GE 345: Week 8

Skeletal System

    Physiology/Kinesiology

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[ Bone ] [ Skeleton ] [ Terms ]
[ Articulations ] [ Stability & Movement ]

The Skeletal System

The skeletal system consists of bone and cartilage, which provide the body's framework. Bones are important for movement, support, protection, and mineral storage.

• Bones are the levers that move around the axes (articulations or joints), of which muscles, which are activated by the nervous system, provide the force.
• Bones are the framework for our bodies, supporting soft tissues and contributing to body form.
• Bones protect vital organs by surrounding them with a hard "casing."
• Calcium and phosporous are stored in the bones.

When considered as a whole, the system provides a balance of stability and freedom of movement, allowing the individual to constantly adjust to shifting of the base of support and center of gravity.

Basic bone structures include: long bones, such as the femur and humerus, which are basically long tubes with a medullary (marrow) cavity along the middle; short bones such as the digits; flat bones such as the scapulae; and irregular bones such as the carpal and tarsal bones.

The bone itself may be compact or cancellous (spongy), or some combination of the two.

Bone is constantly being absorbed (broken down) and formed:

• Osteoclasts: release proteolytic enzymes from their lysosomes, believed to digest the bone's organic matric, and several acids, which cause solution of the bone salts.
• Osteoblasts: secrete collagen and other substances which forms the foundation for bone development by providing a structure for precipitation of calcium salts.

In children, bone formation occurs at a higher rate. In adults, these rates are about the same. In the elderly, bone deposition declines. Typically, bone adjusts its strength porportionally to its stresses. It thickens when subjected to heavy loads, and its shape can be rearranged for proper support. It also develops new matrices as the old matrices degenerate. Bone deposition is proportional to compressional loads to which the bone is subjected.

When a bone breaks, many new osteoblasts are created to form a new bone matrix.

[ Bone ] [ Skeleton ] [ Terms ]
[ Articulations ] [ Stability & Movement ]