vitals

belly core deep depths entrails guts hold innards interior intestines penetralia recesses viscera

exterior exteriority outside

insides

bowels guts innards viscera

internal parts

bowels guts innards insides viscera

digestive organs

essential fundamental obligation precondition prerequisite requirement urgency

call cause claim compulsion demand desideratum duress essence exaction exigency godsend imperative indispensability inevitability inexorableness must must-have necessary pinch privation requisite stress want

life or death needfulness no alternative no choice sine qua non undeniability vital part

auxiliary extra trivia

desire