title: Anatomy and development of the sinoatrial valves in the dogfish (Scyliorhinus canicula).
abstract: We describe the adult anatomy and the development of the cardiac sinoatrial valves in the dogfish (Scyliorhinus canicula).
  
  
  
  We use scanning electron microscopy, histological and histochemical techniques in 39 hearts from embryos and adult specimens.
  
  
  
  The sinoatrial valvular set of the adult dogfish is composed of two transverse valves laterally attached to the sinoatrial junction at their bases. Both valves are composed of two muscular layers, the sinusal and the atrial, whose histological features are similar to the cardiac wall which they face. Collagen bundles, elastic fibers and fibroblasts are present between the muscular layers. The extracellular matrix between the valvular layers also contains sulphated and non-sulphated glycosaminoglycans. The sinoatrial valves develop from two lateral infoldings of the cardiac wall. The left fold is deeper than the right, causing a shift of the sinoatrial communication to the right. The epicardium progressively covers the outer sinoatrial groove and the space between the folds becomes populated by mesenchymal cells. The posterior atrioventricular endocardial cushion is in contact with the base of the left fold until the embryo has about 40 mm TL.
  
  
  
  The sinoatrial valves, in the dogfish, develop from lateral infoldings of the cardiac wall. This origin results in histological and histochemical differences between the two muscular layers which constitute the valves of the adult. The comparison of the sinoatrial valve morphogenesis between the dogfish and some higher vertebrates suggests that the right sinoatrial valve, but not the left, is homologous throughout the vertebrate phylogeny.
authors.affiliation: Department of Animal Biology, Faculty of Science, University of Málaga, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Gallego
authors.forename: A C
authors.initials: AC
authors.lastname: Durán
authors.forename: A V
authors.initials: AV
authors.lastname: De Andrés
authors.forename: P
authors.initials: P
authors.lastname: Navarro
authors.forename: R
authors.initials: R
authors.lastname: Muñoz-Chápuli
mesh_terms: D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D004284:Dogfish / Q000033:anatomy & histology*; D006325:Heart Atria / Q000033:anatomy & histology* / Q000196:embryology / Q000648:ultrastructure; D006351:Heart Valves / Q000033:anatomy & histology* / Q000196:embryology / Q000648:ultrastructure; D006651:Histocytochemistry; D008855:Microscopy, Electron, Scanning; D013997:Time Factors; D014684:Venae Cavae / Q000033:anatomy & histology* / Q000196:embryology / Q000648:ultrastructure
chemical_list: D000110:Acetylcholinesterase