Body systems are comprised of organs. What are organs made up of?

Organs are intricate structures that perform specific functions within the body, and they are primarily made up of tissues. Tissues are groups of similar cells that work together to carry out a particular task. For example, muscle tissue enables movement, while epithelial tissue covers surfaces and lines cavities. Different types of tissues—such as connective, nervous, muscle, and epithelial tissue—come together to form an organ, allowing it to perform its function in conjunction with other organs in a body system.

The other options do not accurately describe the composition of organs. Cells, while fundamental building blocks of tissues, do not constitute organs directly. Organisms refers to entire living entities, encompassing multiple systems, organs, and tissues, thus is too broad. Lastly, systems are higher-level structures that comprise multiple organs working together, which also does not relate directly to the makeup of an organ itself. Therefore, understanding that organs are formed from tissues is key to grasping basic human anatomy and physiology.