How does an organ level of organization relate to cells?

Cells make up every tissue, organ and organ system in the body. A cell is the smallest unit of living matter, the basic unit of life. Multicellular organisms e. g. man are organized in cells, tissues, organs and organ systems.

Cells work together in groups known as tissues. A tissue is defined as a group of similar cells working together to carry out a certain task, e. g. skin, bone, nerve and blood.

Tissue are grouped together to form organs. An organ is defined as a group of tissues that work together to carry out a certain job e. g the lungs, heart and brain. The heart contains muscle tissue, nerve tissue and blood tissue. Its job is to pump blood throughout the body.

A group of organs working together to carry out a specific function is called an organ system e. g. the Digestive system. It contains the mouth, esophagus, stomach, small and large intestines and liver.