Augsburger H R, Cruz-Orive L M
Institute of Veterinary Anatomy, University of Zürich, Switzerland.
Histochemistry. 1994 Nov;102(5):373-82. doi: 10.1007/BF00268908.
The M. urethralis was morphologically investigated in ten medium-sized female dogs of different breeds and age, as well as histochemically and stereologically analysed in a homogeneous group of five female beagles. Macroscopically, the muscle was essentially confined to the distal third and most strongly developed in the fourth quarter of the urethra. Here, it surrounded the urethra transversely at the ventral and lateral aspects, passing with its caudal fibres dorsally onto the vagina. The muscle fibres were assembled in groups of different sizes and usually separated by thick connective tissue septae. Based on the myofibrillar actomyosin ATPase (mATPase) reaction, type I and two main subtype II fibres could be differentiated. Type II fibres were, however, indistinguishable by their metabolic enzyme activities since both subclasses displayed oxidative-glycolytic properties. The subtype II fibres containing the more acid-labile mATPase activity were classified as IIA, whereas the other main subtype was designated IIS (subtype) and considered as peculiar to the dog. In addition, the investigation revealed a rare fibre type exhibiting the histochemical profile of IIC fibres. There was no evidence of classical glycolytic IIB fibres. The M. urethralis was composed of 24% type I and 76% type II fibres with an average diameter of 34.9 and 28.5 microns, respectively. Connective tissue constituted 52.8% of the total muscle volume. Due to the predominance of fast twitch II fibres, the urethral muscle is not designed to maintain a high tone over long periods of time. Its primary role is to function rapidly and intermittently guaranteeing urinary continence during stress situations when other continence factors are overburdened.
对10只不同品种和年龄的中型雌性犬的尿道肌进行了形态学研究，并对5只雌性比格犬的同质组进行了组织化学和体视学分析。宏观上，该肌肉主要局限于尿道的远端三分之一，在尿道的第四象限发育最强。在这里，它在尿道的腹侧和外侧横向环绕尿道，其尾侧纤维背侧延伸至阴道。肌纤维聚集成不同大小的组，通常被厚厚的结缔组织间隔分开。基于肌原纤维肌动球蛋白ATP酶（mATPase）反应，可以区分出I型和两种主要的II型亚型纤维。然而，II型纤维通过其代谢酶活性无法区分，因为两个亚类都表现出氧化-糖酵解特性。含有更酸不稳定mATPase活性的II型亚型纤维被归类为IIA，而另一个主要亚型被指定为IIS（亚型），被认为是犬特有的。此外，研究还发现了一种罕见的纤维类型，其组织化学特征与IIC纤维一致。没有经典糖酵解IIB纤维的证据。尿道肌由24%的I型纤维和76%的II型纤维组成，平均直径分别为34.9和28.5微米。结缔组织占肌肉总体积的52.8%。由于快速收缩的II型纤维占优势，尿道肌不适合长时间保持高张力。它的主要作用是在其他控尿因素负担过重的应激情况下快速间歇性发挥作用，保证控尿。
