▁the ▁f au ces . ▁Its ▁roof ▁is ▁formed ▁by ▁hard ▁pal ate ▁at ▁the ▁front , ▁and ▁a ▁soft ▁pal ate ▁at ▁the ▁back . ▁The ▁u v ula ▁projects ▁down wards ▁from ▁the ▁middle ▁of ▁the ▁soft ▁pal ate ▁at ▁its ▁back . ▁The ▁floor ▁is ▁formed ▁by ▁the ▁my lo hy oid ▁mus cles ▁and ▁is ▁occupied ▁mainly ▁by ▁the ▁tongue . ▁A ▁m uc ous ▁memb rane ▁– ▁the ▁or al ▁m uc osa , ▁lines ▁the ▁sides ▁and ▁under ▁surface ▁of ▁the ▁tongue ▁to ▁the ▁g ums , ▁l ining ▁the ▁inner ▁aspect ▁of ▁the ▁j aw ▁( m and ible ). ▁It ▁receives ▁the ▁secret ions ▁from ▁the ▁subm and ib ular ▁and ▁sub ling ual ▁sal iv ary ▁g lands . ▁ ▁Or ifice ▁▁ ▁While ▁shut , ▁the ▁or ifice ▁of ▁the ▁mouth ▁forms ▁a ▁line ▁between ▁the ▁upper ▁and ▁lower ▁lip . ▁In ▁fa cial ▁expression , ▁this ▁mouth ▁line ▁is ▁icon ically ▁sh aped ▁like ▁an ▁up - open ▁par ab ola ▁in ▁a ▁smile , ▁and ▁like ▁a ▁down - open ▁par ab ola ▁in ▁a ▁f rown . ▁A ▁down - turn ed ▁mouth ▁means ▁a ▁mouth ▁line ▁forming ▁a ▁down - turn ed ▁par ab ola , ▁and ▁when ▁permanent ▁can ▁be ▁normal . ▁Also , ▁a ▁down - turn ed ▁mouth ▁can ▁be ▁part ▁of ▁the ▁presentation ▁of ▁Pr ader - W illi ▁synd rome . ▁ ▁N erve ▁supply ▁The ▁teeth ▁and ▁the ▁period ont ium ▁( i