Gross morphology of the African lion ( Panthera leo ) heart

Numeric and morphological studies of the African lion (Panthera leo leo) pectoral limb

Background

The Importance of the appendicular skeleton in the conformation, shape and physiology of wild animals especially carnivores for adaptation and survival cannot be overemphasized, as limited and obsolete information on the bones of the forelimb necessitated this study. Matured adult African lions (Male and female) that weighed 173 kg and 112 kg were obtained at different times after post mortem examinations of their carcasses. Bone preparation was achieved via cold water maceration after proper skin and muscle removal to a barest minimum.

Results

The acromion process of the scapula consisted of a ventral hamate and caudal suprahamate processes. The Clavicle was absent in this species. The musculospiral groove of the humerus was more or less absent while its supracondyloid foramen and crest were positioned above the medial condyle and lateral condyle respectively. The radio-ulna presented a twisted appearance with the radius slightly curved thereby creating an extensive interosseous space that spanned its entire length. The seven (7) carpal bones were uniquely arranged in two rows while the 5 metacarpals anchored 5 digits with 3 phalanges except the first with 2 phalanges each. Two sesamoid bones were located on the ventral surface of each Metacarpophalangeal joint. None was seen on its dorsal surface. The 3rd phalanx had a unique appearance with a crescent plate projecting from the ventral cavity. The average total number of bones constituting the pectoral limb was 80.

Conclusion

Numerical information and detailed anatomical features of the pectoral limb bones of the African lion (Panthera leo leo) have added some valuable literature to science. This further serves as a baseline data for future scientific exposition on this species.

Anatomy of the heart with the highest heart rate

Shrews occupy the lower extreme of the seven orders of magnitude mammals range in size. Their hearts are large relative to body weight and heart rate can exceed a thousand beats a minute. It is not known whether traits typical of mammal hearts scale to these extremes. We assessed the heart of three species of shrew (genus Sorex) following the sequential segmental analysis developed for human hearts. Using micro‐computed tomography, we describe the overall structure and find, in agreement with previous studies, a large and elongate ventricle. The atrial and ventricular septums and the atrioventricular (AV) and arterial valves are typically mammalian. The ventricular walls comprise mostly compact myocardium and especially the right ventricle has few trabeculations on the luminal side. A developmental process of compaction is thought to reduce trabeculations in mammals, but in embryonic shrews the volume of trabeculations increase for every gestational stage, only slower than the compact volume. By expression of Hcn4, we identify a sinus node and an AV conduction axis which is continuous with the ventricular septal crest. Outstanding traits include pulmonary venous sleeve myocardium that reaches farther into the lungs than in any other mammals. Typical proportions of coronary arteries‐to‐aorta do not scale and the shrew coronary arteries are proportionally enormous, presumably to avoid the high resistance to blood flow of narrow vessels. In conclusion, most cardiac traits do scale to the miniscule shrews. The shrew heart, nevertheless, stands out by its relative size, elongation, proportionally large coronary vessels, and extent of pulmonary venous myocardium.