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The peritoneum has several folds on its surface that indicate the position of underlying structures. Identify the fold covering the ductus (vas) deferens, which enters the abdominal cavity via the deep inguinal ring and courses inferiorly and medially onto the posterior surface of the
urinary bladder.

Links and References:
Grant's: 3.17
Netter (1ed.): 342, 344 (2ed.): 338, 340
Rohen/Yokochi: 316