Hierarchical Levels of
Anatomy
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There are six hierarchical levels of anatomy and physiology.
(1) Chemical level (2) Cellular level (3) Tissue level (4) Organ level (5) Organ system level (6) Organism level |
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The Chemical Level
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ATOMS - What's the MATTER?
All matter in the universe as we know it, is made up of atoms. It is for this reason that we define the atom as the fundamental unit of matter. An atom is made up of subatomic particles. The nucleus (or center) of the atom is made up of one or more positively charged subatomic particles called protons and uncharged subatomic particles called neutrons. Almost all of the mass of the atom is located in the nucleus. Electrons "orbit" the nucleus of the atom. The electron(s) that are located on the outermost portion of the atom can participate in chemical reactions and can create bonds with other atoms. MOLECULES
When an atom forms a bond with one or more other atoms, it is called a molecule. A molecule is made up of one or more atoms. Sometimes these molecules are small and simple. We can take oxygen as an example. Oxygen is a gas that is made up of simply 2 oxygen molecules that are bound together (02). Some molecules consist of thousands of atoms (macromolecules) like DNA and proteins. |
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Animated GIF courtesy of http://giphy.com/gifs/black-and-white-life-99XYfEEF2QV7a
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The Cellular Level The cell is the fundamental unit of life. All living things are made up of one or more cells. You came from just one cell! You started out as a zygote, which is a fertilized egg. From there you began to undergo rapid cellular division (see GIF) which lead to the exponential growth that made the cute, bouncing baby that was YOU! Pretty amazing!
Cells and their surroundings are made up of molecules. It takes about 100 trillion atoms to make a typical cell. Proteins, lipids, carbohydrates and nucleic acids are arguably the 4 most important molecules for the cell, and for life in general. |
The Tissue Level
Cells of similar types come together to form tissues. A TISSUE is a group of two or more cells (of similar function or origin) that come together to perform a common function.
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Tissue level:
There are 4 types of tissues
Muscle Tissue
The body contains three types of muscle tissue: (a) skeletal muscle, (b) smooth muscle, and (c) cardiac muscle. From top, LM × 1600, LM × 1600, LM × 1600
. (Micrographs provided by the Regents of University of Michigan Medical School © 2012) 
By OpenStax College - Anatomy & Physiology, Connexions Web site. http://cnx.org/content/col11496/1.6/, Jun 19, 2013., CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=30015032
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Epithelial and Connective Tissue
By Rollroboter - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=32009339
Nervous Tissue
CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=657559
Cross Section of Peripheral Nervous Tissue |
The Organ Level
An organ is a discrete structure made up of multiple tissue types that work together as a functional unit for the body. The major organs of the human body are listed and illustrated below. Organs that are found anywhere in the ventral cavity, can be referred to as visceral organs. The word "visceral" or "viscera" refers specifically to the internal organs that lie in the thoracic or abdominal regions of the body. organs of the body, specifically those within the chest (as the heart or lungs) or abdomen (as the liver, pancreas or intestines). In a figurative sense, something "visceral" is felt "deep down."
The Organ System Level
There 11 Organ Systems of the Human Body. An organ system is a group of organs and associated structures that perform a specific function in the body. The example shown here is the cardiovascular system, showing blood vessels, blood, and the heart.
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The Organism Level
The level of the organism looks at how all of the anatomical structure of body work together to provide all of the necessary function for life.
