• scissors
    February 12th, 2011ImogenUncategorized

    This Study of Arms by Leonardo da Vinci shows the muscles in wonderful detail. You can see how far up the arm the tendons for the fingers go.

    I recently had the pleasure of going with my Dad to see Richard Thompson and band performing at the Royal Festival Hall. The concert was amazing, and from our meticulously booked seats I had a great view of RT’s playing. I was fascinated by the muscles apparent in his right forearm as he plucked and strummed. My dad tells me that Mr Thompson practices for two hours a day (even on tour!) and although his arms are not “hench” (as some of my friends back home may say) and hugely bulky, the muscles for his fingers are certainly well-honed.   As you can see in Leonardo da Vinci’s sketch, there are very few muscles actually in the hand. Fingers are controlled by muscles in the arm and the two are connected by tendons.

    Muscles make us move, but like everything else in the body they can go wrong. What I would like to know today is: what are muscle knots? After looking into the answer I find that it is actually relatively simple, they are parts of a muscle that have contracted, but not relaxed along with the rest of the muscle. Muscles can only pull (never push) so a muscle is either contracted or relaxed. A muscle fibre is made up of lots of filaments that slide over each other to create a pulling force. As the filaments overlap more the muscle becomes shorter and more compact. You can see this in action by looking at your inner forearm as you make a fist. Place another hand on your forearm as you do so and you will feel the active muscle changing shape as it contracts. When I do it my hand is also involuntarily lifted up slightly as the muscle shortens.

    So apparently, these knots are actually known as myofascial trigger points. The most common way to remove them is with massage or using hot or cold packs which will encourage the muscle to relax. You can also use electrostimulation or pulsed ultrasound (woo ultrasound!). I actually had electrostimulation while I was seeing a physiotherapist to correct my spinal scoliosis. I can inform you that it is very relaxing and feels like pins and needles.

    I can’t find much information on why these “trigger points” are painful but I make the educated guess that the pain is due to lactic acid build up as the muscle respires faster than the blood can deliver oxygen to it. This is the same source of pain as when you work a muscle very hard, for instance, when running up stairs. From my own experience, massaging a muscle knot is painful too. Does anyone know why this is?

     

    If you’d like to know more about how a muscle contractions then here is a great animation I heard about from my physiology course. Even if you’re not interested in all the fancy names (let’s face it, you’re not going to want to learn them all if you don’t have an exam on it) you might find it interesting to see how the components move past each other.

    Happy muscling!

    Tags: ,
  • scissors
    February 8th, 2011ImogenUncategorized

    In My Humble Opinion, Ultrasound is very cool. It is not as amazing to look at as MRI, nor as potentially lethal as X-Rays, but it can be used for a lot of diagnostic purposes. Many of us may remember ultrasound imaging from that grainy black and white image someone showed you excitedly as you tried to work out what it was. Or if you are like me and have not had any pregnant friends, remember that scene in Friends? This is because pregnant women on the NHS are currently offered at least 2 sonograms during their pregnancy in order to calculate the age of the foetus and to check it is growing healthily. Therefore this is the way in which we are most aware the way of using high-frequency sound to image inside the body.

    However, the applications are much broader. The first ultrasound machines were basically modified flaw detectors. Flaw detectors were used by ship builders to detect faults in the metal hulls of boats. The sound waves travel through the metal and are reflected by the air which fills cracks and imperfections. The connection was made by Ian Donald, Regius Professor of Midwifery at the University of Glasgow (Regius means that the post was originally created by a monarch and each appointment must be approved by the crown. This position was founded in 1815 by King George III). He was a keen sailor and became familiar with Sonar and Radar while serving in the RAF in the Second World War. Sonar was developed after the sinking if the Titanic and used sound waves to probe several miles of ocean. Any reflected sound indicated the presence of a possible ship-sinking object. Radar works in a similar way but using radio waves. It was Douglas who first brought ultrasound into the hospital to peek at babies in utero. Many developments then followed to develop the machines we use today, which have a mobile computing and display unit and a small probe on a flexible arm. The first machines required the examinee to sit in water bath so that the probe could achieve a good contact. This is because however hard you press a plain old probe against the skin; some air will still exist where the two meet. The air will reflect the ultrasound waves before they even get into the patient so that you will just get a useless fuzzy image. The modern ultrasound gel is water based (easier to remove than oil-based formulations) and forms a perfect air-free join for the sound waves to pass through before and after the body. It’s true what everyone says though, it does feel very cold when they put it on.

    Unlike X-rays, ultrasound does not fall under the classification of “Ionising Radiation”. That means that when the waves pass through your body they will not cause damage and so their use as a diagnostic tool does not need to be restricted in the same way. In light of this, ultrasound is frequently used to view active functions inside the body, in particular the function of the heart. A physician may employ ultrasound to view the action of particular heart valves if he suspects that the heart is not pumping correctly. By examining arteries to the brain and lower body it is possible to assess the risk of getting a stroke or blood clot by looking for plaque in these important vessels. During the first three months of a foetus’s life, the cells are dividing more rapidly than at any other point in its existence. More cell divisions mean more opportunities for things to go wrong, so to X-ray a baby at this point would be very hazardous. Therefore, non-ionising radiation such as Ultrasound is invaluable to check up on the baby without harming it. Recently, scientists have developed a pre-natal test for Down Syndrome which does not require an extraction of cells from the uterus. This is good because tests such as amniocentesis or chronic villus sampling (both of which use a needle to take cells from the amniotic fluid or placenta respectively) carry a risk of miscarriage. In the new technique, a ultrasonographer examines the nasal bone since babies with Down Syndrome tend to have a flatter bridge of the nose and almost nonexistent nasal bone. A test for “nuchal translucency” can also estimate the thickness of the skin at the back of the neck using a high-frequency ultrasound. A higher than normal thickness can indicate a genetic abnormality.

    However, ultrasound can be used for quite different purposes. Some anti-abortion politicians in certain states in America (such as Montana) think that women seeking a termination should have to have an ultrasound scan and listen to the foetus’s heartbeat for up to one hour before making a final decision. Abortion is a highly controversial issue and if this scan was compulsory then it would not fail to emotionally affect both the woman faced with this decision and the doctor forced by law to carry out the procedure. Some very interesting moral questions are raised, but this is not a political blog, so I won’t say more on the matter.

    AND SO to haul this post back from grim opinion-ism , I would like to draw your attention to this lovely little story I read the other day about the amusing pictures ultrasound can capture. Aaaaaah.

    Tags: ,