Saturday, April 14, 2007

Anatomy of skin

I am currently involved in an anatomy project at UBC, a piece that will help me fulfill a dream I have to help the relatively small and far from earth-shaking world of manual therapy finally make sense. My only ambition in life at this point is to be part of the solution instead of part of the problem. (I'm copying and pasting most of this blog from comments I made on a discussion forum thread, which is why it reads a bit choppy.)

This is from day 1, on April 3:

What a day. I finally got to set foot in an anatomy lab today, after a few frustrating years trying, finally getting an appointment set up, only to have the plan delayed in February because of a building problem. But today was the day.

The room was enormous and brightly lit, new white walls and gleaming tiles, 44 gurneys, 4 across and 11 down, each with enough space around it for a cluster of ten or so people, one long wall filled with blackboard. Cadavers lying horizontal, each dressed in a bright blue body bag. Not much smell at all.

At 9:30 AM I was given a bright green coat, gloves, a tray, some tools, shown how to use them, then left on my own to look at skin from the inside out. The hours flew by - suddenly it was 1 PM and I had to stop for the day. I realized I'd been standing on concrete and working the entire time with no rests or bathroom breaks and it never even registered, although maybe it will tomorrow... What an unbelievable opportunity to see layers and layers and layers.. all that slightly stretchy filamentous stuff in there holding everything together, wafting this way and that way, to sink through them with my own fingers. I really can say I've done "myofascial release".

My guy (I started referring to him in my head as "my guy") was old, had had an IV, had had a pacemaker at some point, had been dissected quite a bit already, but there was still one arm on him that had not been examined yet. An arm for me, My Guy's arm, still full of nerves.

The Dr. in charge unveiled My Guy's arm, pulled it out of the bag, leaned on it several times to externally rotate it, and supinate it, then showed me how to use the scalpel and change the blade, use probe, scissors, forceps, etc, told me where she would be if I needed anything, and said go for it. I asked her if there was anything wrong I could possibly do, i.e., wreck, and she said no. She gave me a whole arm to work on. Make mistakes on without worrying about how precious My Guy was. Unbelievable opportunity. So I went ahead. I'm sure it's not surgical quality dissecting I did this very first time, but I sure learned a pile of stuff.

I followed the musculocutaneous nerve (very big, unmistakable) from behind the bicep to the lateral side of the forearm, inspecting the big bruise and clotted blood that had been left by some long ago IV needle along the way. The way nerve wrapped under and over vessel was interesting. Where they connected (to feed each other, I guess) was interesting. I found several small cutaneous branches that headed up into skin - they looked like they come up to skin in bunches every couple inches.

I really had no clue until today just how thick skin is. This was an old guy, not obese at all but a good size male, with a regular size male arm. The skin was a good half inch thick in places, I kid you not. Lots of fat right in it. It slid around on the deep fascia layer, well, not as much as it does on a live person, of course, but there was still motion between layers. I prodded and squeezed the fat away from the network of neural tissue I was studying, managing to get a good sense of how three dimensional it is, how tough the outermost layer is, how tight the nerves are attached to the underside, how little they are by the time they get out that far, managing to break a few in the process alas...

I was down by the wrist by now, so I cut a square of (much thinner) skin about 2.5 by 2.5 inches on the back of the hand, and blunt probed it loose, in order to look under it to see the skin ligaments. There were several under there, permitting movement in all directions.

Going back up, I managed to get the biceps free from all sides. I could hardly believe how small it looked in this big arm, only about an inch and a half in diameter. Skin with all its fat takes up an huge amount of space, more than I ever expected.

I found the ulnar(?) nerve from axilla to part way down the arm, but couldn't really get at the medial side of the elbow. Maybe next time - I get to go again. The skin over the deltoid zone was very interesting, very thick, full of physiological webbing/tubing/neural structure, but I haven't found the axillary nerve yet.

At 1 PM, the Dr. in charge came back in and showed me how to wrap up My Guy's arm, put it into a plastic bag, spray it with solution right into the bag to keep it fresh, put a sign on it saying "don't touch", then put it all back in the big blue bag and zip him up 'til next time, scheduled for April 12. Can't wait for the next episode.

Part of the reason that it took me so long to get into an anatomy lab was the difficulty convincing anyone that a PT could actually be interested in something other than muscles&joints. There are workshops/refreshers from time to time here, but it's always the "knee", etc. Luckily, the Dr. in charge (who used to be a PT once upon a time) gave me an hour long interview, and listened. She really listened. It also didn't hurt that I sent her the skin ligaments article, which impressed her no end. I finally convinced her that what I wanted to look at was OK, and that I wasn't a nut case. What does skin have to do with anything? Oh.. just about everything..

Nerves are white and round and tough. Quite big. The musculocutaneous nerve is about the width of a printer cable. The vascular structures are darker and more flattened. The cutaneous branches are numerous and quite wispy, but tougher than the fascial wisps that they are embedded within. I got fairly adept at seeing the difference, checked with the instructor who came in to check on how things were going once, who said good, assured me that everything I was finding was nerve. When one inserts a probe under some fascia and lifts it up from behind, it becomes clear, like thick wet saran wrap. There's a certain resistance to it. When neural filaments are embedded within, they provide a bit more resistance, and if you look close they look like white threads inside the rest, more visibility. I spent a whole lot of time carefully breaking everything that was not nerve. Then when I lifted the big skin flap, it was still attached by the cutaneous nerves, obliquely running from the nerve to skin. They were lifted clear of the arm and I could see their pattern. So very cool.

There was never any focus on any of this cutaneous innervation when I was in first year, the only year we studied anatomy. All we had were dried up shreds from whatever was left after the med students had done all the dissecting. A big bone and some sliced up muscle attached that we were supposed to try and figure out how it went together, how it would look if it hadn't been cut up. No skin, and certainly no cutaneous nerves on anything, all useful bits burned off by chemicals. And certainly the smell used to be much much worse.

From April 12:

Today I was able to get back into the lab to visit My Guy's Arm. I went armed this time with a bunch of drawing supplies, and drawings I've already done to show the Lab Director. She liked the way the artwork was coming along.

Into the lab we went, and she took a look at the work I'd done last week. It was good, she said. As we peeled the cutaneous layer away from the lateral arm, the lateral cutaneous nerve of the forearm was pulled taut by all the cutaneous twigs and skin ligaments through which they convey, outward and obliquely. Isn't that interesting, she remarked. Usually we just plow through all those. I know, I said. There is only that one paper I know of that I sent to you to read. That really looks good, she said. You did a good job. I basked in the moment.

She had a whole morning to kill, so we worked on My Guy's arm together. She showed me how to shove a board under his abducted arm/shoulder and tie his wrist back to the board so we could get his skin detached up both sides right up to the axilla, all but for the little neural tunnels.

We worked for several hours, chatting away as she worked on the cephalic side of the arm and I worked on the basilar side, named for the veins, (which mean "top side" and "bottomside"). I unearthed several more layers of skin, subcutaneous fascia, a large plexus of neural tunnels on the medial side of the arm. She worked on the outside, carefully peeling away the skin/subcutaneous fascia laterally and over the deltoid. She also dissected the axilla, removing all soft tissue but for neural structures and their disseminating branches.

It was quite a sight when we were done; From the perspective of the hand end, looking medially up the anterior surface of the arm into the axilla, the deep fascia is still intact over the forearm. We have biceps loosened but not cut at its tendon, and access to musculocutaneous nerve from either side. With the big heavy thick cutaneous layers folded back, there are two huge veins visible, within those flaps, one on each side, The neural tunnels are still attached to the skin, and from the inside they run obliquely, holding the skin up like the oblique rigging on sails.

All the main zones of the arm have different thicknesses of "skin". The inner arm is thickest of all, suprisingly (to me at least); there are at least three main layers or compartments, each with their own cutaneous neural tunnels. These tunnels all sort of converge in something that looks a bit like a freeway - the nerves change from one layer to another, and continue on down, send a few branches out to the skin all the way along.

We found intercostobrachialis, the posterior cutaneous of the arm, the upper cutaneous of the arm, lower lateral cutaneous of the arm, the medial cutaneous of the arm and the medial cutaneous of the forearm. I saw what lymph nodes look like, in the axilla. She told me about her own episode of frozen shoulder. We discussed all that PT could be and wasn't.

There are more cutaneous nerves in there, completely unrelated to the ulnar and median, (many off the radial), buried right inside the skin layer(s) than I ever suspected when I started this whole project, and they come off a whole lot higher than I ever suspected- who'd have thunk? ... I've had to alter my my own understanding to concur with reality since getting the Gray's CD, and since seeing My Guy's Arm on the inside. However, reality is brilliant, and supports DNM better than my previous lack of good information/understanding.

There are many places in the pathways of the nerves where they are attached to vessels. There are many branches of nerves that go to vessels and vice versa. They never travel very far apart from each other, not in the upper arm.

The forearm is built quite differently from the upper arm. In the upper arm, there is more crossover between deep structures and the more superficial ones, the layers are less well defined even though there are more of them, and the deep fascia is less tight and thick and tough. The vessels and the nerves are in a more defined "neurovascular" bundle.

In the forearm, the deep fascia is much more defined. The median and ulnar nerves are so buried, I don't see any way to deal with them manually except through the hand. The two arm bones, interosseous membrane and musculature is very packaged, very contained. The vasculature and nerves I have looked at so far in the forearm travel subcutaneously and outside this deep stuff, although it would appear they wander away from each other a bit more than they do in the upper arm, they still plug back into each other at regular intervals.

I was told that people wanting to get into the anatomy lab are heavily screened. They admit ortho PTs fairly regularly for advanced study, but expect them to teach a class in return. My admittance probably had most to do with being the right combination of persistent and hopeful and non-expectant all at once. After all, I had a unique request. And wasn't interested in teaching, wasn't even asked. Who knows, maybe some day. But first, I'll have to get others interested. Unimaginably to me, these nice and well meaning anatomist people (I met another one there who was also an ex-physio) have never heard of Butler. It will take awhile to get this mountain moved. Meanwhile I count my blessings that they are willing to entertain a theoretical concept that is radically new to them, for which hardly any anatomy studies have been done, for which almost no actual anatomy exists, period. There's just so much mesoderm that it takes all their attention; they ordinarily just rip through all the little neural tunnels on their way to diving into and around the mesodermal stuff, preserving only the large nerves but not bothering to preserve their paths to skin. Mesodermal bias at every step of the process. Small wonder no one out in the world hardly can conceive of this neural net between layers- usually it's destroyed, not preserved/studied.

The ambition I feel toward this project knows no bounds - all I want to do with the remainder of my life now is dissect and map and document this system throughout the entire body. However, this is not likely to happen.. so my next fondest wish would be that anatomists everywhere fire up with the possibilities inherent in the exploration of this diffuse neural net, the last PNS frontier in the body, study the overall pattern of it, photograph it, draw everyone's attention toward it, toward these end organs of the kinesthetically sensing part of the brain, the organism, some of our best and phylogenetically oldest bits of nervous system.