Muscle tissue which is unstriated, composed primarily of smooth muscle fibers surrounded by a reticulum of collagen and elastic fibers. Smooth muscle differs from striated muscle in the much higher actin/myosin ratio, the absence of conspicuous sarcomeres and the ability to contract to a much smaller fraction of its resting length[GO].

Glatte:Muskelzellen.jpg

Involuntary muscle tissue consisting of uninucleate spindle-shaped fibers.[AAO], A non-striated muscle that is composed of spindle-shaped cells. Smooth muscle usually is organized into sheets that line cavitated organs.[TAO]

involuntary muscle, textus muscularis nonstriatus, non-striated muscle, smooth muscle

visceral muscle, visceral muscle tissue

uberon

textus muscularis levis; textus muscularis nonstriatus

(...) the first bilateral animals possessed only smooth muscles with the molecular repertoire necessary to build a striated muscle. (...) it is more parsimonious to regard striated muscle cells as a sister cell type to the smooth muscle cells. In this scenario, striated and smooth muscles would have arisen in the stem lineage that led to the Nephrozoa (i.e. all Bilateria exclusive the acoelomorphs) (Hejnol et al., 2009), from an 'acoel-like' smooth muscle, by segregation and divergence of functions and through differential recruitment of additional genes[well established][VHOG]

UBERON:0001135

http://purl.obolibrary.org/obo/uberon.owl, http://purl.obolibrary.org/obo/cl.owl

GO uses visceral and smooth interchangeably. However visceral can also be used in the sense of the viscera. Many fly annotations to smooth muscle terms. If we want to be inclusive of insects have to have a general definition of tissue that includes cells.