The three main types of muscle
Muscles produce the force required for movement within the body. A muscle cannot move by itself – it needs to interact with the skeleton to provide movement. The nervous system (brain, spinal cord and nerves) coordinates the muscular contractions allowing movement to occur.
Muscles comprise approximately 45% of total body weight, and there are in excess of 600 muscles in the human body. These are comprised of three types of muscle tissue:
- Cardiac muscle (myocardium): this is found only in the walls of the heart and is used to force blood into the circulatory vessels. There is no voluntary control of contraction of the heart. The muscle cells are all connected allowing them all to contract in an organised sequence.
- Smooth muscle: this lies internally and has several functions including forcing food through the digestive system (peristalsis) and squeezing blood throughout the circulatory system via arteries and arterioles.
- Skeletal muscle: these are external and are used primarily for movement around a joint, but can also be used to hold a body part in a stable position. These often occur in layers, with ‘deep’ muscles which lie beneath ‘superficial’ muscles. They are usually attached to bone, or in some cases to other muscles (e.g. the abdominals). Skeletal muscle is under voluntary/conscious control (unlike smooth and cardiac muscle).