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.

人体在生命运动中种营养（水、无机盐、蛋白质、类脂肪、维生物矿物质，氧），化吸收通过血液循环系统。