69 7.2 Organization of the Body

Created by CK-12 Foundation/Adapted by Christine Miller

Figure 7.2.1 Complex machines.

A Fantastic Machine

These robots were created for research or to do complex tasks, but they look like they might be fun to play with too! They are all complex machines. Think about some other, more familiar machines, such as power drills, washing machines, and lawn mowers. Each machine consists of many parts, and each part does a specific job, yet all the parts work together to perform certain functions. Many people have compared the human body to a machine, albeit an extremely complex one. Like real machines, the human body also consists of many parts that work together to perform certain functions. In this case, these parts and functions keep the organism alive. The human body may be the most fantastic machine on Earth, as you will discover when you learn more about it in this concept.

What the Human Machine Can Do

Imagine a machine that has all of the following attributes:

  • It can generate a “wind” of 166 km/hr (100 mi/hr).
  • It can relay messages faster than 400 km/hr (249 mi/hr).
  • It contains a pump that moves about a million barrels of fluid over its lifetime.
  • It has a control center that contains billions of individual components.
  • It can repair itself, if necessary.
  • It may not wear out for up to a century or more.

This machine has all of these abilities, and yet it consists mainly of water. What is it? It is the human body.

Organization of the Human Body

The human body is a complicated, highly organized structure that consists of trillions of parts that function together to achieve all the functions needed to maintain life. The biology of the human body incorporates:

  • The body’s structure, the study of which is called anatomy.
  • The body’s functioning, the study of which is called physiology.

The organization of the human body can be seen as a hierarchy of increasing size and complexity, starting at the level of atoms and molecules, and ending at the level of the entire organism, which is an individual living thing. You can see the intervening levels of organization in Figure 7.2.2. Read about the levels in the sections that follow.

 

Figure 7.2.2 This diagram shows the levels of organization of the human body, from atoms to the whole organism.

Cells

The basic units of structure and function of the human body — as in all living things — are . By the time the average person reaches adulthood, their body has an amazing 37 trillion of them! Each cell carries out basic life processes that allow the body to survive. In addition, most human cells are specialized in structure and function to carry out other specific roles. In fact, the human body may consist of as many as 200 different types of cells, each of which has a special job to do. Just a few of these different human cell types are pictured in Figure 7.2.3. These cells have obvious differences in structure that reflect their different functions. For example, nerve cells have long projections sticking out from the body of the cell. These projections help them carry electrical messages to other cells.

Figure 7.2.3 A few of the many different types of cells in the human body are illustrated here. Each type of cell is specialized for a particular role in the body.

Tissues

The next level of organization in the human body is tissues. A  is a group of connected cells that have a similar function. There are four basic types of human tissues: epithelial, muscle, nervous, and connective tissues. These four tissue types (shown in Figure 7.2.4) make up all the organs of the human body.

Figure 7.2.4 The human body contains these four types of tissues.

Organs and Organ Systems

Organs are the next level of organization of the human body. An  is a structure that consists of two or more types of tissues that work together to do the same job. Examples of human organs include the heart, brain, lungs, skin, and kidneys. Human organs are organized into organ systems, which are shown in Figure 7.2.5. An  is a group of organs that work together to carry out a complex overall function. Each organ of the system does part of the larger job.

Figure 7.2.5 The Human Organ Systems. Some of the system names shown in this illustration differ from the terminology used in this book, but the systems are the same.

 

A Well-Oiled Machine

All of the organs and organ systems of the human body normally work together like a well-oiled machine, because they are closely regulated by the nervous and endocrine systems. The nervous system controls virtually all body activities, and the endocrine system secretes hormones that help to regulate these activities. Functioning together, the organ systems supply body cells with all the substances they need and eliminate their wastes. They also keep temperature, pH, and other conditions at just the right levels to support life.

7.2 Summary

  • The human body is like an extremely complex machine. It consists of multiple parts that function together to maintain life. The biology of the human body incorporates the body’s structure (or anatomy) and the body’s functioning (or physiology).
  • The organization of the human body is a hierarchy of increasing size and complexity, starting at the level of  and , and ending at the level of the entire organism.
  •  are the level of organization above atoms and molecules, and they are the basic units of structure and function of the human body. Each cell carries out basic life functions, as well as other specific roles. Variations in cell function are generally reflected in variations in cell structure.
  • The next level of organization above cells is the . A tissue is a group of connected cells that have a similar function. There are four basic types of human tissues: epithelial, muscle, nervous, and connective tissues. These four types of tissues make up all the organs of the human body.
  • The next level of organization above tissues is the . An organ is a structure that consists of two or more types of tissues that work together to do the same job. Examples include the brain and heart.
  • Human organs are organized into organ systems. An is a group of organs that work together to carry out a complex overall function. For example, the skeletal system provides structure to the body and protects internal organs.
  • All of the organs and organ systems of the body normally work together like a well-oiled machine, because they are closely regulated by the nervous and endocrine systems.

7.2 Review Questions

  1. How is the human body like a complex machine?
  2. Describe the difference between human anatomy and human physiology.
  3. Relate cell structure to cell function, and give examples of specific cell types in the human body.
  4. Define tissue, and identify the four types of tissues that make up the human body.
  5. What is an organ? Give three examples of organs in the human body.
  6. Define organ systems. Name five examples in the human body.
  7. How is the human body regulated so all of its organs and organ systems work together?
  8. Which organ system’s function is to provide structure to the body and protect internal organs?
  9. Give one example of how the respiratory and circulatory systems work together.

7.2 Explore More

Rob Knight: How our microbes make us who we are, TED, 2015.

Computers That Think Like Humans, Fw: Thinking, 2014.

 

Attributions

Figure 7.2.1

Figure 7.2.2

101_Levels_of_Org_in_Body by OpenStax  on Wikimedia Commons is used under a CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/deed.en) licence.

Figure 7.2.3

Feature_Stem_Cell_new by OpenStax College on Wikimedia Commons is used under a CC BY 3.0 (https://creativecommons.org/licenses/by/3.0/deed.en) license.

Figure 7.2.4

Four types of tissues by CK-12 Foundation/ Zachary Wilson is used under a CC BY-NC 3.0 (https://creativecommons.org/licenses/by-nc/3.0/) license.

©CK-12 Foundation Licensed under CK-12 Foundation is licensed under Creative Commons AttributionNonCommercial 3.0 Unported (CC BY-NC 3.0) • Terms of Use • Attribution

Figure 7.2.5

Organ Systems 1 by Connexions/ OpenStax on Wikimedia Commons is used under a CC BY 3.0 (https://creativecommons.org/licenses/by/3.0/deed.en) license.

 

References

Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, April 25). Figure 1.3 Levels of Structural Organization of the Human Body [digital image]. In Anatomy and Physiology (Section 1.2). OpenStax. https://openstax.org/books/anatomy-and-physiology/pages/1-2-structural-organization-of-the-human-body

Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, April 25). Figure 1.4 Organ Systems of the Human Body [digital image]. In Anatomy and Physiology (Section 1.2). OpenStax. https://openstax.org/books/anatomy-and-physiology/pages/1-2-structural-organization-of-the-human-body 

Betts, J. G., Young, K.A., Wise, J.A., Johnson, E., Poe, B., Kruse, D.H., Korol, O., Johnson, J.E., Womble, M., DeSaix, P. (2013, April 25). Figure 3.36 Stem Cells [digital image]. In Anatomy and Physiology (Section 3.6). OpenStax. https://openstax.org/books/anatomy-and-physiology/pages/3-6-cellular-differentiation

Brainard, J/ CK-12 Foundation. (2016). Figure 4 The human body contains these four types of tissues [digital image]. In CK-12 College Human Biology (Section 9.12) [online Flexbook]. CK12.org. https://www.ck12.org/book/ck-12-college-human-biology/section/9.2/

Fw: Thinking. (2014, May 14). Computers that think like humans. YouTube. https://www.youtube.com/watch?v=I43hq13MnYM&feature=youtu.be

TED. (2015, Febuary 23). Rob Knight: How our microbes make us who we are. YouTube. https://www.youtube.com/watch?v=i-icXZ2tMRM&feature=youtu.be

 

License

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Human Biology by Christine Miller is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.

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