Taller by the Minute

What am I looking at?

This is a composite image (mirrored vertically) of a stained cross section from a developing human bone. You can see the epiphyseal growth plate in blue (1); there’s one located near the end of each of our long bones. The porous red and purple area at the center of the image is spongy bone (2) – the soft inner core of our bones. The outermost layer of our bones, known as compact bone, is the hardest, densest layer (3).

Biology in the background

During development, bones start out as cartilage – a tough but flexible tissue that begins to harden into true bone as an organism grows. However, even after bones harden, they continue to grow. They do so at specialized areas called growth plates, which continue to contain cartilage until the organism stops growing, as it nears adulthood, and then the growth plates harden into bone as well.

It is these epiphyseal growth plates at ends of our long bones that are responsible for lengthening our bones as they grow. Since the length of the long bones is the main determining factor in an organism’s ultimate height, these growth plates are major players in determining how tall any given human becomes.

The growth plates in this image are about 100 micrometers thick, or slightly thicker than a human hair.

Technique

This image was created using a form of light microscopy called brightfield illumination.