part_of starts_at ends_at genitourinary system mesenchyme cloaca cloaca associated mesenchyme EMAPA:27642 EMAPA:27581 anatomical_structure The cloaca associated mesenchyme (clam) (TS:17-TS:20) is the mesenchyme surrounding the cloacal epithelium of the cloaca, an epithelial lined cavity derived from endoderm, seen early in embryonic development located at the posterior end of the embryo. urinary system mesenchyme TS17 TS20