. ▁Can cer ▁in ▁a ▁ser ous ▁cav ity ▁is ▁called ▁a ▁ser ous ▁car cin oma . ▁Cy top ath ology ▁evaluation ▁is ▁recommended ▁to ▁evaluate ▁the ▁causes ▁of ▁eff us ions ▁in ▁these ▁cav ities . ▁ ▁Ex amples ▁Sal iva ▁consists ▁of ▁m uc us ▁and ▁ser ous ▁fluid ; ▁the ▁ser ous ▁fluid ▁contains ▁the ▁en zym e ▁am yl ase , ▁which ▁is ▁important ▁for ▁the ▁dig estion ▁of ▁car bo h yd r ates . ▁Minor ▁sal iv ary ▁g lands ▁of ▁von ▁Eb ner ▁present ▁on ▁the ▁tongue ▁se crete ▁the ▁lip ase . ▁The ▁par ot id ▁g land ▁produces ▁purely ▁ser ous ▁sal iva . ▁The ▁other ▁major ▁sal iv ary ▁g lands ▁produce ▁mixed ▁( ser ous ▁and ▁m uc us ) ▁sal iva . ▁ ▁Another ▁type ▁of ▁ser ous ▁fluid ▁is ▁secret ed ▁by ▁the ▁ser ous ▁memb ran es ▁( ser osa ), ▁two - layer ed ▁memb ran es ▁which ▁line ▁the ▁body ▁cav ities . ▁Ser ous ▁memb rane ▁fluid ▁collect s ▁on ▁micro v illi ▁on ▁the ▁outer ▁layer ▁and ▁acts ▁as ▁a ▁lub ric ant ▁and ▁reduces ▁fr iction ▁from ▁mus cle ▁movement . ▁This ▁can ▁be ▁seen ▁in ▁the ▁l ungs , ▁with ▁the ▁ple ural ▁cav ity . ▁ ▁Blood ▁ser um ▁is ▁the ▁component ▁of ▁blood ▁that ▁is ▁neither ▁a ▁blood ▁cell , ▁nor ▁a ▁cl ot ting ▁factor . ▁Blood ▁ser um ▁and ▁blood ▁pl asma ▁are ▁similar , ▁but ▁ser um