The skeletal system
The skeletal system includes bones1, joints, cartilages and ligaments. The joints give the body flexibility and enable movement. However, from a structural point of view, the human skeleton system consists of two main types of supportive connective tissue: bone and cartilage.
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Are there more bones or more muscles in a humanbody?
The main functions of the skeletal system are:
- support, because it forms the internal framework that supports and anchors all soft organs;
- protection, bones protect soft body organs;
- movement, because skeletal muscles attached to the skeletal system use bones to move the body and its parts;
- storage, fats and minerals like calcium and phosphorus are stored in the internal cavities of the bones;
- blood and cell formation, which takes piace in the marrow cavities of certain bones.
No matter what their shape is - long, short, flat, irregular or sesamoid - all bones are made up of: a compact or cortical bone, a sponge or
cancellous bone, an external tissue layer called periosteum, an internal tissue layer called endosteum and the bone marrow which is part of the lymphatic system.
The muscular system
The term 'muscle' refers to all the contractile tissues of the body: skeletal, cardiac and smooth muscle . The muscular system, however, refers only to the skeletal muscle system and not to the heart - which is considered to be part of the cardiovascular system - or the smooth muscle of the intestine - which is part of the digestive system.
Through sustained contraction or alternating contraction and relaxation, muscle tissue has three main functions:
- producing motion, such as walking and running1;
- providing stability, such as standing or sitting;
- generating heat to maintain body temperature.
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1 A baby's body has about 300 bones at birth. These eventually grow together to form the 206 bones that adults have.
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1 Besides walking and running, what other types of motion can muscles provide?