part_of starts_at ends_at genitourinary system mesenchyme urogenital sinus mesenchyme of urogenital sinus The mesenchyme of urogenital sinus (mugs) is the mesenchyme surrounding the urogenital sinus epithelium. Marked by Gli1, Ptch1, Bmp4, Raldh2. Derived from mesoderm. Subdivided into mesenchymal layer of primitive bladder (rostral/anterior), mesenchyme of primitive bladder-caudal urogenital sinus transition zone and caudal urogenital sinus mesenchyme (caudal/posterior). EMAPA:31500 anatomical_structure EMAPA:31519 urinary system mesenchyme TS18 TS26