▁References ▁ ▁Emp oris : ▁M TA ▁Building ▁Mc Lar and ▁Vas quez ▁E ms iek ▁& ▁Part ners : ▁M TA ▁Head q iar ters ▁ ▁Category : Sk ys cra per ▁office ▁buildings ▁in ▁Los ▁Angeles ▁Category : Build ings ▁and ▁structures ▁in ▁Dow nt own ▁Los ▁Angeles ▁Category : G overn ment ▁buildings ▁in ▁Los ▁Angeles ▁Category : Office ▁buildings ▁completed ▁in ▁ 1 9 9 5 ▁Category : 1 9 9 5 ▁establish ments ▁in ▁California ▁Category : 1 9 9 0 s ▁architecture ▁in ▁the ▁United ▁States <0x0A> </s> ▁A ▁pul mon ary ▁al ve ol us ▁( pl ural : ▁al ve oli , ▁from ▁Latin ▁al ve ol us , ▁" l ittle ▁cav ity ") ▁is ▁a ▁h ollow ▁cup - sh aped ▁cav ity ▁found ▁in ▁the ▁lung ▁par en chy ma ▁where ▁gas ▁exchange ▁takes ▁place . ▁L ung ▁al ve oli ▁are ▁found ▁in ▁the ▁ac ini ▁at ▁the ▁beginning ▁of ▁the ▁resp ir atory ▁zone . ▁They ▁are ▁located ▁sp ars ely ▁on ▁the ▁resp ir atory ▁bron chi oles , ▁line ▁the ▁walls ▁of ▁the ▁al ve olar ▁du ct s , ▁and ▁are ▁more ▁numerous ▁in ▁the ▁blind - ended ▁al ve olar ▁sac s . ▁The ▁ac ini ▁are ▁the ▁basic ▁units ▁of ▁resp iration , ▁with ▁gas ▁exchange ▁taking ▁place ▁in ▁all ▁the ▁al ve oli ▁present . ▁The ▁al ve olar ▁memb rane ▁is ▁the ▁gas ▁exchange ▁surface , ▁surrounded ▁by ▁a ▁network ▁of ▁cap ill