Morphological Description of Levator Ani Muscle in Rats

The aim of the research: the study of structural morphologic features of levator ani muscle in white laboratory rats.

Materials and methods. Five male and five female laboratory rats 300–420 g of weight were observed as an object of investigation. The experimental animals were kept in standard conditions in vivarium with the free access to water and food. The methods of preparation, histochemistry, optical and electronic microscopy were used during the investigation.

Results. It was stated that in male rats, levator ani muscle is represented by a single complex without a clear differentiation into compartments. In females, the iliocaudal and pubocaudal portions of levator ani muscle are clearly differentiated. The iliocaudal muscle is initially attached to the internal part of iliac bone, pubocaudal muscle is initially attached to the posterior part of pubic bone below pubic symphysis. The other ends of the muscles are attached through their tendons to the anterior surface of caudal vertebrae bodies Ca_III–Ca_VI. Meanwhile, iliocaudal muscle is attached more proximally to Ca_III–Ca_VI, and pubocaudal muscle is attached more distally to Ca_V–Ca_VI. The transverse sections of levator ani muscle in males and its pubocaudal portion in females are represented by polygonal muscle fibers, and the iliocaudal portion of levator ani muscle in females is represented by orbicular muscle fibers. Ultrastructural manifestations of sexual dimorphism among muscle fibers are not observed, they have got typical structure representative for transversal striated skeletal muscular tissue. On histochemical investigation the presence of I and II type of muscle fibers was determined, but glycolytic fibers (of the II type) prevailed.

Conclusion. The obtained data indicate the presence of sexual dimorphism in levator ani muscle structure in white laboratory rats. This muscle is supposed to contribute more to provide tail movements than to strengthen small pelvis wall and protect organs.

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