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How do tissues work together to form organs?

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Diagram explaining ATP's role in powering cellular activities, with arrows showing ATP produced by mitochondria, chloroplasts, and glycolysis, and used for making biomolecules, transporting substances, and driving energy-requiring processes; includes a structural diagram of ATP with labeled adenine, ribose, and phosphate groups. — Physiology Adenosine triphosphate (ATP) is the power source of many biochemical reactions. It is produced in the cell structures and system listed at the left to energize the important life processes listed on the right. An abbreviated chemical formula of the structure of ATP is also shown. The two high-energy P―O―P bonds are responsible for its power.

In biology, an organ is defined as a distinct structural and functional unit formed by the aggregation of different types of tissues. These tissues work together in a coordinated manner to perform specific physiological tasks necessary for the organism's survival.1

For example, the heart is an organ composed of all four primary classes of animal tissues: epithelial, muscle, nerve, and connective tissues. By integrating these tissues, the heart functions as a pump to circulate blood throughout the body.1

The organization of these tissues is supported by the extracellular matrix, a complex material that fills the space between cells. This matrix provides structural integrity and serves as a substrate for cell attachment, allowing tissues to maintain their shape and function within the organ. Ultimately, these organs act as components of larger organ systems, which function as integrated units to sustain life processes such as respiration, digestion, and circulation.231