Anomalous lobes in the lungs

As part of an anatomy course, a group of four medical students had been dissecting the thorax of a cadaver. It had taken them a few weeks as they progressed step-by-step from the skin to a now almost empty chest cavity. The heart remained in place for the next phase of dissection but the lungs were not removed.

Upon completion of this stage in the process, the students were required to be assessed by a demonstrator who would check on their learning. The demonstrator for that group of students was me. I was duly called over to quiz them. What met me was an open, lung-less cavity with the anterior wall of the chest folded back. The lungs lay elsewhere on the dissecting table.

'Before we start,' I said, 'let's put everything back into its original place so we can go through what you've done step by step.' The students picked up the lungs, quickly looked at them and squeezed them into their respective cavities. Or so they thought.

The left and right lungs are not exact mirror images of each other. For a start, the heart is situated slightly to the left and so impinges upon the left lung. For this reason - or so it is usually stated - the left lung has just two lobes, whereas the right has three. (Whether that is the complete explanation, I do not know. Indeed, what follows may suggest that the explanation lies elsewhere.)

What the students did, before putting the lungs back into the chest, was count the number of lobes: two means left, three means right. The lungs being the spongy compliant organs could be squeezed in fairly easily. But then, lungs can be squeezed into almost any space - even those from embalmed cadavers.

With this body, I could tell, things were not as expected. The left lung had three lobes (not two); the right lung had two lobes (not three). The opposite of what the students had expected; the opposite of what they had been taught and what they had read. By simply counting the lobes the students had proceeded to squeeze each lung, into a cavity of the wrong shape and size - and facing backwards!

There are more accurate ways of determining to which side a lung belongs. These do not require the number of lobes to be counted. There are a number of clearly visible surface characteristics which allows the lung to be orientated in space.

I pointed out the error to the students and passed it off lightly. We were able to laugh about it and started again. The students passed the quiz. They were serious-minded people who had applied themselves diligently to their task. I am sure that their error was a useful learning experience. However, it was actually quite a grave mistake. It would even have resulted in failure under stricter conditions.

Significantly, this was the first time any of those students had realised this anomaly about their cadaver. None of them had noticed when the lungs were first removed that the number of lobes was atypical. How could they have missed something so glaringly obvious?

Being diligent students may have been their problem. They had followed the dissecting instructions meticulously. They had removed the lungs and put them aside for dissection later as instructed. They had proceeded to dissect the empty cavities left behind before focusing on the lungs as separate organs. When it came to examining the lungs, there was, as described one with two and one with three lobes. They had assumed - as stated above - two means left, three means right.

Were the students really at fault? They were following instructions; they were doing what they were required to do. They were not required to explore the human body or discover things about it for themselves. They were put into an environment in which instructions were to be followed. It may be little wonder that they slipped up. They were learning the contents of a prescribed syllabus. The cadaver they used was a means of simply backing this up when a spirit of discovery might have been preferable.

Up to date textbooks

As students go off to college or university - some for the first time - they should take heed! Students need to be wary of the latest editions of textbooks - especially given how much textbooks cost. Students should always ask whether 'latest edition' means the same as 'up to date'. The assumption is that this is the case - but this assumption is wrong! Students often feel obliged to buy the latest edition of a textbook lest they miss out on some vital bit of information missing from an older ‘out of date’ edition. But is passing or failing ever down to just one bit of information present or absent from a textbook? 

Some textbooks recommended for the courses with which I have been associated have gone through new editions three or four times in as many years! No academic discipline can claim to have been revised or updated that often - let alone in such a brief space of time.

Textbooks may change rapidly but academic disciplines change very slowing - and some seem to change rarely. Some fundamental details never change. What does change is a textbook’s layout and presentation; how publishers what it to look. Headings (and typesettings) may change; diagrams and tables may be added, removed or modified; page numbers may change accordingly. None of this reflects a major change in learning or fundamental course content. If any ‘major’ intellectual development did occur between editions it would be big news. Lecturers would certainly know about it and change their teaching material to suit. They would even emphasise the fact. (What lecturer would not want to be seen discoursing authoritatively on the latest big discovery?)

So beware before you spend. Ask yourself, Why do academic libraries keep old editions of books if they are always so flawed? Why are previous editions of a textbook not all pulped the moment a new edition appears? Why are they sometimes donated to poorer, third countries? When we ask questions like these, we see things quite differently.

The Schematic Circulation of the Blood (2)

Here is another diagram showing the circulation of the blood. I have a number of these to show. What I want to do is show how different one of the most commonly used illustrations found in textbooks of anatomy and physiology can be. Other than that, I am making no other judgements about the quality of those diagrams. (Accordingly, I am not giving bibliographic details or otherwise indicating their source.)

To see other diagrams in this series, click the label 'The Circulation' below or in the margin to the right.

Some diagrams may be better viewed downloaded.

A headache when passing water

A radiologist once told me what at first sight seemed to be a very strange story. It was about a man who went to see his GP because every time that he emptied his bladder he got a terrible headache. There is no medical condition that presents in this way and so the GP was rather puzzled. As was I. There is no obvious 'cause-and-effect' type pathological process that could explain what was going on. The man was duly sent for tests at the local hospital.

In brief, what they found was not one but two pathological processes operating at the same time. Firstly, the man had a condition called hydronephrosis. This literally means a 'water-logged kidney'. This causes the kidney to become swollen with the urine it produces. This swelling can be relieved by passing that urine. However, hydronephrosis is a well-known condition and headaches when passing urine is not one of them. So, to explain the man’s headaches, there must be more.

Upon further examination, it was found that the man also had a tumour of one of his adrenal glands. (There are two - one situated above each kidney, hence the name.) This tumour was of an adrenaline producing variety. Again, these are quite well known and the man's symptoms were, again, not fully explained.

When both diagnoses were put together the picture became clear. The adrenal tumour was of the adrenal gland that sat upon the water-logged kidney. When that kidney was swollen, it pressed on the adrenal gland and its tumour squeezing it against the diaphragm and posterior abdominal wall. This impeded the venous drainage of the adrenal gland. Thus, a reservoir of adrenaline produced by the tumour built up inside the gland. When, upon urination, the swelling of the kidney was alleviated, so too was the squeezing of the adrenal gland. Thus, a big rush of adrenaline was released. That immediately sent the man's blood pressure rocketing giving him his post-urination headache.

Even though a clear chain of events could ultimately be determined, this is not a simple story of cause-and-effect. The urinary system is involved, as is the endocrine system (since that system includes the adrenal gland). So too is the cardiovascular system. It was the pressure in that system that rose upon the release of the stored-up adrenaline. Then again, the nervous system was also involved. It was there that the headache was both generated and experienced. It came about due to the pressure in the arteries within the brain. Then there would have been the other effects of a large dose of adrenaline elsewhere in the man's body which were not immediately obvious.

This, then is really a story about what happened to a whole organism - and to a person. It is not simply a clinical case study about pathophysiological details but an example of the integrated nature of ourselves as organisms. Indeed, all case studies are ultimately really stories about persons.