part_of part of part of composed primarily of organ musculature muscle organ FMA:5022 It seems clear that the metazoan ancestor inherited from its unicellular descendants an actin cytoskeleton and motor-proteins of the myosin superfamily. Within metazoans, these two molecules were arranged into effective contractile units, the muscles. The basic trends for muscle evolution are already expressed in the diploblastic taxa.[well established][VHOG] AAO:0011066 galen:Muscle TAO:0005145 EMAPA:37474 uberon EMAPA:32715 VHOG:0001245 MA:0000015 muscle UBERON:0001630 XAO:0000172 Organ consisting of a tissue made up of various elongated cells that are specialized to contract and thus to produce movement and mechanical work[GO]. EV:0100146 ZFA:0005145 SCTID:71616004 muscular GAID:131 OpenCyc:Mx4rv2kf-5wpEbGdrcN5Y29ycA Portion of tissue composed of contractile fibers.[TAO] muscle tissue muscle structure