Concept
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Tissues in Levels of Organization
![Levels of Organization](../../../../../../../../../figures.boundless-cdn.com/34138/full/nm6xzrmesccvodeoxbf1.jpg)
Levels of Organization
Molecules form cells. Cells form tissues, and tissues form organs. Organs that fulfill related functions are called organ systems. An organism is made up of interconnected organ systems.
This illustration is in the shape of a pyramid. From the top–down in this pyramid we see how molecules form cells, cells form tissues, and tissues form organs. Each level has a picture of the tissue or organ it describes. At the top of the pyramid are hydrogen and oxygen atoms. This is the smallest level and it is labeled the Chemical level. This is where atoms bond to form molecules with three-dimensional structures. The second smallest level is the Water molecule level, followed by the Cellular level. A variety of molecules combine at the Cellular level to form the fluid and organelles of a body cell, such as a smooth muscle cell. The Tissue level is built by the cells—a community of similar cells form a body tissue, such as the smooth muscle tissue used in the stomach. The Organ level is next. This is where two or more different tissues combine to form an organ. A cutaway view of the bladder shows how it contains skeletal muscle and smooth muscle. The Organ system level is the second largest level. This is where two or more organs work closely together to perform the functions of a body system. A cutaway view of the urinary tract system shows the kidney, ureter, bladder, and urethra. At the base of the pyramid is the largest level, the Organismal level. This is where the many levels and systems are coordinated to perform the functions of daily living. The illustration shows a woman drinking a glass of water.
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