Welcome. Today we'll go through the overview of the musculoskeletal system. We have the muscles which actually form the muscular system as well as the skeleton, and the bones and the joints which form the skeletal system. The skeletal system is going to be supported by soft tissues. The soft tissues can include ligaments, it can include muscles as we said before, and it can include other things such as tendons, cartilage…etc. The skeletal system forms the structure of the body; and our musculoskeletal system allows us to have ambulation, to help us have movements in this world. These are questions that come out from, for example, “who wants to be a millionaire” type of shows. We typically would say that the adult, a mature skeletal system would have around 206 bones. There are some variations with different people. As we said, it provides a structure for our whole body to stand up, walk and mobilize. It helps protect vital organs such as our lungs, heart and gastrointestinal tract organs, and it facilitates motion as we said before. We can split it into the skull, the vertebral column, the rib cage or the thoracic cage, the upper limb which includes the shoulder girdle, as well as the lower limb which includes the pelvis. Talking about the skeleton, we can classify or split it again into the axial skeleton and the appendicular skeleton. As the general rule, the axial skeleton, including the skull, the rib cage and the spinal or the vertebral spine helps protect the organs, the fragile things in between. The skull protects your brain, the vertebral protects your spinal cord, and the thoracic, the rib cage protects your respiratory and cardiac systems. Lower down the pelvis, does protect a little bit of your liver, spleen…etc. In the appendicular skeleton, it involves the upper limb and the shoulder girdles, as well as the lower limb and the pelvic girdle. These are the skeletons or the bones where you actually get your motion. It allows you to explore the world outside, to walk around. These joints allow us to bring things towards us and to experience the world. We can have different classifications of bones. This is mostly descriptive and we can talk about the long bones. The femur is your thigh bone and the humerus is the upper arm. And then you can have your short bones. These are the carpals, which are the ones inside your hands, and the tarsals, which are the ones inside your feet. And we get the flat bones, such as those seen in your skull and some sort of irregular ones, such as the vertebrae, which have very complex anatomy. And then some sesamoid bones, which are actually inside tendons. The patella is the most frequently talked about sesamoid. Aside from the bones, between bones and bones, there are different joints. A joint is typically supported by soft tissues including ligaments and tendons. At least two bones form a joint, sometimes three, sometimes more. Joints can be synovial joints where they are filled with synovial fluid and these joints are typically a little bit more mobile. You can think about yourself, the joints that you can move a lot more, the hip joint, the shoulder joint, these are going to be synovial joints. You have your fibrous joints, which do not really move a lot. The joints are between your different skull bones or sometimes you call them the sutures. And then we get the cartilaginous joints, such as between your vertebrae or the pubic synthesis that we would talk about especially in females. Talking about synovial joints, this is probably the first type of joint that we would think about when we talk about joints. Again, we can have descriptive motions of how they actually move. For example, the plane joint. If we look at the picture on the right, the joints between your tarsal bones, those are mostly plane joints. They can move in anterior, posterior, medial or natural types of motions. You can have your saddle joints. These saddle joints are… One example would be the first metacarpal joint in the wrist or thumb. The pivot joint, one example would be the first and second cervical vertebrae. That allows you to have that rotation of your spine and subsequently of course your skull where you can look from left to right. The ball and socket joints, again this would be, you can imagine it gives you quite a lot of mobility. The hip joint would be one example of a ball and socket joint. Hinge joints, the first thing we think of is the elbow joint. Condyloid joint, which is concave on one side and convex on the other, the wrist joint is a type of condyloid joint. These are all synovial joints and you don't have to remember these, but these are mostly descriptive with descriptive words or it just describes how these joints functions. Then you have the ligaments. To put it super simply, ligaments are the soft tissues that join bone to bone. These are fibrous bands of dense connective tissues connecting different bones. They would help stabilize different joints. For example, what we see on the right side again, the ligament that is labelled, that is the lateral collateral ligament. It stabilizes the knee joint from excessive motion. These are so-called static stabilizers of different joints, this is mostly done by the ligaments. Sometimes the ligaments would have other functions such as they act as a surface for our muscle origin or muscle attachment. And here we see the interosseous ligament between the fibula, the lateral or the outer side of the leg and the tibia bone. This interosseous ligament is the anchor site or the origin of a lot of the muscles used to control the foot and ankle regions. Again, ligaments can have different types and people would describe them descriptively again, such as so-called white ligaments and yellow ligaments. The white ones are the ones with Type 1 Collagen and the most typical or the most famous example, especially for our sports enthusiasts, would be the ACL, anterior cruciate ligament, inside the knee. Yellow ligaments, there are a little bit, mostly flexible elastic fibers and one example would be inside the vertebral column. We also have the so-called capsular ligaments, which are sometimes fused with the joint capsule. For example, the capsular ligaments in the hip joint that we have labelled on that. There are many ways to classify ligaments and one of these is the descriptive way. One interesting point worth noting is that ligaments can be intracapsular / intraarticular or extracapsular. Again, we should be touching upon this a little bit later, but intracapsular ligaments such as the anterior cruciate ligament, typically don't heal as well as the extracapsular ones, such as the medial collateral ligaments. Next is the cartilage. Inside the cartilage, we have cells and those are mostly chondrocytes. The cartilage is of course a little bit stiffer than muscle, but a little bit more flexible than the bone. What it does is, it helps the articular surfaces have a smoother motion and absorbs shock. The problem of cartilage is relatively avascular, meaning that it doesn't really have a good blood supply. Again, as a very general rule, if you don't have a blood supply then you can't really get the nutrients, all the raw material that you need for repair. So, avascular tissues such as the cartilage typically repairs quite poorly. There are different types of cartilage. Firstly, fibrocartilage. As its name implies, it's a little bit more fibrotic. It's tougher and in an inflexible form. You get the hyaline cartilage, which we see a lot in the articular surfaces and within the joint surfaces. They are strong, they have low-friction and what they do is they bear and distribute weight in our joints. hyaline cartilage is something that we basically do like, especially in the knee, etc. And then you've got your elastic cartilage. You can feel that in your ear, in your larynx and epiglottis. Those are a little bit more flexible than hyaline cartilage, maybe not so much in the musculoskeletal system though. Hyaline cartilage is the one that we really want most of the time. This is an overview. We'll quickly go on to the muscular system. “MYO” means muscles. Muscles are highly vascular. As we said before, regarding cartilages being avascular, those are relatively low vascularity. Muscles are well perfused and have a good circulation. They are typically pretty good at regeneration and repair. In terms of the different types of muscle tissues, we can split them into those being controlled by the autonomic nervous system; and those being controlled by the somatic nervous system. Regarding the autonomic nervous system, basically this is something that runs on autopilot. These muscles contract and move without your voluntary input or your conscious input. You can imagine, for example, the heart, your heart keeps beating no matter what you do. In visceral muscles, those in your gastrointestinal tract and blood vessels, these are the smooth muscles which are innervated by the autonomic nervous system. In the musculoskeletal system, a lot of motions are controlled by the somatic nervous system that you can have voluntary motions. It's the skeletal muscle that I think we are more interested in or we will focus on. As we said before, they typically do have an origin and you have that muscle belly, and then that muscle belly becomes a tendon that inserts into the bone. I'm going back when we talk about ligaments. Ligaments are the things joining bone to bone. Tendons are the things joining muscle to bone. Tendon. The structure is actually pretty similar to ligaments. We will be going into a little bit of its properties later or in different talks that follow. Tendons, as we said, are located at the end of the muscle belly. They attach to the bone and with that, you can imagine when your muscle actually contracts. The tendon transmits the force passes whichever joint they are crossing into the bone. Therefore, you can have that type of motion. In the Achilles Tendon on the right, we can see that the Achilles Tendon is actually your gastrocnemius muscle, the medial and lateral gastrocnemius, and also a deeper soleus muscle. They actually form into this Achilles Tendon which inserts in the calcaneum. This is all at the back of your calves. When you have a muscle contraction, your ankle will go into dorsiflexion, so your ankle would be moving downwards and that gives you the motion. There are some characteristics of muscle tissue. First. it's excitable. Once you get that neural stimulation, it responds to it, and it typically contracts. So the whole muscle shortens after you receive this stimulation. Again, we'll be going into a little bit more of the details in our physiology lectures. Have a little bit of extensibility and elasticity, muscles can be stretched and they can actually go back to their original length and they change, basically your whole body, all the tissues are a living thing. It can adapt to how it is used and now typically when we talk about muscles, you know when we train it up, you get that hypertrophy; when you don't train, you get that atrophy or wasting of the muscles. Just to recap. Muscles have two main functions. It allows mobility through your muscle attachment into transmitting the force via the tendons and you create motion in different joints. It also gives you some sort of stability. We always talk about the core muscles stabilizing your trunk. Actually, the muscles give your joint stability too. So now, it's a little bit more complex, but sometimes when we talk about, for example, patients with knee pain. Training up the muscles surrounding the knee can actually improve the joint stability and decrease different types of symptoms, e.g. pain in some of your patients. The muscular system is important for circulation. As said, for the heart and for respiration, including controlling the rib cage. It does have some roles in thermal regulation. It can regulate your body temperature, and digestion, and protect different organs. Here are some major muscle groups in the body. In the front, we have your pectoralis, and you have your abdominal muscles. In the lower limb, you have your quadriceps over the front, which are the main knee extensors. In the shoulders, you have your deltoid, which gives you that abduction of your shoulder. In the back, all the trapezius, latissimus dorsi, gluteus muscles, hamstrings…etc. Knowing the anatomy of muscles is important. Knowing where they originate from and where they insert are important. Because as soon as you know that, you can figure a lot of things out just by knowing the anatomy. You know how this muscle would move. Sometimes even for, let's say, gym goers, they would know how certain exercises or certain motions, what type of muscles they would be training and moving. There are different contractions. Isometric contraction of a muscle means that your muscle is contracting or is being stimulated, but the muscle length does not change. The easiest example of this would be, e.g. if you are pushing against an immovable object. Let's say you are pushing against the wall. That would be a type of isometric contraction. Let's say, on the right side, if you were holding a dumbbell with your elbow, you can see this is your elbow slightly at 90 degrees. When you are holding that and you're not moving, so even if you're just holding it in place in a static position, your muscles do have an isometric contraction. Otherwise, you're just giving away. I'm using this bicep curl as an example. It's often easier to think about concentric contraction and eccentric contraction of the muscles. Concentric is quite easy. Let's say you are holding your dumbbell, you have concentric contraction of your biceps. What happens is your bicep shortens and you can actually flex and do your bicep curl. The eccentric contraction is the thing that comes after. When you have that type of slow controlled putting or slow controlled extension of your elbow while holding that dumbbell in your biceps. That is when you have the eccentric contraction of your muscle. Concentric contraction is when you're flexing, and then you do your bicep curl. Eccentric contraction is when you are slowly, in a controlled manner, extending the elbow. A lot of people actually get this wrong. They would think that extending the elbow means it's actually the function of your triceps. It's not that simple. Because if you do that, then you don't really or you can't really control the sort of extension of your elbow. You can just feel it. If you are at home or you are in a place where you can actually feel your biceps, just try to do that concentric contraction, to feel when you do that slow, control extension of your elbow, feel your biceps. It is still contracting, it's still not relaxed. It is an eccentric contraction. There are different fibers again. We may go into a little bit more detail later. Most people know that there are the so-called slow twitch and fast twitch fibers. The “RED” ones basically mean that it has a lot of aerobic metabolisms. These are the ones that are relatively fatigue resistant. These are the fibers or the muscle fibers that you use or you train in endurance events. You have your fast twitch fibers, which are really more for your explosive power. These are anaerobic, so these work by anaerobic metabolism and they are easily fatigued. Different individuals who have different ratios of these so-called “RED” and “WHITE” fibers. I think the detail is a little bit out of the scope of today's talk. We do want to talk about the different joint motions. You can see that we're just going to be playing all these videos. The one we're doing right now is extension and flexion of the elbow. Then you have your abduction, which is away from your trunk and abduction of your shoulder on the right-hand side. And you have rotation, you can have an external rotation of your shoulder. The internal rotation of your shoulder. This would apply for all joints. This is how you describe the different types of motions. When we have a loss of muscle mass, it can be due to various causes, disuse or atrophy. I mean atrophy is one when you have inactivity and then you lose nervous supply. You lose these motor neurons and then your muscle becomes wasted with time. Sometimes you can have dystrophy which we would say it's more congenital or genetic related. You can have some inherited diseases which gives you muscular dystrophy. Another term that I guess most of you would hear a lot is sarcopenia. This means that the muscle mass is a little bit lower and this typically happens in more senior individuals where you actually lose muscle mass and a lot of it is just going to be replaced by fatty tissues. Alright, so this is a quick overview of the musculoskeletal system. Don't worry too much because we will be going into a little bit more detail on some of these topics later in the different t