Cov pos hniav yog cov cuab yeej kho mob ua los ntawm cov khoom siv organic siab molecular polymer, uas yog yooj yim rau kev kho hniav thiab ntxiv.
Cov xim zoo ib yam li mucosa, thiab nws zoo nkauj dua. Cov khoom siv ntau lawm yog qhov yooj yim, kev ua haujlwm yooj yim, thiab kev lag luam yooj yim rau kev kho hniav thiab ntxiv rau. Nws yog feem ntau siv ib qho hauv tsev kho mob. Txawm li cas los xij, nws lub zog yog qhov tsawg, thiab nws yuav tsum muaj qee qhov tuab. Cov khoom siv yog cov organic siab molecular polymer, uas yooj yim rau lub hnub nyoog, yog tus neeg xyuas pib tsis zoo, muaj qhov kub tsis zoo, thiab tsis yooj yim rau kev tu nws tus kheej.
