Njerwa ndi bwino - zomangira zomangamanga, ndipo zimagwiritsidwa ntchito kwambiri m'minda yambiri. Monga limodzi la mafupa omanga, kufunikira kwa njerwa kumakulitsa pang'onopang'ono. Inde, njirayi ndiyosagwirizana ndi kugwiritsa ntchito makina opanga njerwa. Ndi ver
Makina opanga okhawo opanga okha ndi zida zofunikira komanso zofunikira mu malonda amakono. Pofuna kuonetsetsa kuti zida za zidazi, zikusintha bwino zopanga ndikuwonetsetsa kuti ali ndi chitetezo, tili ndi mawonekedwe