How to study anatomy & physiology: Segregate into functional compartments

Why memorizing does not work well

The problem with memorizing physiology is that your can never know it all. The accumulated knowledge, theories of physiology that describe current models of how human beings function, is collective human knowledge. Google strives to catalog it all, but even the internet does not have all of it . . .yet!

Superficial and deep muscles of the dorsal right forearm

Illustration by Alila Medical Media,



The way scientists deal with this problem of overwhelming content, is to compartmentalize their studies into specific areas. That is, they become specialists, diving deep in the sea of knowledge at one place in time. And, probably that is why anatomy and physiology are explained in terms of compartments that have specialized functions.

Anatomic vs. physiologic compartments

The major difference between anatomic and physiologic compartments is that anatomic compartments have physical boundaries and physiologic compartments are often amorphous – that is they do not have a fixed structure.

Another way of stating this is that anatomic compartments occupy space much like a room in a house occupies space. In contrast, the main characteristic of physiologic functional compartments is that they are in a state of constant motion through space and over time.

major events in the process of inflammation

Movement of Cells and Chemicals in Inflammation, illustration by Alila Medical Media,

Dividing anatomy and physiology into compartments works well to generate practical information about how humans successfully interact with their environment.

One efficiency gained by the body when using anatomical and functional compartments is that identical biological molecules can have many different jobs depending upon their location in the internal milieu. For example, competing proteins lose their ability to affect each other if there is a wall, or non permeable membrane, between them.

Much of physiology is learning about how various functional compartments maintain their integrity and communicate with each other.

Membranes separate compartments

Most anatomical compartments are separated from each other by membranes composed of fat and protein. For example, fluids of the body are divided into two compartments, fluid in cells and fluids outside cells. Cells themselves have many internal compartments. Other examples include the nucleus where the genetic code DNA is stored and mitochondria where energy from food is captured for the body’s use.

Theories of physiology strive to accurately describe possible cross talk between the body’s compartments. This is where the facts keep changing. Scientists’ best guess today about the details of these interactions will have to be tweaked when new data emerges from experiments in the near and far future.

organelles, plasma membrane, nucleus, mitochondria

Mammalian Cell Model, Mopic, via

Just so you get a feel for the various levels at which compartments are studied, the following is a partial and representative list.

A cell is a compartment. The nucleus of a cell is another compartment. There is the blood cell generating compartment of bone.

Also there are the mineral compartments of the body. For example the iron compartment of the human body includes enzymes, muscle, liver, red blood cells, and intestine.

The muscles of the arms and legs are separated into isolated compartments with their own nerves and blood supplies by dense sheets of collagen material. The lungs have functional compartments that are somewhat different from their anatomical compartments.

As you study physiology, remember that what you want to get your mind around are the boundaries of each compartment, and possible ways that communication can take place between those boundaries. If the boundary is a cell membrane, then ask what can pass through that membrane, why do the materials passing through go a particular direction, is cooperation between two or more molecules necessary for the passage of any of them to occur?

For more information on this subject you may want to read my small book “Physiology: Custom-Designed Chemistry”  You may also find other articles on this site helpful including Physiology of Cell Signaling and Ion Channels.

If you can begin to think in this way rather than trying to randomly memorize abstract theories, you will gain an understanding comparable to scientists working in physiology. There is a famous quote by Carl Sagan, Scientist, 1934-1996. “Science is a way of thinking much more than it is a body of knowledge.”

Do you have questions?

Please put your questions in the comment box or send them to me by email at I read and reply to all comments and email.

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Reece-4-S2S14-001Margaret Thompson Reece PhD, physiologist, former Senior Scientist and Laboratory Director at academic medical centers in California, New York and Massachusetts and CSO at Serometrix LLC is now CEO at Reece Biomedical Consulting LLC.

Dr. Reece is passionate about helping students, online and in person, pursue careers in life sciences. Her books “Physiology: Custom-Designed Chemistry” (2012), “Inside the Closed World of the Brain” (2015) and the workbook (2017) companion to her online course “30-Day Challenge: Craft Your Plan for Learning Physiology” are written for those new to life science. More about her books can be found at

Dr. Reece offers a free 30 minute “how-to-get-started” phone conference to students struggling with human anatomy and physiology. Schedule an appointment by email at


Compartments in Anatomy and Physiology — 5 Comments

  1. I am a writer. I post essays on my site. I have written about cancer, and I am putting together another essay and am talking about cell physiology and the need to understand it, and I would like to use your graphic drawing of a cell. May I please use this drawing, it is well done.
    Thank you. TJ

    • Margaret Thompson Reece PhDMargaret Thompson Reece PhD on said:

      Hello Timothy. I do not own the picture of the cell. I licensed it for use from an online stock photo company at They have a large number of really good anatomy photos and vectors that they license royalty free for a small fee.

  2. safi Robert on said:

    describe how molecules move within and between body compartments

    • Margaret Reece, PhDMargaret Reece, PhD on said:

      For molecules to move between compartments there must be open channels in the compartment’s membrane through which molecules can move. The design of such channels is specific for each type of molecule. For example, a potassium ion cannot pass through a membrane sodium ion channel. Much of physiology is concerned with regulation of membrane channels. The driving force on each molecule is determined by the concentration gradient of the molecule on each side of the membrane and any electrical charges in the vicinity.

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