Morphology and Classification of Right Ventricular Bands in the Domestic Dog (Canis familiaris).

Ventricular bands, also designated as 'false tendons', are described as single or multiple strands that cross the ventricles and have no connection to valvular cusps. Previous work indicates these strands are present in the ventricles of humans and some animal hearts and not always associated with cardiac pathologies. Despite these previous studies, the published literature is limited in documenting the morphology of these strands and incidence in animals. In this study, examination of 89 hearts showed six types of ventricular bands in the right ventricle of the domestic dog. These bands were classified according to their prevalence and points of attachment. Type I extended from the interventricular septum to the ventricular free wall, type II connected a musculus papillaris parvus to the ventricular free wall and type III connected trabeculae carneae on the interventricular septum. Type IV connected the trabeculae carneae on the ventricular free wall, type V interconnected papillary muscles and type VI connected the interventricular septum to a papillary muscle. While the study of these ventricular bands provided additional information on the cardiac anatomy of the domestic dog, it also showed their clinical importance. Several studies have proposed that their position in the ventricle may interfere with cardiac catheterization and pacemaker lead placement or be misinterpreted during echocardiography.

Atypical Chordae Tendineae of the Canine (Canis familiaris) Right Atrioventricular Valve.

The canine right atrioventricular valve cusps are anchored to papillary muscles by chordae tendineae. During ventricular systole, these tendineae keep the cusps from being pushed into the atrium. While this is the general description for chordae tendineae, several researchers have briefly documented chordae tendineae in animal and human hearts that do not attach to papillary muscles. In the 39 canine hearts examined, atypical chordae tendineae were observed in two hearts. In both dogs, a single stranded chordae tendineae extended from the free edge of the parietal cusp of the right atrioventricular valve to the ventricular free wall. While the discovery of these atypical tendineae provides additional information on canine cardiac anatomy, their presence may also be clinically significant. A review of the veterinary and biomedical literature showed entanglement in normal chordae tendineae can be a complication during cardiac catheterization or pacemaker lead placement. Given this issue with normal chordae tendineae, it seems logical to propose that these atypical tendineae could also cause catheter or pacemaker lead entanglement and therefore warrant further study and documentation.

Morphological Variations in the Canine (Canis familiaris) Right Ventricle Trabecula Septomarginalis Dextra and a Proposed Classification Scheme.

The trabecula septomarginalis dextra is a structure routinely mentioned in veterinary anatomy. While there are several studies on the morphology of this structure in select animal species, there are some characteristics that are not adequately described. The purpose of this study was to describe and classify this trabecula in the domestic dog using the number of branches that insert onto the ventricular free wall. In the 39 examined hearts, 17.95% were single stranded (type I) and 2.56% were y-shaped (IA). Then, 28.21% were web-like with 3 to 4 points of insertion (IB) and 51.28% were web-like with 5 or more points of insertion (IC). While the purpose of this study was to describe the morphology of this trabecula, it also showed there is variability in this structure within the same species. This undocumented variability could present a problem to researchers who use dogs as an animal model when testing catheters for invasive cardiac monitoring or cardiac stem cell therapy. Also a web-like trabecula could create problems during pacemaker lead placement for the treatment of symptomatic bradycardia because of the potential for catheter entanglement in these branches.

Microscopic anatomy of the lower respiratory tract of the grey short-tailed opossum (Monodelphis domestica).

The respiratory tracts of seven grey short-tailed opossums were histologically examined. Six opossums were prepared by perfusion with buffered formalin. Opossum seven was perfused with gluteraldehyde. Samples taken from the respiratory passages and lungs of specimens 1-6 were stained with haematoxylin and eosin. A mixture of methylene and azure blue was used for specimen 7. The trachea and right and left principal bronchi are lined with a pseudostratified ciliated columnar epithelium with occasional goblet cells. The secondary and tertiary bronchi and the primary and secondary bronchioles are lined by a simple ciliated columnar epithelium. The terminal bronchioles and a portion of the respiratory bronchioles are lined by a simple ciliated cuboidal epithelium. The terminal portion of the respiratory bronchioles and the alveolar ducts are lined with simple squamous epithelium. Alveoli are lined by type I and II pneumocytes. Tracheal glands are present in the tela submucosa. The fibromusculocartilaginous tunic of the trachea consists of c-shaped cartilage rings and the trachealis muscle. A lamina muscularis mucosa begins in the intrapulmonary portion of the principal bronchus and continues into the respiratory bronchioles. Bronchial glands are present in the propria submucosa and tela submucosa of the principal bronchi. The musculocartilaginous tunic is localized to the extrapulmonary portion of the principal bronchus. The bronchial cartilages are irregular shaped plates and limited to the extrapulmonary portion of the principal bronchus. The visceral pleura is a simple squamous mesothelium covering the outer surface of the lung.

Reproductive tract vasculature of the female emu (dromaius novaehollandiae).

The arterial supply of the ovary and oviduct is provided by the ovarian artery, cranial oviductal artery, accessory cranial oviductal artery, middle oviductal artery, caudal oviductal artery and the medial and lateral vaginal arteries. These arteries supply various regions of the oviduct and are branches of either the left cranial renal artery, left external iliac artery, left middle renal artery, left lateral caudal artery or the left pudendal artery. The veins that drain the reproductive tract are satellite vessels to each artery that supplied the tract.