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It may seems stubbornly self-centered, but it does make sense to organize physiology by the major human body systems. In fact in Europe, the minimum standard and learning outcomes in physiology will soon be organized this way thanks to the Bologna process.
The previous post, this post today, and a third upcoming one all summarize my first lecture within the course “Dynamical Diseases”. The complete course will be held the first time in the winter semester 2010 at the TU Berlin. Writing these posts is part of my preparation.
In my previous post “What is physiology”, I reported on my search in various encyclopedias for an informative definition of physiology—I was really surprised how this failed.
You don’t have to read through the previous post, but you should have a first idea what physiology is: namely the “study of the functioning of living organisms”. Furthermore, “[p]hysiological processes are dynamic […] aimed at preserving a constant […] internal environment” (both citations are from the Encyclopædia Britannica). This post is mainly about living organisms and their constituent parts. The next post is about their dynamics.
Physiology is about the functioning of living organisms. It is not about, for example, form and growth of living organisms (or parts thereof). That much we understand already. Well, form and growth may be closely related to functioning but this would be another story.
Let us try to take the easy road and keep things separated. Once we have order, we can start to soften boundaries. Thus, let us ask:
I will only talk about humans. There is no good reason for this except for the self-centered stubbornness of human beings (including myself). Of course, there is also plant physiology, avian physiology, or even deep-sea diving physiology, just to name some exotic facets of this discipline. But let us start with ordinary humans.
What are the constituent parts of human beings? And keep in mind, we still only talk about functioning. Yes, I have a little toe, two actually, but as far as functioning is concerned, there is not much to say about these little guys. Frankly, they are useless. Function implies purpose.
What are my functioning parts, or yours for that matter? Sounds like a simple question, right?
Who can name the major body systems by heart? Heart, little hint here. Correct, one is the circulatory system. It consists of the heart, blood, and blood vessels. Eight more major body organ systems are missing. Come on, name them …
I am honest with you. I could not. Now I can but not before I got prepared for the upcoming lecture.
One obvious way would be to open a (human or medical) physiology text book. Although again, it is surprisingly difficult to get right to this list. There is another source, thanks to the Bologna process.
It happened that I just read the editorial of the current issue of Acta Physiologica [1]. This is the official journal of the federation of European physiological societies. (It is always a good idea to read through the main current literature once you give a course on a subject!)
In this editorial, the minimum standard and learning outcomes in physiology are addressed. Such a standard is required by the Bologna process to achieve the harmonization of the European university systems. So members of a Task Force for Education have to construct a list of objectives in physiology, which can then be used as a guiding principle for physiology curricula. While this is still work in progress, these objectives, or end-terms that is how they name it, should be organized according to the major body systems. Eleven major body systems are identified:
Of course I cross checked the list. And I found one missing major body system: the integumentary system (skin, sweat glands and stuff like that). Oups. I hope my skin still belongs to physiology and will not be sacrificed by the Bologna process.
If you read carefully till here, you noticed that I said above that there are nine major body organ systems. Now Acta Physiologica published a list of eleven plus one that is missing. There seem to be three too many.
Well, the water and salt homeostasis system, metabolism, and thermoregulation are not really related to organs. Actually, neither is the endocrine system related to (only) one organ. Moreover, metabolism could also be placed into the field of biochemsitry. But as I said, let us keep it simple. All these are functioning system of a human (and many more living organisms).
So the picture seems to me that we have eight major body organ systems, one multi-organ system and three major body systems that do not relate to organs explicitly. All are functioning systems and therefore are in the center of interest of physiologists.
I don’t know about you, but I learned enough today. Only two more inter-related remarks.
First, well, you might correctly think this is heavily biased towards human physiology. That is true, but since this list is meant to be for physiology learing outcome within a medical curriculum, I guess this list is complete (except for the skin).
In North America, students can major in physiology, but—to the best of my knowledge—in Germany you either learn physiology as a medical student or as a biology student. There is no master in Physiology in Germany, yet, or is there?
Second, I got most information from the Encyclopædia Britannica and heavily using Amazons Look Inside feature on many Physiology text books. Furthermore, to defend, at least partly, the honor of Wikipedia the major body systems will also be found there. In the article on Human Physiology. If you think it would be too self-centered to have these systems being mentioned in the main article, that is ok with me. Yet the water and salt homeostasis system, metabolism, and thermoregulation, that is, the three non-organ systems are missing. Instead, you can read there that the immune system is part of physiology. This, although there is some logic behind it, is now one step too simple.
Luc Snoeckx, head of the Task Force for Education that is to construct the list of objectives in physiology, wrote me an email with the following explaination on whether the integumentary system is missing and if major body systems are organ systems:
Indeed, we did not consider the integumentum as a separate “organ” but preferred to make it part of the ‘functional’ systems Nervous system and Thermoregulation. It is a choice, and I agree that it is defendable to put all the functions of the skin under one denominator. Your second remark is also correct if you consider the organs as anatomical organs, which we did not. We preferred the functional organs, and as such the approach of metabolism, homeostasis, and thermoregulation can be considered as “functional”, more than organs, which is agreed upon.
[1] Luc Snoeckx, Minimum standard and learning outcomes in physiology required by the Bologna process: the Federation of European Physiological Societies end-terms of physiology in a medical curriculum, Acta Physiologica, 200:1-2, 2010.
