Nrog rau kev txhim kho txuas ntxiv ntawm tib neeg txoj kev nyob thiab kev noj ntau ntau, txhua yam ntawm lub hnab tau dhau los ua cov khoom siv tseem ceeb rau tib neeg. Cov khoom tawv tawv yog cov thawv, hnab, hnab looj tes, cov neeg tuav daim pib, siv tawv, thiab lwm yam khoom tawv uas ua los ntawm tawv thiab cov ntaub ntawv tsis yog tawv. Kev lag luam tawv khoom lag luam suav nrog lub nra, hnab tes thiab cov khoom siv tawv me uas ua los ntawm cov khoom tawv tawv thiab cov khoom siv hloov pauv.