Human cells that keep dividing
To study cell division for medical and other purposes, biologists
need human cells that continue to divide in culture in the
laboratory. In 1951, researchers at Johns Hopkins University
tried to culture a line of cells that would continue to live and
multiply. Every cell sample they tried died out in a few weeks,
because normal mammalian cells will divide only 20-50 times
in culture before they die.
Finally, cells from one sample kept dividing week after week,
and eventually, year after year. These were called HeLa cells
after their original source, a young Baltimore woman named
Henrietta Lacks. The sample had been taken from a malignant
tumor in her body. Unfortunately, she died a few months later,
but HeLa cells have been grown since that time in laboratories
around the world.
Sea Urchin Embryo Cell Division
Zebrafish development from 1 cell to hatching – 48 hours
Life Spans of Human Cells
Cell Type
Life Span
Cell Division
Lining of esophagus
2-3 days
Can divide
Lining of small intestine
1-2 days
Can divide
Lining of large intestine
6 days
Can divide
Red blood cells
Less than 120 days
Cannot divide
White blood cells
10 hours to decades
Many do not divide
Smooth muscle
Long-lived
Can divide
Cardiac (heart) muscle
Long-lived
Cannot divide
Skeletal muscle
Long-lived
Cannot divide
Neuron (nerve cell)
Long-lived
Most do not divide
1. White blood cells help protect the body from infection and diseaseproducing organisms. How might their function relate to their life span?
2. Based on the data, how are the consequences of injuries to the heart and
spinal cord similar to each other? How are they different from the
consequences of injuries to smooth muscle?