1.Introduce the general idea: human body need all kinds of nourishment during the life(such as water, inorganic acid, protein, glycolipin, microbian mineral, oxygen),blood cycle for digestion.
1.人体在命运动中需要各种营养(
、
盐、蛋白质、
类脂肪、维
质,氧气),其消化吸收需通过血液循环系统。