Your body’s muscle tissue is made up of specialised cells with greater stretchiness, or ‘contractility’ than regular cells. Muscle has the primary purpose of flexing and contracting, and even though all cells in your body have the ability to contract slightly, muscle tissue can do this to a far greater extent. You have 650 muscles in your body, accounting for about half of your body weight. There are three main types of muscle in your body: smooth, cardiac and skeletal.
The simplest type of muscle, these are the type you have in your internal organs, including the respiratory system, the digestive tracts, and the blood vessels. Smooth fibres in the skin also help to regulate heat loss in the body. They also line your body’s various ducts and tubes, such as the reproductive tubes, and help to push their content along to their destinations. They are usually arranged in sheets or layers, and generally contract automatically.
Like smooth fibres, cardiac fibres also contract automatically. They are found only around the heart, and have developed the specialised purpose of keeping the heart pumping rhythmically. They start working very early in an embryo’s development.
Also known as striated, somatic and voluntary, its function is to produce movement, maintain posture, stabilise joints and generate heat. These muscles cover your skeleton and give your body its shape. Unlike the smooth and cardiac variety, skeletal muscles are controlled by your conscious mind, rather than the autonomic nervous system. These fibres contracting generate all body movement, and they are functioning almost continuously to keep your body upright and maintain your posture. They also hold your bones in the correct position and stop your joints from dislocating. The heat generated as a side effect of their continuous work maintains your body temperature.