Silk Production is one of the most prominent characteristics of spiders. The silk is extruded through spigots located on the spinnerets, which are single- to multimembered paired appendages at the end of the abdomen. Most extant spiders have three pairs of spinnerets, and in between either a cribellum (spinning plate) or a colulus (defunct vestigial organ), dividing these spiders into cribellate and ecribellate species. Previous research has shown that cribellate and ecribellate spiders differ not only in the composition of their spinning apparatus but also in the kinematics of spinneret movements during silk spinning. The objective of this study was to determine whether the differences in spinneret movements are solely due to variations in the degrees of freedom of the spinnerets or whether they are based on differences in muscular anatomy. This was accomplished by analyzing micro-computed tomography scans of the posterior abdomen of each three cribellate and ecribellate species. It was found that the number of muscles did not differ between cribellate and ecribellate species, but there were distinct differences between the species within each group. Muscle thickness, particularly of the posterior median spinneret, varied slightly between groups, with cribellate spiders exhibiting more robust muscles, possibly to aid in the combing process during cribellar thread production. Interestingly, the vestigial colulus still possessed muscles, that could be homologized with those of the cribellum. This initial exploration into spinneret anatomy using micro-CT data reveals that despite being small appendages, the spider spinnerets are equipped with a complex musculature that enables them to perform fine-scaled maneuvers to construct different fibre-based materials.