Part V: Membranes A. Membranes are thin aheets of tiasoe that coree an mepan or liae a bedy conity. Serous memberanes line body cavities whikh do not open directh ta the eutwidc of ihe body and cover organs cantained withis the avities The term parictal is used to deseribe the serous nembeane that lines the enviy wall. The tera viserral ie wed. to describe the serous memhirane that coven the surfoc of argani wathin the cavity itself Serous membeanes produce a thin, watery secrfion, called seruas fuuld, that acts as a lutricast to redace frictson betirem organe and the willi of body arities. wileal for each dugnam. Vanctal pleirs Mranakewnty Viecrilgteras.