1.4.2  Using nutrients to build the body

For growth: A child starts to grow as a single cell inside its mother. The cell absorbs nutrients; it grows and divides into two cells. The cell uses nutrients as building materials for the new cell and other nutrients for energy to do the work of building. Each cell then absorbs more nutrients to grow larger and divide again. The cells continue to absorb nutrients and to grow and divide until there are millions of cells which form different tissues such as skin, muscle and bone. The child’s body also makes fluids such as blood, which nourishes and protects the cells.

For pregnancy: During pregnancy, a woman needs body building nutrients to:

• provide the baby and placenta with nutrients to grow
• increase the size of her uterus and breasts
• make more blood and stores of fat that can be mobilised during lactation, and other nutrients.

To secrete fluids: The body has to keep making fluids such as saliva, digestive juices, tears and breastmilk because they are continually used up.

To replace cells: Most cells live only a short time. The body must build new cells to replace those that die. The need to replace cells continues throughout life. Skin is a good example. The outside layer of the skin is already dead. All the time new cells are growing under the dead cells to replace them. When you wash and dry yourself, you remove the dead cells.

If you wear shoes for a long time you get holes in the soles. But if you walk without shoes, you do not get holes in your feet, because new skin cells grow under the old cells to replace them.

To repair tissues: After injury or illness, the body makes new cells to repair the damaged tissues.