Week 114: anatomy of the bladder

The renal systemThis week we pretty much finished off looking at the renal system by looking at the bladder (we only have the male urethra yet to study).
We used visiblebody.com to get an idea of where the bladder is (and that it is anterior within the pelvis, right up against the pubis bones) and the shape of the bladder. Textbooks sometimes describe the bladder as an upside-down pyramid, which kind of fits. Visiblebody.com shows the shape quite well, which is something that’s difficult to get from an image or a prosection. Some of the plastic models in the lab are quite good, and most of the torsos have them.
Remembering that the bladder is the most anterior viscera in the pelvis is helpful. When looking at prosections, particularly of female pelvises, it can get a little confusing. Remembering that the bladder is anterior makes it easy to locate and identify (male: bladder-rectum, female: bladder-vagina-rectum).
The bladder receives urine from the two ureters that enter its posterior wall (also known as the base). The ureters don’t have real sphincters to prevent backflow from the bladder, but they do pass through the detrusor muscle of the bladder at an angle that gives a physiological sphincter.
The bladder is lined with a specialised epithelium called transistional epithelium or urothelium that allows for the stretch of the bladder as it fills and is not too fussed about constantly being in contact with urine. This urothelium lines a layer of detrusor muscle that contracts to squeeze and empty the bladder (so, along with the peristaltic contractions of the ureters this means that you should be able to urinate upside-down, or in space – this isn’t a gravity-fed system). When the detrusor muscle contracts it also squeezes and closes off the ureters.
Internal bladderThe trigone of the bladder describes a triangular area of the bladder seen as a smooth patch internally, between the ureters and the urethra. Here the urothelium is tightly adherent to the detrusor muscle. Elsewhere the inside of the bladder appears folded, much like the rugae that we saw in the stomach.
The urothelium and the rugae allow the bladder to stretch to hold maybe 500ml of urine or more. By this point your parasympathetic nervous system may well have triggered the detrusor muscle to squeeze and the internal sphincter muscle to open to try to empty the bladder. Luckily you still have control over the external sphincter (and your levator ani muscle group) so hopefully you can hold on until you find somewhere appropriate to relieve yourself. Before your bladder fills to maximum capacity your micturition control centre in your frontal lobe will hopefully give you a level of control over where and when you choose to empty your bladder (and you can read more about nervous control in this eMedicine article: Neurogenic bladder.
The neck of the bladder is its most fixed part, and we saw in the prosections how mobile the bladder is. It is supported and surrounded by the muscles of the pelvic floor, the obturator internus muscles, the visera of the pelvis, the peritoneum, and the overlying small bowel. In the female pelvis the neck of the bladder is attached to the pubis bones by the pubovesical ligament, and in the male pelvis by the puboprostatic ligament (and as the name implies, the prostate gland directly inferior to the bladder is also fixed in place by this).
You may wish to review the blood supply of the pelvis as a whole (particularly the branches of the anterior trunk of the internal iliac artery) to better understand the arteries that supply the bladder in both male and female pelvises but I won’t go into that here. Maybe take a look at this diagram on Instant Anatomy.

How much energy can you produce on your bike?

For 12 hours?
The BBC’s Bang Goes the Theory programme investigated (and demonstrated) what it would be like to try to power a single household by pedal power. Sure, it’s not a practical idea but it gives the viewer some real energy awareness. Well, if the viewer has ever ridden a bike anyway.
I won’t be powering the microwave when I’m on the turbo then.
See the whole thing on iPlayer if you’re in the UK (probably until the 10th December) here.

From one period to the next

2009-12-06--December SunI’m coming to the end of my transition or recovery period after this year’s racing, and after the Dublin marathon in particular. I’ve been taking it really easy for 6 weeks, training as I feel like it and eating wheelbarrow loads of doughnuts and cakes. I’ve done very little running, had a full week of swimming, done a bit of biking, and completed some off season testing. I played a little golf, but not as much as I would have liked. The weather has been horrible (so a good time to not be training). I’ve been planning next year’s racing and training, and getting some kit together. I’m associated with a team swim across the English Channel too, so I’ve been trying to plug that into the year’s programme too. (If I end up swimming I should be in great condition by September, but I might be a bit too skinny for the cold water…)
I’ve hit the point where I’m really looking forward to getting back into a structured training regime. That suggests that this break has been good for me mentally as well as physically. I pretty much destroyed my legs in training this year and was glad of the break. I won’t be training much, but I’m actually looking forward to early nights and early mornings (I’m not sure Kim is though). I’ll be doing far less running, but will probably be hitting a similar weekly mileage to that of this time last year. I’m not sure how well I’ll fit the biking in, but it’ll be good to get in three or more swims a week with some coaching and see how much I can improve. The biking just feels like playing at the moment.
After four weeks of this I’ll begin to increase the volume, and I’ll really start training towards a season of triathlon. I completed my last triathlon 6 years ago!

A year in preparation

I mentioned in my Dublin marathon race report that I’d show some data from the year of training leading up to that race. What do you have to do to run a 2:46 marathon?
Let’s start with the year before I started preparing, i.e. from November 2007 to October 2008. Here’s a graph of all the running I did during that period (the blue bars are km of running per week):
Running And Weight, 24-12 Months Before Dublin
You can see that I started running regularly in September 2008. Before that I was playing a fair bit of golf, cycling to work and running occasionally for fitness’ sake. I logged 403km of running for the whole year, and most of that was done in September and October.
Look at all my training for that same period:
Time, Cumulative 2-1 Year Before Dublin
This is a graph accumulating time so hours for each week are added to the grey columns, and I was averaging 3 and a half hours a week of mostly cycling to work with the odd run. I logged a total of 171 hours for that 12 month period, and the increasing steepness of the “curve” towards the end of the year reflects that start to my run training. The gap in December 2007 and part of January occurred just after Annabel was born. She was in the neonatal unit from her birth until Christmas and I spent that entire period with her, Kim and Jack and doing what they needed. I didn’t cycle to work as I was ferrying Kim and Jack around by car, and the neonatal unit is at the hospital by the university. You can also see a drop in sleep hours (green line) between the start and end of that period, but I doubt I recorded much data during that period at all. I was on coffee and Red Bull to try and maintain brain function.
Let’s compare those data with the 12 months leading up to the marathon then:
Running And Weight, 12 Months Before Dublin
That’s quite a nice, organised chart. You can see the increasing volume with each week (blue bars are km run per week), with recovery periods every 4 weeks and a few easy weeks in places for mental and physical recovery. I went from running the occasional 5km in 2008 to a big week of 122km, which was actually a total of 143km in 7 days from Sunday to Saturday (I raced a half-marathon in Pembrokeshire on the Sunday and then ran 122km over the next 6 days). I logged 3294km over that 12 month period. The marathon week is at the far right of the chart, and you can see the taper weeks leading to it.
That’s a huge and potentially dangerous increase in running volume, and I was only able to do it with the help of Gareth Davies at the Swansea University Sports Village who looked after my legs. As a sports therapist he picked out my weaknesses and gave me strength training programmes to fix them, and massage to help me repair. With time the long runs got easier and became normal runs, and the long runs got longer. When I started running it was with the thought of running a sub-3 hour marathon, but I still remember finding 7-minute/mile pace really tough and thinking, “26.2 miles of that?!”
I had never competed at half marathon distance before. I don’t think I’d ever run more than 7 miles before.
So I’ve suggested that I was doing more than just running. Let’s look at my training hours for everything (running, cycling, swimming and strength work):
Time, Cumulative 1 Year Before Dublin
Compared to the previous year that’s a monster chart. It’s another cumulative chart adding hours onto hours. I logged 656 hours of training and averaged 12 hours a week. As I got used to the volume 12 hours became a damned easy week. I’m still training for around 10 hours a week now in the off season when I’m just doing what I feel like. Clearly, early in the season I was still getting used to training and running again, and as the volume increased I began to average 15 hour weeks later in the season. The blue line is a measure of exertion (taken from heart rate data) and the peaks indicate races or particularly hard training sessions. If you look closely at each week block you can often see a small peak mid-week (tempo run) and a taller peak at the end of the week (long run). The biggest peak of them all at the end of the chart is the marathon.
There’s a big difference between the 2 12-month periods. I think I’m probably on for a 650-hour year for this calendar year, and with the swap towards cycling I’ll probably have a 700-hour year next year. That’s about as much as I can fit in at the moment (with some serious time management).
So what does it take to run a 2:46 marathon? Well, it took me around 650 hours of training, with almost 3300km (2063miles) of running, 2 hours a week in the gym, 5 hours a week on the bike and a couple of swims a week for a year. Volume did wonderful things to my legs but without the other work to strengthen my legs and core I wouldn’t have managed it.
There are far too many important factors in all of this to list, but being aware of my fatigue and recovery was crucial to me this year. Also, following training plans from the Runner’s World Smart Coach pushed me and showed me that I was capable of more than I would have expected. Reading as much as I could also helped me understand what I was doing. Joe Friel and Peak Performance have always been awesome sources of information. Inevitably however, much of training and racing is finding out what works best for you. And that’s part of the fun.

Google Wave, aha, I get it

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There’s been a lot of chatter about Google’s new product, “Wave“, for the last couple of months. Looking from the outside it’s difficult to see what it does, what it does different, and what we can really use it for. It’s in beta at the moment so only a limited number of people are able to actually use it.
I was kindly given an invitation to try it and as soon as I got into the preview it was clear how hugely beneficial this could be to people like me with organisational nightmares. To teach anatomy we have 2 main lecturers, 3 technicians and dozens of clinical teachers. We need to co-ordinate the teaching of 450 learning outcomes, a shed-load of exam questions, and the use of a varying number of prosections, models, bones, projectors, laptops, and rooms among a different group of people every week. Try doing that through email. Luckily Jo’s brain can cope with much of this but we still make mistakes.
So imagine something that’s easy to access that looks like email. Except that we can all edit, add to and delete our plans live (we can all edit the same stuff at once, and see those edits in real-time) and talk about it while we do it. This is all well organised in itself and we share these waves among those that need the information and keep the others to ourselves.
I can see who will be teaching which learning outcomes, have a discussion about how to link my bits in with other people’s bits, lob up images for the other teachers to use, and Greg (our technician) can suggest the materials we have available and we can all argue about who gets to use the plastic model of the arm with the nerves on it and who gets to use the prosections. Good stuff, eh? I can argue with a surgeon that he’s better suited to teaching part of the abdomen, and I can amend his assigned learning outcomes and he can suggest additions and take away stuff that’s not important. The history of this development is all recorded – nothing is lost and we can all see who did what.
The discussions we need are far more likely to take place in this environment than face-to-face. We’re all too busy and most of the people involved need 6 weeks notice to get help with clinics if they’re going to spend a morning with us. Try getting 4 or 5 of those people in a room together. It’s not easy.
The key here is that it’s very easy to use. People are scared of wiki’s but they won’t be scared of this. The whole School of Medicine could take advantage of this.
Take a look at this long preview video and see if it makes sense for you. You can use Wave with me using samvwebster@googlewave.com.

Week 110 – anatomy of the elbow (well, movements & muscles)

On Monday I spent most of the morning flexing my guns and poking my cubital fossa. Our aims were to look at the movements of the elbow joint, the muscles involved, and the important structures passing through this region, with particular regard to the cubital fossa. That video makes me feel a little bit ill. And I’m an anatomist.
We talked about the major movements of flexion and extension of the elbow joint, which you all were aware of, and mentioned pronation and supination of the forearm. I didn’t talk about the bones or the articulating surfaces in much detail as my clinical colleagues had pinched all the skeletons, and I’m sure they did a far better job of talking about the osteology than I would have done. Focusing on flexion and extension we identified the three main muscles involved: biceps brachii, brachialis and triceps brachii.
The biceps brachii muscle has 2 heads. The short head arises from the coracoid process of the scapula and the long head arises from the supraglenoid tubercle (lumpy bit above the glenoid cavity of the shoulder joint). The long head must pass through the shoulder joint, change direction and then run through the bicipital groove (or intertubercular sulcus) in the humerus. Have a brief look at the humerus and scapula in the anatomy lab to be clear on where these bony bits are.
The fibres of the biceps brachii muscle come together distally to insert into the radial tuberosity (another lumpy bit, on the radius). This means that not only is the biceps muscle a flexor of the elbow joint, but it can also powerfully supinate the forearm when the elbow joint is already flexed. Try this out next time you’re turning a screw or a bolt – feel biceps contract as you supinate the forearm and tighten the bolt. This also explains the different biceps flexing poses that bodybuilders may use to show off biceps (i.e. it’s bigger when the forearm is supine – get posing in front of the mirror to check this).
Bicipital aponeurosisThe other thing we talked about with regards to biceps was that you can palpate not only the tendon inserting into the radius but also a weird, flat tendon medially. This is the bicipital aponeurosis (see me poking mine in the photo to the right), and connects the biceps to the deep fascia of the forearm. Clever, eh?
Don’t forget that as biceps brachii also crosses the shoulder joint it is also able to flex the glenohumeral (shoulder) joint, although it’s not great at this.
Deep to biceps we found the brachialis muscle arising from the humerus and passing across the elbow joint to insert into the tuberosity of the ulna. This muscle is flattened, and is the most powerful flexor of the elbow joint. The musculocutaneous nerve runs between brachialis and biceps brachii, innervating both muscles.
To extend the elbow joint we use one muscle: triceps brachii. By it’s name this must be a muscle of the brachium (upper arm) with 3 heads. The long head comes from the infraglenoid tubercle on the scapula (on the other side to the long head of biceps brachii), the medial head comes from the posterior surface of the humerus and the lateral head also comes from the posterior surface of the humerus, but a little more laterally. There’s a groove between the medial and lateral heads, and in this groove we find the radial nerve. This is the nerve of the posterior compartment of the arm and it is innervating the triceps muscle.
All of the muscle fibres of triceps come together to insert in the bony, sticky outy bit of the elbow (very sticky outy in my case, as some of you noticed): the olecranon. The olecranon is part of the ulna, so contraction of the triceps muscle pulls the olecranon and extends the elbow.
2009-09-11--BrachioradialisThe next bit to look at was the cubital fossa. We had to find the brachioradialis and pronator teres muscles to find the lateral and medial borders, and add an imaginary line between the epicondyles of the humerus to add the proximal boundary. Brachioradialis is pretty easy to find on the lateral edge of the anterior supinated forearm, running from the humerus to the radius as the name implies. It is also innervated by the radial nerve, and when we lifted the brachioradialis muscle at the border of the cubital fossa we found the radial nerve twisting around the humerus to get to the anterior side.
Pronator teres was a little trickier to find, but it was clearly running diagonally across the proximal part of the forearm. Structures within the cubital fossa looked as though they would be protected by the biciptial aponeurosis.
What did we find in there? We saw the median nerve running (medially) alongside the brachial artery within the fossa itself (i.e. superficially to brachialis but deep to the fascia and skin) and noted that the median cubital vein, from which blood is commonly taken, was a superficial structure here. You remembered, of course, that this was where you listened to the brachial pulse when taking someones’s blood pressure.
After chatting about funny bones, we realised that we could now find all the major neurovascular structures of the upper limb at the elbow. The ulnar nerve is where we bang it (that made more sense during the discussion), the radial nerve is deep to brachioradialis, the median nerve is on the medial side of the cubital fossa with the brachial artery, and the musculocutaneous nerve peters out from between the biceps brachii and brachialis muscles as a cutaneous nerve, having done it’s “musculo” job.
Not bad for 25 minutes work.
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