You wanted to know
Fifth-graders in Katherine Crawford's class at West Oak Middle School in Mundelein asked, "How do people grow?"
Suggested readingSuggested reading
The Fremont Public Library District in Mundelein suggests these titles about DNA, cells and nutrition:
Ÿ "Amazing DNA" by Rebecca Johnson
Ÿ "The World Of The Cell: Life On A Small Scale" by Robert Snedden
Ÿ "Human Body Q&A" by Richard Walker
Ÿ "Eat Right! How You Can Make Good Food Choices" by Matt Doeden
Two factors drive the growth process in people -- information within a cell and nutrition. It's the same for all things in nature, cells make things grow and nutrition creates the best chance for a healthy life cycle.
Paul Karnstedt, biology teacher at Warren Township High School in Gurnee, said, "Almost everything is made up of smaller objects. If you have ever built anything out of Legos, you make a large object using a bunch of smaller blocks. All living things are made from building blocks of their own called cells."
Proteins, molecules and genetic information regulate cell size, making them neither too big nor too small.
"Cells are extremely small -- there are trillions of them in a human body," Karnstedt said. "Cells divide into new cells, which allow them to make copies of themselves."
The whole process is set into motion immediately when an egg is fertilized. Cells double exponentially, which means that each time new cells are created and grow to the correct size, a new set of cells is formed that is double the number of the previous set. Two cells activate four cells, four cells trigger eight, and so on. Each of these cells contains the DNA code that will dictate height, eye and hair color. Chemicals within cells get to work on manufacturing other cells like heart cells, skin cells and bones cells.
"When you grow, it is because your cells are dividing and making new cells over and over again," Karnstedt said.
"When this happens, there are more cells that are making up your body. This means that there are more building blocks and your body gets bigger. The cells in your bones, in particular, divide at a very fast rate when you are young. This creates more cells in your bones and makes your bones bigger, which makes you taller."
Nutrition also helps to make you taller and stronger. Have you ever noticed that sometimes grandmas and grandpas from "the old country" are much smaller than their children and grandchildren?
Balanced nutrition, including a diet with protein and calcium, gives cells the best chance to reach their best potential. Exercise also helps bodies to be strong and support healthy growth.
Do cells ever stop growing? "When areas of your body stop growing, it is because the cells have stopped dividing," Karnstedt explained.
Cells are continually replaced, but the growing phase has a limit. Most people have stopped growing by age 25.