Working in unison, the joints, bones and skeletal muscles of the body comprise your musculoskeletal system. The primary function of these components working together is to create movement. Other functions include stability, posture and protection. Along with the joints, which act as fulcrums, the bones and muscles work together to create levers in the body. Depending on the location of the load in relation to the joint or fulcrum, muscles and bones create either a mechanical advantage or disadvantage when you lift an object. The closer the load to the joint and the farther away the muscle, the easier it is to lift the object. Conversely, the farther the load from the fulcrum and the closer the effort to the fulcrum, the more difficult it is to move the object. Show Where They Come TogetherThe point of articulation, or where the muscles and the bones connect, is known as a joint. Tendons are a form of connective tissue that is continuous with muscle fiber and actually connects muscle to bone. Skeletal muscles that produce movement are attached to two bones that articulate, or meet. When movement occurs at any given joint, only one of the articulating bones will move. The stationary bone is known as the point of origin for the skeletal muscle. The bone that moves is considered the point of insertion for the muscle. Video of the Day How You MoveWhen a neurotransmitter or message is sent for movement to occur, your body releases energy, in the form of adenosine triphosphate. ATP causes the contraction or shortening of skeletal muscle. When the specified muscle shortens, it pulls on the corresponding bone at its insertion point. This contraction shortens the distance of the angle between the articulating bones, with the joint acting as the fulcrum. Upon receiving the signal to relax, the muscle opposing the contracted muscle will then act to extend the movable bone back to its original position. Bones, muscles and joints make up the musculoskeletal system, along with cartilage, tendons, ligaments and connective tissue. This system gives your body its structure and support and lets you move around. The parts of the musculoskeletal system grow and change throughout life. Injuries and various illnesses can damage bones, muscles and joints. Parts of the musculoskeletal system
What do bones do?Bones give people shape. They hold the body upright, and also protect organs like the heart and the liver. They store the minerals calcium and phosphorus, and also contain bone marrow, where new blood cells are made. Much of the skeleton is made up of non-living material (including the minerals calcium and phosphorus), but nevertheless bones contain living tissue which is constantly remodelling, replacing old tissue with new tissue. The centre of bones contains the bone marrow. This produces new blood cells. The spine or vertebral column is the central support of your body, helping it walk, move and twist. It has 33 bones called vertebrae, separated by discs. The spinal cord runs down the centre of the spine, carrying all the nerve signals from the brain to the rest of the body and also carrying sensory input from the body back to the brain. The What do muscles do?There are different types of muscles, each with different functions, but they all work to produce movement of the body or to stabilise the body. Skeletal muscles are also responsible for generating heat in the body to maintain body temperature and help regulate blood sugar levels. Skeletal muscleSkeletal muscle (voluntary muscle or striated muscle) is muscle that you can consciously control. Skeletal muscles run from one bone to another, usually passing at least one joint. Each muscle is comprised of muscle tissue, blood vessels, nerves and tendons. Skeletal muscles are usually attached to the bone by tendons. When your brain tells a muscle to contract, it shortens, pulling one bone towards another across a joint. Muscles work in pairs — when one shortens, a corresponding muscle lengthens. For example, when you contract your bicep on the front of your upper arm, your tricep on the back of your upper arm lengthens. Physical activity maintains or increases the strength of skeletal muscles. Skeletal muscle plays an important part in regulating blood sugar (glucose) levels, by taking up glucose from the blood to use as fuel or to store for later. Smooth muscleSmooth muscle is found inside blood vessels and organs like the intestines. You can’t consciously control smooth muscle. It contracts to move substances through the organ, and so helps regulate your blood pressure, airways and digestion. Cardiac muscleThe heart is made of special muscle called cardiac muscle. You can’t control it consciously. It contracts to make your heart beat under the control of the heart’s inbuilt pacemaker — the sinoatrial node. What do joints do?Joints connect bones. They provide stability to the skeleton, and allow movement. There are different types of joints. Synovial jointsJoints in the arms and legs are synovial joints. The ends of the bones are covered with cartilage and separated by the joint cavity which is filled with a thick gel called synovial fluid. Synovial fluid helps to lubricate the cartilage and provides nourishment to it. Ligaments stretch across the joint, connecting one bone to another and help to stabilise the joint so it can only move in certain directions. Cartilaginous jointsJoints in the spine and pelvis and the joints between the ribs and the sternum are cartilaginous joints — they provide more stability but not as much movement. The bones are connected by cartilage in this type of joint. Fibrous jointsFibrous joints allow no movement — just stability. They are held together by fibrous connective tissue. You have fibrous joints in your skull. Conditions and injuries affecting the bonesMany different conditions and injuries can affect the bones, such as:
They all have different forms of treatment. The best way to have healthy bones and prevent illness and injury to the bones is to eat a healthy diet that includes calcium-rich foods, limit soft drinks, caffeinated drinks and alcohol, be as active as you can, do weight bearing and high impact activities if you can, get enough sunshine and keep to a healthy weight. Disorders affecting the jointsMany conditions can affect the joints. Arthritis, which is characterised by joint pain and stiffness, is one of the most common. Different types of arthritis have different causes. Some conditions that can affect the joints are:
Disorders affecting the musclesMuscle injuries and disorders can cause weakness, pain or paralysis. Sports injuries are a common way that muscles can be damaged. Conditions affecting the muscles include:
Who can help?If you are having problems with any part of your musculoskeletal system, your doctor (GP) is a good place to start. Other healthcare professionals who are involved in diagnosing and treating musculoskeletal problems are physiotherapists and specialists such as rheumatologists or sports medicine physicians. |