Descrição morfológica do coração e dos vasos da base do jacaré-do-pantanal (Caiman yacare Daudin, 1802) proveniente de zoocriadouro

External macroscopic anatomy of the Bradypus variegatus heart

ABSTRACT The sloth is known for its slow movements and arboreal habits. Most parts of its anatomy need yet to be unveiled, in order to understand the peculiarities that justify its behavior. In this sense, an investigation of the external characteristics of the heart of the three-toed sloth, Bradypus variegatus, was carried out to indicate the shape, the faces, the dimensions, the topography, and the coating of this organ. For this purpose, fifteen corpses destined for dissection and four healthy specimens were used to carry out thorax digital x-ray. Based on the obtained results, it was noticed that the heart of the species in question presents conical shape, situated obliquely in the mediastinum, is displaced to the left and has latero-lateral slight flattening. Among the animals, discrepancies were found in the organ skeletopy, which presents the tapered apex and the base, in which the large vessels can be observed, whose arrangements also proved to be variables. The heart presents faces (right and left), margins (cranial and caudal) and is surrounded by the pericardium, which gives off two ligaments, sternopericardial and phrenico pericardial. Its size is proportional to the age and length of the individual, with measurements, in general, slightly larger in males.

Arterial wall thickening normalizes arterial wall tension with growth in American alligators, Alligator mississippiensis

Arterial wall tension increases with luminal radius and arterial pressure. Hence, as body mass (M_b) increases, associated increases in radius induces larger tension. Thus, it could be predicted that high tension would increase the potential for rupture of the arterial wall. Studies on mammals have focused on systemic arteries and have shown that arterial wall thickness increases with M_b and normalizes tension. Reptiles are good models to study scaling because some species exhibit large body size range associated with growth, thus, allowing for ontogenetic comparisons. We used post hatch American alligators, Alligator mississippiensis, ranging from 0.12 to 6.80 kg (~ 60-fold) to investigate how both the right aortic arch (RAo) and the left pulmonary artery (LPA) change with M_b. We tested two possibilities: (i) wall thickness increases with M_b and normalizes wall tension, such that stress (stress = tension/thickness) remains unchanged; (ii) collagen content scales with M_b and increases arterial strength. We measured heart rate and systolic and mean pressures from both systemic and pulmonary circulations in anesthetized animals. Once stabilized alligators were injected with adrenaline to induce a physiologically relevant increase in pressure. Heart rate decreased and systemic pressures increased with M_b; pulmonary pressures remained unchanged. Both the RAo and LPA were fixed under physiological hydrostatic pressures and displayed larger radius, wall tension and thickness as M_b increased, thus, stress was independent from M_b; relative collagen content was unchanged. We conclude that increased wall thickness normalizes tension and reduces the chances of arterial walls rupturing in large alligators.

Notes on the gross anatomy of the heart of the broad-snouted caiman, Caiman latirostris (Daudin, 1802)

The broad-snouted caiman, Caiman latirostris (Daudin, 1802), is one of the six crocodilian species from Brazil. The topography, morphology and morphometry of the broad-snouted caiman heart were studied. Data were obtained from the necropsy of four adult animals, three females and one male. The hearts were removed from the coelomic cavity and fixed in 10% formalin for 48 hr for morphological and morphometric description. The heart is in the cranial mediastinum. It is caudally involved by the liver cranial margins, and ventrally by the ribs, intercostal muscles, and sternum and dorsally by the lungs. The four-chambered morphology is typical with two (right and left) atria and ventricles. Right and left aortic, pulmonary and subclavian arteries branch from the truncus arteriosus. Gubernaculum cordis is present as ligamentous folds uniting the heart apex to the pericardium. Main morphometric means are the apex-to-base length (49.86 mm), circumference (105.25 mm) and heart weight (45.03 g). The right atrium is craniocaudally longer with thicker walls, whereas the left ventricle is narrower. The topography, morphology and morphometry of the heart of C. latirostris are consistent with the anatomy of other crocodilian species.

Morphoquantitative evaluation of the heart of cutia (Dasyprocta agouti) and capybara (Hydrochoerus hydrochaeris)

ABSTRACT The cutia (Dasyprocta agouti) and capybara (Hydrochoerus hydrochaeris ) are hystricomorphic rodents of the Brazilian fauna. The wild animal anatomy is essential to the clinic and surgery practices and conservation programs. This work aimed to evaluate the heart quantitative morphology of the cutia and the capybara. For this, three hearts of cutia and three of capybaras were used from the collection of the Anatomy Sector of Domestic and Wild Animals of the Faculty of Veterinary Medicine and Animal Science of the University of São Paulo. The hearts were weighted and measured with a pachymeter. The left ventricle volume was estimated through the Cavalieri method. The hearts’ mean weight was 16.76g (cutias) and 104.2g (capybaras). The mean values for the axis, width and base dimensions were of the cutia 4.3cm, 3.3cm and 3.3cm and for the capybara were 7.6cm, 6.0cm and 6.1cm, respectively. The mean volume of the left ventricle of the cutia and the capybara was 5.03cm3 and 54.55cm3, respectively. The quantitative results of the hearts were compatible with the average body weight of the rodents. Thus, these numerical data can be applied to veterinary cardiology.