The Distribution of Muscles Fibers and Their Types in the Female Rat Urethra: Cytoarchitecture and Three-Dimensional Reconstruction

Authors

  • Seh Hong Lim,

    1. Department of Veterinary Medicine, College of Veterinary Medicine, National Chung-Hsing University, Taichung, Taiwan
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    • Seh Hong Lim and Tsyr-Jiuan Wang contributed equally to this work.

  • Tsyr-Jiuan Wang,

    1. Department of Nursing, National Taichung University of Science and Technology, Taichung, Taiwan
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    • Seh Hong Lim and Tsyr-Jiuan Wang contributed equally to this work.

  • Guo-Fang Tseng,

    1. Department of Anatomy, College of Medicine, Tzu-Chi University, Hualien, Taiwan
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  • Yee Fun Lee,

    1. Institute of Biomedical Science, Department of Life Sciences, National Chung-Hsing University, Taichung, Taiwan
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  • Yong-San Huang,

    1. Department of Veterinary Medicine, College of Veterinary Medicine, National Chung-Hsing University, Taichung, Taiwan
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  • Jeng-Rung Chen,

    Corresponding author
    1. Department of Veterinary Medicine, College of Veterinary Medicine, National Chung-Hsing University, Taichung, Taiwan
    • Division of Urology, Department of Surgery, Taichung Veterans General Hospital, Taichung, Taiwan
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  • Chen-Li Cheng

    Corresponding author
    • Division of Urology, Department of Surgery, Taichung Veterans General Hospital, Taichung, Taiwan
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Correspondence to: Dr. Jeng Rung Chen, Department of Veterinary Medicine, National Chung-Hsing University, No. 250, Kuo Kuang Road, Taichung 402, Taiwan. Fax: +886-422-859-398. E-mail: chenjr@dragon.nchu.edu.tw or Dr. Chen-Li Cheng, Division of Urology, Department of Surgery, Taichung Veterans General Hospital, No. 160, Sec. 3, Chung-Kang Rd., Taichung, Taiwan. Fax: +886-423-593-160. E-mail: cheng20011@gmail.com

ABSTRACT

An attempt to explore urethral cytoarchitecture including the distribution of smooth muscles and fast and slow striated muscles of adult female Sprague Dawley rat—a popular model in studying lower urinary tract function. Histological and immunohistochemical stainings were carried out to investigate the distribution of urethral muscle fibers and motor end plates. The urethral sphincter was furthermore three-dimensionally reconstructed from serial histological sections. The mucosa at the distal urethra was significantly thicker than that of other segments. A prominent inner longitudinal and outer circular layer of smooth muscles covered the proximal end of urethra. Thick circular smooth muscles of the bladder neck region (urethral portion) decreased significantly distalward and longitudinal smooth muscles became 2- to 3-fold thicker in the rest of the urethra. An additional layer of striated muscles appeared externally after neck region (urethra) and in association with motor end plates ran throughout the remaining urethra as the striated sphincter layer. Most striated muscles were fast fibers while relatively fewer slow fibers often concentrated at the periphery. A pair of extraneous striated muscles, resembling the human urethrovaginal sphincter muscles, connected both sides of mainly the distal vagina to the dorsal striated muscles in the wall of the middle urethra. The tension provided by this pair of muscles, and in conjunction with the striated sphincter of the urethral wall, was likely to function to suspend the middle urethra and facilitates its closure. Comprehensive morphological data of urethral sphincter offers solid basis for researchers conducting studies on dysfunction of bladder outlet. Anat Rec, 296:1640–1649, 2013. © 2013 Wiley Periodicals, Inc.

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