Chacon-Arellano J T, Woolley D M
J Anat. 1980 Sep;131(Pt 2):263-73.
Smooth muscle cells are present in the tunica albuginea testis of the horse, pig and sheep. typical fusiform muscle cells constitute a distinct layer up to 0.3 micrometer thick in the horse; there are fewer muscle cells, mainly of the branched form, in the pig; whereas in the sheep the muscle component is least well developed, with some cells intermediate in form between smooth muscle cells and fibroblasts (myofibroblasts). Attention is drawn to the continuity of this capsular muscle with the smooth muscle associated with the vasculature of the spermatic cord in the horse. This association suggests that the capsular muscle is unlikely to have a primary role in sperm transport from the testis.
马、猪和羊的睾丸白膜中存在平滑肌细胞。典型的梭形肌细胞在马的睾丸白膜中构成一个独特的层，厚度可达0.3微米；猪的肌细胞较少，主要为分支状；而在羊中，肌肉成分发育最不完善，一些细胞的形态介于平滑肌细胞和成纤维细胞（肌成纤维细胞）之间。值得注意的是，马的这种包膜肌与精索血管相关的平滑肌是连续的。这种关联表明，包膜肌在精子从睾丸的运输中不太可能起主要作用。
