Organs are grouped into functionally related associations known as organ systems.

Here's why:

* Organs: These are structures made of different tissues that work together to perform a specific function. For example, the heart is an organ that pumps blood.

* Organ Systems: These are groups of organs that cooperate to carry out a major bodily function. For example, the cardiovascular system is an organ system that includes the heart, blood vessels, and blood.

Let me know if you'd like more examples of organ systems!