Your muscles make up about half of your body weight and can be divided into three separate groups… skeletal, cardiac and smooth. These groups can all stretch and contract, but each play very different roles.
Skeletal muscles are voluntary muscles positioned between two bones and cause movement of one of these bones by contracting or shortening. The other bone will be stabilised by its very nature such as the rib cage or sternum or by another muscle such as the Deltoid stabilising the humerus.
Skeletal muscles cover your skeleton, and give your body shape. They are attached to your skeleton by strong, flexible tendons or are directly connected to rough patches of bone. Skeletal muscles are subject to voluntary control, which means you consciously and deliberately control their actions.
Every move you make, from walking around to scratching your nose, is caused by skeletal muscle contraction. Your skeletal muscles function almost continuously to maintain your posture. Always on the job, they are constantly making small adjustments to keep your body upright.
Skeletal muscles are also crucial for holding your bones in the right position and prevents your joints from dislocating. If we didn’t have skeletal muscles, we’d be in an untidy heap on the floor.
Some skeletal muscles in your face are attached to your skin. The slightest contraction of one of these muscles changes your facial expression and it takes more muscles to frown than it does to smile. We still see them though… people doing it tough and working hard… at frowning!
Skeletal muscles produce heat as a consequence of muscle activity. This heat is essential for maintaining your normal body temperature.
Your heart is made of cardiac muscle. This type of muscle only exists in your heart. Other types of muscle get tired, but not this one. The cardiac muscle never gets tired. It works automatically and 24-7, without rest. Cardiac muscle contracts to squeeze blood out of your heart, and relaxes to fill your heart with blood only to squeeze it out again.
Found in the walls of hollow organs like your stomach and intestines, they work without you being aware of them. The muscular walls of your intestines contract to push food through your body. Muscles in your bladder wall contract to expel urine from your body. Smooth muscles in a woman’s womb help to push babies out of the body during childbirth. The pupillary sphincter muscle in your eye is a smooth muscle that shrinks the size of your pupil.