Growth of the Organ Over Gestation Time:

How does a single cell grow into a whole lung?

1. Tissues are in a state of tension where all their cells “hang” on each other.
2. They pull on a flexible matrix of fibrous proteins and sugars that surround and support every cell.
3. Cells beneath the growing lungs release proteins that unravel and make small regions in the tensed matrix thinner.
4. These spots stretch more than the rest of the matrix, causing a thinning.
5. These areas are stretched more than neighboring parts of lung tissue.
6. If cells feel that extra tension, they begin to grow.
7. Cells will bud and branch outwardly, forming new sacs. But if the cells feel a decrease in tension, they stop the growth.
8. Growing lungs need supplies of blood to function.

Dr.  Donald Ingber, a Judah Folkman Professor of Vascular Biology at the Medical School in Harvard University, has seen an extension of small, nearby blood vessels, also known as capillaries, growing in series with new air sacs. He and his team conducted an experiment to test whether or not adjusting the tension in developing mouse lungs would allow the lung tissue to bud outward; and, it did. For more information on his discoveries, click on the link below.

http://www.news.harvard.edu/gazette/2005/03.24/03-lung.html