What is an organ?

• A. A group of cells
• B. A system of organs
• C. A group of tissues working together
• D. The smallest unit of life

Answer: (C)

An organ is a structure made up of different tissues that work together to perform a specific function in the body. Tissues are groups of similar cells carrying out a shared role, and when several tissues join forces, they form an organ capable of carrying out more complex tasks, like pumping blood or digesting food. The heart, for example, contains muscle tissue to contract, connective tissue for support, and nervous tissue to coordinate its beating—all working together to move blood. This integrated teamwork is what defines an organ.

In contrast, a group of cells is a tissue, a system of organs is an organ system, and the smallest unit of life is a cell. So the best description is a group of tissues working together.