The adaptive immune system is highly complex and specific. In this article we focus on T cells, and discuss their development, their different functions, and what happens when they don't function ...

Hormones are chemical messengers that regulate many functions in the body, including sleep, appetite, libido, and mood. Learn more here.

For example, your ribs protect your heart and lungs, and your skull protects your brain. Producing your blood cells. Certain types of bones make your platelets, red blood cells, and white blood cells.