Inside the Torso. The body's functions are conducted by organs. Each organ is a recognizable structure (for example, the heart, lungs, liver, eyes, and stomach) that performs specific functions. An organ is made of several types of tissue and therefore several types of cells (see Cells). For example, the heart (see Heart) contains muscle tissue that contracts to pump blood, fibrous tissue that makes up the heart valves, and special cells that maintain the rate and rhythm of heartbeats.