Abuur nooc ka mid ah weedhan oo aad u adag Waa'' casaan, siman oo dhalaalaya''.
Dabcan, nooc ka sii adag ee jumlada waa "Waa 'cas, jilicsan oo dhalaalaya', epithelium-keeda ayaa ka khafiifsan tan ciridka, waa non-keratinized, oo kuma xirna unugyada hoose ee xargaha".