Aims A study was designed to evaluate the influence of head conformation on the course of the nasolacrimal drainage system (NDS) in 31 brachycephalic and 15 mesocephalic cats using computed tomography (CT), CT-dacryocystography and anatomical methods. Findings The higher the degree of brachycephalia, the more the facial bones and upper canine teeth are displaced dorsally (ie, the more pronounced the dorsorotation). Dorsorotation leads to abnormal dislocation of the ventral nasal concha and to almost horizontally rotated upper canine teeth, and thus a steeply oriented NDS. In severe brachycephalia the NDS is forced to pass below the canine tooth (adopt a V-shaped course) and the drainage function seems to be inefficient. Practical relevance The rotation of the upper canine teeth appears to provide a basis for classification of brachycephalia in cats. The authors recommend that breeders avoid breeding from individuals affected by this condition and to give preference to cats with longer facial bones.
The patella is a sesamoid bone that is found in most mammals and is regularly located in the insertion tendon of the quadriceps femoris muscle. Up to now, only a little has been known about the topography, structure and function of the patella in marsupials. Therefore the stifles of 61 marsupials of 30 different species were studied by radiography, necropsy and light microscopy. It was found that only the family of bandicoots (Peramelidae) possessed a typical patella. The other species revealed a patelloid consisting of fibrocartilage. The structure of the patelloid revealed common characteristic features in the following families of marsupials: (1) Dasyuridae, Phalangeridae. Pseudocheriidae, and Potoroidae; (2) Burramyidae; (3) Phascolarctidae, Vombatidae, and Dendrolagus; and (4) Superfamily Macropodoidea (except Dendrolagus and Potoroidae). Our results imply that the degree of differentiation in the fibrocartilage of the patelloid was strongly correlated to the mechanical forces acting on the patelloid which are a result of the specific kind of locomotion and the way of life. Generally the bony patella does not belong to the phylogenetic programme of the marsupials--with the exception of the bandicoots which are very closely related to the subclass of placental mammals (Eutheria).
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