If your son is ten years or older, he is likely noticing changes happening in his body. Puberty is the time when testosterone begins to have obvious effects in his skin, muscles, and of course, his reproductive structures.

This anatomy figure from my book, I’m a Boy, Hormones!, shows where testosterone is produced in your son’s reproductive system.

I’m a Boy, Hormones!

Notice the large round circles of cells in this figure. The small blue circles are sperm forming. The round blue cells under the yellow covering in each tube change as they are pushed toward the white space in the center of the tube. By the time the round cells arrive at the white space, they have changed their structure and now they look like sperm.

Outside of the large round circle of sperm-producing machines, are patches of pink cells. These cells produce testosterone. The pink cells are told by the brain to make different levels of testosterone based on what the body needs. Testosterone goes into the blood and travels all around the body to have its effects.