Q&A - BIOLOGY by Miller & Levine

QUESTION: We are using your Biology book in our 10th grade classroom. We have a question that we can not find an answer. On page 248 Analyzing Data – Life Spans of Human Cells, it indicates that heart and skeletal muscle cells do not reproduce. Does that mean that you are born with all the cells you will have? Or is there a way to make new cells? What happens after surgery when you cut the muscle tissue? (from Karen, a teacher in Oregon).

ANSWER: Thanks very much for your note! In general the information in that chart is correct. Skeletal muscle cells form by the fusion of smaller cells called myoblasts during embryonic development. When a muscle grows in size, the existing cells simply add new muscle fibers. The same is true as the heart increases in size during development into adulthood.

And, when the heart is injured (due to a heart attack, for example), unfortunately the remaining muscle cells cannot grow back to replace the injured ones. The same is true with skeletal muscle.

However (and here's where things get interesting) this does not mean that the muscle itself cannot grow back. Skeletal muscle contains another kind of cell called a "satellite cell," or "myogenic satellite cell." These seem to be stem cells for skeletal muscle, and they are able to develop into new myoblasts following muscle injury, and form new cells to help repair the damage. Whether the heart muscle contains similar cells is of very great interest, of course, and is still controversial.

You might take a look at the research done in Ron Allen's lab at the University of Arizona for some further information on these cells:

http://animal.cals.arizona.edu/faculty/facdisp.php?email=rallen@ag.arizona.edu

There's a great deal of interest in these cells in the pharmaceutical industry, of course. Here's another reference to them:

http://www.mitils.co.jp/research/department/unit/hashimoto/hashimoto_e.html

Hope this helps to answer your question!

Questions and Answers about BIOLOGY by Ken Miller and Joe Levine

Questions and Answers about BIOLOGY

by Ken Miller and Joe Levine