Our Musculoskeletal System
The musculoskeletal system provides the framework for the body and allows the body to move. It also protects and gives the body shape.
Bones are hard, rigid structures that are made up of living cells. Long bones (leg bones) bear the weight of the body. Short bones allow skill and ease in movement. Bones in the wrists, fingers, ankles, and toes are short bones. Flat bones protect the organs. Such bones include the ribs, skull, pelvic bones, and shoulder blades. Irregular bones are the vertebrae in the spinal column. They allow various degrees of movement and flexibility.
Joints are the points at which two or more bones meet. Joints allow movement. There are three types of joints:
1. Ball-and-socket joint – allows movement in all directions. The joints of the hips and shoulders are ball-and-socket joints.
2. Hinge-joint – allows movement in one direction. The elbow and knee are hinge joints.
3. Pivot-joint- allows turning from side to side. The skull is connected to the spine by a pivot joint.
Muscles – there are more than 500 muscles in the human body. Voluntary muscles can be conciously controlled. Muscles that are attached to bones (skeletal muscles) are voluntary. Arm muscles do not work unless you move your arm; likewise for leg muscles. Involuntary muscles work automatically and cannot be consciously controlled. Involuntary muscles control the action of the stomach, intestines, blood vessels, and other body organs. Cardiac muscle is in the heart. It is an involuntary muscle.
Muscles perform three important body functions:
a. movement of body parts
b. maintenance of posture
c. production of body heat
Some muscles constantly contract to maintain the body’s posture. When muscles contract, they burn food for energy, resulting in the production of heat. The greater the muscular activity, the greater the amount of heat produced in the body. Shivering is a way the body produces heat when exposed to cold. The shivering sensation is from rapid, general muscle contractions.