Organization Levels of the Body

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Chapter: Anatomy and Physiology for Health Professionals: Levels of Organization : Introduction to Human Anatomy and Physiology

1. Describe the major levels of organization of the body. 2. Identify the tissue level and the organ system level.

Organization Levels of the Body

Organization Levels of the Body

Every body structure is made up of smaller structures, which are, likewise, made up of even smaller components. Chemicals compose every material found in the human body. They contain microscopic atoms combined into structures known as molecules. Many molecules may be combined into macromolecules. These macromolecules, in turn, form organelles, which help to complete the intended functions of a cell, the basic unit of both structure and function inthe human body.

Cells are microscopic structures that can vary in size, shape, and function. Cells are grouped together to form tissues, which, in turn, are grouped together to form organs. Groups of similarly functioning organs form organ systems, which then combine to form a living organism (FIGURE 1-1). Body parts are organized into different levels of complexity, including the atomiclevel, molecular level, and cellular level. Atoms are themost simple in structure, with complexity increasing in molecules, organelles, tissues, and organs.

At tissue level, the tissues work together and perform one or more specificfunctions. For example, cardiac muscle cells interact within the heart with other types of cells. They also interact with extracellular materials, forming cardiac muscle tissue. At the organ level, the tissues of an organ work together, performing several functions. For example, layers of cardiac muscle tissue work with connective tissue to form most of the wall of the heart, which is a hollow, three dimensional organ. At the organ system level, groups of organs inter-act and perform particular functions. For example, each contraction of the heart pushes blood into the blood vessel network. The heart, along with the blood and blood vessels, comprise the cardiovascular system. This is one of the 11 organ systems of the human body.


1. Describe the major levels of organization of the body.

2. Identify the tissue level and the organ system level.

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