm stages. In the male, the anogenital raphe appeared and the caudal portion of the genital swellings moved and fused each other at the caudal region of the genital tubercle. In the female, both features were not easy to observe.
authors.affiliation: Department of Laboratory Animal, School of Veterinary Medicine, Azabu University, Sagamihara, Kanagawa, Japan. inomata@azabu-u.ac.jp
authors.forename: Tomo
authors.initials: T
authors.lastname: Inomata
authors.forename: Makoto
authors.initials: M
authors.lastname: Ariga
authors.forename: Katsuyasu
authors.initials: K
authors.lastname: Sakita
authors.forename: Naomi
authors.initials: N
authors.lastname: Kashiwazaki
authors.forename: Junya
authors.initials: J
authors.lastname: Ito
authors.forename: Kiyofumi
authors.initials: K
authors.lastname: Yokoh
authors.forename: Masahiko
authors.initials: M
authors.lastname: Ichikawa
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Ninomiya
authors.forename: Seiya
authors.initials: S
authors.lastname: Inoue
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002415:Cats / Q000196:embryology*; D018568:Crown-Rump Length; D005260:Female; D005835:Genitalia / Q000196:embryology*; D005865:Gestational Age; D008297:Male; D012727:Sex Characteristics; D012733:Sex Differentiation / Q000502:physiology*; D014844:Vulva / Q000196:embryology*