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Bones in the heart skeleton of the otter (Lutra lutra).
Egerbacher M,
Weber H,
Hauer S
Abstract
In most mammalian species the cardiac
skeleton is composed of coarse collagen fibres, fibrocartilage, and pieces of
hyaline cartilage. Bone, the os cordis, is a regular constituent of the ruminant
heart. The cardiac skeleton of the otter (Lutra lutra) has not previously been
described. The skeleton in 30 otter hearts was studied by x-ray analysis and
light microscopy. Serial sections were cut parallel to the atrioventricular
plane and histochemical staining methods were performed to identify connective
tissue fibres, glycosaminoglycans, mineral deposits, and bone. Age and sex of
the animals under investigation were considered. The otter heart skeleton was
composed of coarse collagen fibres with intercalated pieces of fibrous and/or
hyaline cartilage, calcified cartilage, and lamellar bone with red or white
marrow. Pieces of hyaline cartilage were not clearly defined: a perichondrial
layer was missing and coarse connective tissue continuously transformed into
fibrous and hyaline cartilage. In both sexes the amount of cartilage and bone
were found to increase with age. Our results establish the presence of bony
material in the heart skeleton of the otter, a small mammalian species. This
finding indicates that differentiation of bone is not exclusively related to the
size of the organ. Increasing amounts of calcified cartilage and bone correlated
with increasing age.
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