transversus abdominis /-vur″səs/ , one of a pair of transverse abdominal muscles that are the anterolateral muscles of the abdomen, lying immediately under the internal abdominal oblique. Arising from the inguinal ligament, the iliac crest, the thoracolumbar fascia, and the last six ribs, it inserts into the linea alba. It serves to constrict the abdomen and, by compressing the contents, to assist in urination, defecation, emesis, parturition, and forced expiration. Also called transversalis. Compare pyramidalis, rectus abdominis.
