ction ▁of ▁the ▁walls ▁during ▁breath ing . ▁ ▁Type ▁I ▁p neum ocy tes ▁are ▁unable ▁to ▁rep licate ▁and ▁are ▁sus cept ible ▁to ▁to xic ▁ins ult s . ▁In ▁the ▁event ▁of ▁damage , ▁type ▁II ▁cells ▁can ▁pro l ifer ate ▁and ▁differenti ate ▁into ▁type ▁I ▁cells ▁to ▁compens ate . ▁ ▁Type ▁II ▁cells ▁ ▁Type ▁II ▁cells ▁are ▁the ▁most ▁numerous ▁cells ▁in ▁the ▁al ve oli , ▁yet ▁do ▁not ▁cover ▁as ▁much ▁surface ▁area ▁as ▁the ▁squ am ous ▁type ▁I ▁cells . ▁Type ▁II ▁cells ▁in ▁the ▁al ve olar ▁wall ▁contain ▁secret ory ▁gran ular ▁organ elles ▁known ▁as ▁l am ell ar ▁bodies ▁that ▁f use ▁with ▁the ▁cell ▁memb ran es ▁and ▁se crete ▁pul mon ary ▁sur fact ant . ▁This ▁sur fact ant ▁is ▁a ▁film ▁of ▁fat ty ▁subst ances , ▁a ▁group ▁of ▁ph osph ol ip ids ▁that ▁reduce ▁al ve olar ▁surface ▁t ension . ▁The ▁ph osph ol ip ids ▁are ▁stored ▁in ▁the ▁l am ell ar ▁bodies . ▁Without ▁this ▁co ating , ▁the ▁al ve oli ▁would ▁collapse . ▁The ▁sur fact ant ▁is ▁continu ously ▁released ▁by ▁ex oc yt osis . ▁Re infl ation ▁of ▁the ▁al ve oli ▁following ▁ex hal ation ▁is ▁made ▁easier ▁by ▁the ▁sur fact ant , ▁which ▁reduces ▁surface ▁t ension ▁in ▁the ▁thin ▁fluid ▁co ating ▁of ▁the ▁al ve oli . ▁The ▁fluid ▁co ating ▁is ▁produced ▁by ▁the