The Musculature of the Mouse Tail is Characterized by Metameric Arrangements of Bicipital Muscles

Abstract

This is the first report, to our knowledge, of the full characterization of the musculature of the mouse tail. Bicipital muscles form a major part of the tail musculature. The tail tendons originate with fusiform muscle from the dorsal and ventral lumbo-sacro-coxal regions and are inserted into the coccygeal vertebrae (extrinsic muscles of the tail). Each coccygeal vertebra has short muscles that terminate on the adjacent vertebrae (intrinsic muscles of the tail). The short muscle and its corresponding tail tendon are joined, thereby forming a bicipital muscle that is inserted into the coccygeal process. A geographical correspondence is strictly maintained between the origin of the tendon in the lumbo-sacro-coxal region and the insertion of the bicipital muscle in the coccygeal vertebrae. In other words, the organization of the tail musculature is based upon repetitions of fusion between the extrinsic and intrinsic muscles at each coccygeal vertebral level. This design is referred to as the metameric arrangement of the bicipital muscles. The organization, arrangement and function of muscles in the tail have features in common with those muscles in the digits of the human extremities.