engleski

Muscle variations – from embryonic development to clinical importance

Introduction Muscle variations are defined as the appearance of additional muscle bundle or belly, unusual muscle origin or termination, as well as complete absence of a muscle. Muscle variations are very interesting regarding their embryonic development, but their importance increases during some surgical procedures. In our previous studies we described morphology and appearance of muscle variations in a dog, but for complete understanding of muscle variations it is necessary to investigate their embryonic development on the level of single cell. Methods All animals were conserved with 4% formalin fixative solution and dissected within a gross anatomy course at the Faculty of Veterinary Medicine University of Zagreb. The animals were handled in accordance with the Croatian Animal Protection Act (2006), and the study protocol was approved by the Ethics Committee of the Faculty of Veterinary Medicine. Results In our investigations muscle variations were observed in 22.8% cases. Although, muscle variations were observed in specific body regions, mostly in pectoral girdle muscles (brachiocephalicus, omotransversarius, rhomboideus capitis and serratus ventralis cervicis), neck muscles (strenocephalicus, sternohyoideus, stylohyoideus and scalenus dorsalis) and hindlimb muscles (sartorius), all observed variations were connected with the limbs. Described muscle variations were present as thin additional muscle bundle. Additional muscle bundles were innervated like a muscles from which they originate and the same innervation suggests the same embryonic origin. Conclusion Most of described muscle variations were connected with the limbs. According to this, we consider that during limb development, which commences during the fourth week in dogs, some myotomal cells fuse with the neighbour muscles during limbs outgrowth. Moreover, in limb development very important events were series rotations which participated in specification of the limb axes. According to this facts we conclude that limb rotation contribute in development of muscle variations. Although, muscle variation have embryonic importance, their most importance was topographic position during some surgical procedures.

muscle variation; dog; embryonic development; clinical importance

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