Lungs and Living Forever

There is a general assumption that if only we could make the cells of our bodies live forever, then so would we. Only cancerous cells are known to divide indefinitely, but groups of such cells do not form structures that are architecturally as sophisticated as the organs ordinarily found in the body. The architecture of the organs is important to the processes these organs perform. So is the behaviour of cells forming these structures. Some cells exhibit quite innocent behaviours that mean that even if cells were immortal, the innate mortality of the organism cannot be avoided.

I am thinking particularly of the lungs.

Even though the lungs are enclosed within the thorax, they are on the front line when it comes to intimate contact with the outside world. We cough out dust, but not all of it. Although they have what might be described as ‘dust-catching’ mechanisms, it is impossible for all dust to be out. It is inevitable that some dust particles will enter deep into the airways.

(Indeed, I remember a cadaver that we were dissecting many years ago. It must have been that of a South Wales miner who, judging from his age, may well have been down the pit in the 1960s or 1970s. His lungs were of the purest, shiniest black that one could imagine. It was as if they had been sculpted from a block of pure anthracite, except that they were soft (even allowing for the embalming process).

The lungs have a mechanism for dealing with those particles that are not coughed out or caught. This mechanism is to wrap them up and form a fibrous barrier around them. Sometimes these packages may even be seen on a chest radiograph – especially if they calcify.

This mechanism has a downside. The process of fibrosis leads to a local reduction in the elasticity of the lungs. This, in turn, makes it more difficult for other particles to be removed and fibrosis progresses. It is conceivable that if we lived long enough, eventually the whole lung would become fibrosed. Certainly, breathing would become increasingly less efficient. If living forever were merely a matter of cells becoming immortal, this (normal) behaviour of lung cells would eventually lead to them becoming unable to sustain life. To prolong life, a lung transplant would be necessary.

The following illustration may add further insight.

From: Roberts, F., & MacDuff, (Eds.). (2018). Pathology Illustrated (8th ed.). Edinburgh. Elsevier.

Gene thinking

The use of the word gene has influenced how we think and speak about heredity. Too often we hear of a ‘gene for this’ and a ‘gene for that’. Given a name, a gene has become a specific thing. The word was first coined in 1909 by Wilhelm Johannsen (1857-1927). In his seminal work, Gregor Mendel (1822-1884) referred only to 'determinants of heredity'. When Johannes coined the term, he had no improved evidence of what the ‘determinants of heredity’ were. He did not know whether they were singular, multiple, situated in one place or distributed and working in concert. Whereas a gene is something specific, a determinant can be an array, a set of factors or even a programme of contributing factors. Mendel’s terminology may still be the more accurate description. At least we can choose to think in Mendel’s terms if the rest of the world uses Johannsen’s ‘shorthand’ term.

Where do breasts belong? (1)

Prologue
In the title for this post, I am using anatomical speech. Breasts come in pairs, of course, so talking of the breast may seem odd. But as with every paired organ in the body, anatomical speech uses the singular. I don’t know why. Talking of ‘each breast’ instead of ‘the breast’ makes sense. In each of the paired organs, the same processes take place irrespective of whether they happen to be on the left or right. And referring to ‘each breast’ also uses the same number of syllables as ‘the breast.’

What I really wanted to focus on was asking to which of the body systems (or physiological systems) does the/each breast belong. As an old professor of mine once put it—quite accurately—the mammary glands (which, with their associated fat, form the basis for the roundness of breasts) are merely modified sweat glands. That makes the milk mammals produce a form of sweat—albeit in a highly modified and nutritious form. (A comparison is worth making with the duck-billed platypus, where the infant licks milky secretions from an area of its mother’s skin rather than from teats or nipples.) Thus, breasts seem to belong quite reasonably to the integumentary system. That, after all, is the system that concentrates on the layers of the skin and associated structures: hair, nails, and the oil and sweat glands.

However, breasts also play a role in reproduction. Without their secretions, offspring would not be able to survive long after birth. Although humans have access to alternatives to breast milk, other mammals do not. So functioning mammary tissue is essential for the survival of offspring. Indeed, can we really call it reproduction or consider reproduction to have properly taken place without some way of ensuring the viability of the offspring? Especially in altricial species such as our own.

Human breasts are also described as secondary sexual characteristics. They develop during puberty in readiness for the reproductive phase in the human life cycle. In so doing, they are also signals of sexual maturity. In this respect, they are also involved in sexual attraction. Thus, they are more than just modified sweat glands.

To return to my original question, does the breast belong to the integumentary system or the reproductive system? Or does the breast overlap with both systems? Or is it an organ not fitting into the current way of defining physiological systems? If this is the case, does this ask questions of the way in which the physiological systems are currently classified? If so, we must consider other ways in which we might conceptualize the human body as a material entity.

From 'Adventures in Human Being'

In Gavin Francis’ book Adventures in Human Being, the author mentions the novel Zeno’s Conscience by the German-Italian writer Italo Svevo (1861-1928). In that novel, the main character, a hypochondriac businessman called Zeno, meets an old school friend. This friend is suffering from severe arthritis. Discussion moves to how, when walking briskly, each step might take less than a second and yet involve the action of no fewer than fifty-four muscles. Zeno finds this rather shocking and turns his attention inward, hoping to sense each one of those muscles in action. This does him little good. It does not give him a greater understanding of his body or sense of his being. In fact, it becomes counterproductive as walking becomes more difficult for him.

The story recognises how, in order to perform certain complex actions, it is not necessary for us to be consciously aware of every muscle contraction we make. Nor, for that matter, every muscle relaxation made. Most of our movements are done without careful thought or consideration. As I have typed this, I have been thinking about a number of different things, none of them being about which finger to put on what key or the order in which those actions must take place. (Witness the many typos I always need to correct.) Chameleons, an old professor once suggested, have their distinctive way of moving because, lacking a highly developed cerebellum, they need to move more deliberately. The cerebellum stores the information – some might call this a set of programmes – for all the movements we make. When we need to make a movement, we do not have to think much about it. We decide to move and subconsciously call upon the cerebellum’s involvement. In effect, the programme held there is run, and the movement is results.

What would it be like to be a chameleon? If my old professor was correct, it is doubtful whether I could think and type at the same time. I would have to think more carefully about every finger movement. This would surely detract from what I am thinking about. (It’s a good job I don’t chew gum!)

We tend to think of movement primarily in terms of muscle contraction. However, to make a movement, a whole repertoire of relaxations as well as contractions must take place in a highly coordinated way. A contraction may even be isometric in that it may occur without a change in length taking place. By becoming taut, that muscle provides a stabilising effect. There is much more to walking than Zeno was told, which is perhaps lucky for him.

Being smarter than 'phones

Biological knowledge must include understanding; it must be more than can be called up on a smartphone.

This note I made before the advent of AI. I am a great fan of AI. It can help us understand biology, especially if the responses given prompt us to ask better questions (aka prompts*).

* I wonder if, at least in some people's minds, the word 'question' will come to be replaced by the word 'prompt'.

Anatomical Junctions

The previous post had little, if anything, to do with the human body and more to do with South London's railways. So, here is a post about genuinely named anatomical junctions. I provide it by way of compensation and recompense for the previous post.

The following is a list of terms containing the word 'junction.' I have limited it to structures larger than cell size and provided a brief description for each:

• Atrioventricular Junction: The junction between the atria and ventricles of the heart, where the heart valves and conducting system are located.
• Costochondral Junction: The junction between the ribs and their costal cartilage, which allows for flexibility in the rib cage.
• Myotendinous Junction: The junction between a muscle and its tendon, where the force of muscle contraction is transmitted.
• Neurovascular Junction: The junction between nerves and blood vessels, often referring to points where nerves and vessels run close together.
• Oesophagogastric Junction: The junction between the oesophagus and the stomach, where the lining of the digestive tract changes.
• Rectosigmoid Junction: The junction between the rectum and the sigmoid colon, a transition point in the large intestine.
• Sacrococcygeal Junction: The junction between the sacrum and the coccyx, a slightly movable joint.
• Sternoclavicular Junction: The junction between the sternum (breastbone) and the clavicle (collarbone), a key joint for shoulder movement.
• Vesicourethral Junction: The junction between the bladder and the urethra, controlling the flow of urine.

I cannot vouch for how exhaustive this list may be. My online searches (including the use of AI) yielded just these. I do not remember the term 'junction' being used frequently. Indeed, only a few of those above (such as the costochondral junction and the rectosigmoid junction) were ever commonplace. Rather, the sacrococcygeal junction was more often referred to as the sacrococcygeal joint and the sternoclavicular junction as the sternoclavicular joint.

At every meeting of two veins, there is a junction. (Following the direction of blood flow, veins DO NOT branch.) Where named, a venous junction seems to reflect a need for clinical rather than anatomical precision. I was never taught a litany on named venous junctions.

Eponyms 2 - Poupart's Junction

I seem to be starting each month with something about eponyms. At least this time it gets a new number. That is because it is quite different from what has gone before when it comes to eponyms and to anything else for that matter.

Poupart’s ligament is not the only eponymous use of the name. Upon reading Richard Gordon’s Doctor in Love (1957) recently, I found this amusing story.

During a viva voce examination, Gordon is asked

“You are familiar with Poupart’s ligament?” asked the Professor, as we got on to hernias.
Of course, sir.”
“Ah! But where is Poupart’s junction?”
For a second I felt panic. This was an anatomical feature I’d never heard of.
“It’s the next station to Clapham Junction,” [the professor] said with a chuckle.

This geographical detail is indeed true—see the map below. However, I cannot vouch for the veracity of the rest of Doctor in Love (including whether this viva voce examination ever did take place).

FYI Poupart’s Junction is not named after the Poupart discussed in a previous post. It is named instead after the market gardener Samuel Poupart (b. 1807), who once owned a farm on land that is now part of the nearby Shaftesbury Park Estate. In particular, see the section on its history. (And if you really want to know more go here.)

[Source - https://upload.wikimedia.org/wikipedia/commons/1/1d/Clapham_Junction%2C_Stewarts_Lane%2C_Lavender_Hill_%26_Longhedge_RJD_17.jpg ]

‘POUPART’S JN.’ is written at an oblique angle, immediately to the left of the ‘LONGHEDGE’ that appears towards the middle of the map.