What are made up of different types of tissues?

Organs are composed of different types of tissues that work together to perform specific functions within the body. Tissues are groups of similar cells that carry out particular tasks, and there are four primary tissue types: epithelial, connective, muscle, and nervous tissue. An organ, such as the heart or liver, contains a mixture of these tissues that collaborate to fulfill the organ's role. For instance, the heart consists of cardiac muscle tissue for pumping blood, connective tissue for structure, and epithelial tissue lining the chambers.

In contrast, cells are the basic units of life and do not combine with other types to form structures beyond themselves. Systems refer to larger groups of organs that work together to perform broad functions, but on their own, they do not consist of varying tissue types. Molecules are even more basic and are made up of atoms; they do not have the complexity of different tissue types. Hence, the concept of organs being made up of different tissues is fundamental to understanding anatomy and physiology.