What does pass through the spermatic cord?

When I was an undergraduate, our anatomy teacher became quite irate with us after one test because of the particularly poor answers that she got in response to one question in particular. That question asked…

‘What passes through the spermatic cord?’

The spermatic cord is a bilateral structure related to the testes and therefore found in the lower abdomen of males only. It is so called because of its cord-like structure and appearance. In many respects it is an extension of the abdominal cavity. Each testicle develops high up in the trunk of the embryo and migrates into the scrotum. As it descends, it carries with it the vas deferens and related nerves and vessels, to put it simply. (See below.)

It appears that none of us gave a satisfactory answer to the test question—and that includes me. Furthermore, I remember being stumped when I first read the question. I had an inkling but not a complete or satisfactory answer. I also remember thinking—when our teacher told us what she had expected as an answer—how poor my attempt had been.

I remember this anecdote because of one particularly amusing comment. With a rather steely look and in a very scathing tone, our teacher told us, ‘The answer is not sperm!’ (That answer had been given by somebody and was tantamount to saying somewhat wryly, ‘I don’t know.’) This caused a general chuckle to go around the room, causing our teacher to pick on various smirking individuals and to castigate each in turn for the poor answers they had given—poor answers that she obviously found quite memorable.

So what does pass through the spermatic cord?

So as to try not to miss anything (this time), here is the result of a careful search in tabular form:

Structures within the spermatic cord:

• Vas deferens (Ductus Deferens): A tube that carries sperm from the epididymis to the ejaculatory duct.
• Arteries:
  • Testicular artery: Supplies blood to the testicle.
  • Artery of the vas deferens: A branch artery supplying the vas deferens.
  • Cremasteric artery: Supplies blood to the cremaster muscle.
• Veins:
  • Pampiniform plexus: A network of veins that surrounds the testicular artery to help regulate testicular temperature.
  • Vein of the vas deferens: Drains blood from the vas deferens.
  • Cremasteric vein: Drains blood from the cremaster muscle.
• Nerves:
  • Genital branch of the genitofemoral nerve: Innervates the cremaster muscle.
  • Sympathetic and parasympathetic nerves: Autonomic nerves that travel with the arteries to the testicles.
• Lymphatics:
  • Vessels that drain lymphatic fluid from the testes to the abdominal lymph nodes.
• Coverings of the spermatic cord:
  • Internal spermatic fascia: Derived from the transversalis fascia.
  • Cremasteric muscle and fascia: Derived from the internal oblique muscle.
  • External spermatic fascia: Derived from the external oblique aponeurosis.

To which may be added (and I don’t think we were taught this):

• Remnants of the processus vaginalis: A potential remnant of an embryonic structure may be found within the cord.

Note:
To avoid confusion, I need to point out that although there is a cremasteric artery and vein within the spermatic cord, the cremaster muscle per se is a muscular layer surrounding the spermatic cord and testes—and so not passing through the spermatic cord. It is the contraction and relaxation of this that regulates testicular temperature.

A way of thinking

Glucose plays a vital role in providing biochemical energy. We are familiar with its chemical formula C6H12O6 and may even be familiar with diagrammatic representations of its ring-like molecular structure. We may also be aware of the ratio of its atoms C:H:O being 1:2:1. In particular, the ratio of hydrogen (H) to oxygen (O) is 2:1 and that, of course, is the same as in water. Not everybody notices this until told, and then there is something of a ‘eureka’ moment. Thus, another way of thinking about the glucose molecule that is also not immediately obvious is thinking of it as 6 carbon atoms and 6 water molecules. Indeed, the chemical formula for all of the simple sugars is (CH2O)n (where n is a number greater than or equal to 3). Put simply, each sugar is a carbon atom and a water molecule n times over, depending on the sugar in question.

This in turn takes us back to where sugar comes from: plants and photosynthesis. Here in very simple terms, a molecule containing one carbon atom (carbon dioxide) and a water molecule are turned into glucose—with some oxygen left over and released into the atmosphere for us to breathe.

Embryonic problem-solving

As taught, embryology often seems a lot less dynamic than might be expected. After all, it deals with something going through rapid change. Something recognisably human is formed from a single cell in only a matter of weeks. A lot of embryology is primarily focused on how organs attain their final form. This may be better described as ‘organogenesis’. What of the intermediate or transitional forms that organs take before attaining their final forms? What is going on at a fundamental level?

Embryology can be considered as organismal problem-solving. For example, initially the embryo is formed of a ball of cells—a morula. This reaches a limiting size when it can no longer rely on the passive diffusion of nutrients, respiratory gases and waste products in and out of this simple ball. The cell mass then forms itself into a hollow ball called a blastula. As this enlarges, something different is needed to allow development to continue. Thus, the hollow ball folds in on itself to form a gastrula.

What I have been describing (albeit rather simplistically) is a series of problem-solving steps. At each transition noted above, a problem is being solved. Embryology is not just the formation of an organism as an object; it is the production of a problem-solving entity. The constant problem any embryo needs to solve is how to survive. It does this in different ways at different times depending on what it happens to be like at that time.

Know thyself - differently

The Harvard geneticist and Nobel laureate Walter Gilbert (b. 1932) described the Human Genome Project as "the ultimate answer to the commandment 'know thyself'." If so, what was it about our-selves that we have learnt?

What does a sequential knowledge of base pairs say about selves?

And…
What did we expect to learn but didn’t?
What did we think we could learn but found that we couldn’t? (And maybe can’t.)

And what did we say that we would learn, knowing that we won’t, just to make sure it got funded?

Darwin’s gaze

According to a former colleague of mine, Charles Darwin's gardener was bemused by how Darwin would stop and ponder so long over things he found in his garden. My colleague never gave chapter and verse. It was perhaps too good an anecdote to need one; it was exemplary of the man even if not entirely accurate. Now with AI, I have been able to find out more. The reference seems to be to Joseph Parslow (1812-1898), who worked as Charles Darwin's butler and gardener for many years. He often observed Darwin's intense focus on the natural world. What Parslow related was, "When he was at work in the garden, he would often be seen to stop in front of a flower, or a tree, and stand for a long time, sometimes with his hands behind his back, sometimes with his head bent forward, quite motionless, as if in a trance, absorbed in deep thought." This sentiment is often paraphrased and widely reported, including by Darwin’s family and by other members of his staff. This encapsulates Darwin's meticulous observation and profound contemplation of nature, which was a hallmark of his scientific process. He was not idly looking at flowers—as most do; he was examining them with an intense, scientific curiosity. In so doing, Darwin was responsible for changing our whole worldview, including our view of ourselves.

Second Anniversary

This post marks the second anniversary of me starting this blog. I would like to thank all those who have dropped by and read my various musings… and especially those who have been here more than once and continue to return.

This blog isn’t about me. It is not about becoming a rich and famous influencer. I keep myself as anonymous as possible and I rarely look at the number of visitors I’ve had. But when I have, I've been very gratified that people have taken an interest. So, if you are reading this, be assured of my appreciation.

As I said this time last year (and may well say again this time next year), the turn of the year provides me with a good opportunity to remind myself about what I am doing… or trying to do… or think I’m trying to do. Again my intentions remain largely unaltered, and are as stated in my first 'What to Expect' post. Hawever, that page I consider undatable depending on how the blog develops.

A few of my working practices have developed over the last year but that’s about all. In any case, these should be visible to the reader.

The aim of this blog is to share things from my former academic life that cannot be shared in any other way, lest they vanish and be lost forever. If you, the reader, can use anything from these blogs, then please do so. I would be delighted if they were to find a new lease of life elsewhere. It is not necessary to refer to this blog as your source—although it would be very nice if you did.

Reminder: I post on the 3rd, 11th, 19th, and 27th days of each month and will continue to do so. This was an additional anniversary post.

Corpuscles or Cells?

When I first did a course in anatomy and physiology and we got to the part about blood, our lecturer was quite adamant about referring to red blood corpuscles, not red blood cells. He had a reason for this: red blood corpuscles did not have nuclei, and without nuclei, they could not be properly referred to as cells per se. In the 50+ years since that lecture, in every academic and clinical setting in which I have found myself, reference has always been to red blood cells—never corpuscles.

The only other time I have heard ‘corpuscles’ referred to was when I went to listen to a talk by the mountaineer Sir Chris Bonington (b. 1934). This must have been around 1990 when he came to speak at Saint David’s Hall in Cardiff. In fact, he referred to them as ‘corpuscules’. This is not a misspelling or mispronunciation. It happens to be a now obsolete version of ‘corpuscle’—but still close enough to be the only time I’ve heard a word other than ‘red blood cell’ used. Bonington was describing what a doctor on one of his expeditions was studying and how he would be required to provide samples at different altitudes.

I remember the word ‘corpuscle’ being used in the 1960s, i.e., in my youth. Use of just the word ‘corpuscle’ immediately denoted red blood corpuscles/cells. According to the Oxford English Dictionary, the earliest known use of "red blood cell" dates from as early as 1850. The term "red blood corpuscle" was used earlier, with the first recorded use being in 1844. Looking further into the naming of blood cells, I find that the term ‘white blood corpuscles’ was also used in the mid-nineteenth century. I’ve never heard that term used, though. Why the phrase ‘white blood cell’ is used is perhaps a little puzzling when the more scientifically sounding word ‘leukocyte’ is available. (It’s three one-syllable words versus one three-syllable word. Perhaps nobody can remember whether it’s leukocyte with a ‘k’ or leukocyte with a ‘c’.)

And yet, I still like the idea of corpuscles. I like the way using the word 'corpuscle' distinguishes red blood cells from the other blood cells.

NB Here I have only been thinking of humans and the clinical setting where one does not expect to find nuclei in mature, fully formed red cells. There are animals that do have nucleated red blood cells. Fish, amphibians, reptiles and birds typically have nucleated red blood cells. In most mammals, mature red blood cells are not nucleated and also lack certain other organelles like mitochondria. This allows more space in which to pack haemoglobin. This, in turn, increases the cell's oxygen-carrying capacity.

Among vertebrates, non-nucleated red cells are unique to mammals. A notable exception within the class Mammalia is the family Camelidae (camels, llamas, and alpacas), which have elliptical red blood cells that retain a nucleus.