Transmission electron micrograph of smooth muscle cells

One, two or many?

Not all of your cells have a single nucleus

Most cells have a single nucleus, but not all. Some cells in adult heart muscle have two nuclei. This happens because the cells take the normal cell cycle through copying and separation of chromosomes, but do not go the whole way and divide. Why does this happen?

Skeletal muscles, such as your biceps, have very long cells with many nuclei. They form by fusion of cells with one nucleus, and their multiple nuclei may help them produce the many proteins required for muscle contraction. Another idea is that one nucleus lies dormant but triggers further cell division if the muscle gets damaged, acting as a ‘back-up’ nucleus.

By contrast, red blood cells in mammals have no nucleus. These cells are specialised for carrying oxygen and lose their nucleus during the final stage of their development, to maximise the amount of oxygen they can carry.

Lead image:

Transmission electron micrograph of smooth muscle cells.

Prof. Giorgio Gabella/Wellcome Images CC BY NC

About this resource

This resource was first published in ‘The Cell’ in February 2011 and reviewed and updated in September 2015.

Cell biology, Medicine, Health, infection and disease
The Cell
Education levels:
16–19, Continuing professional development