General Anatomy: Skeleton System

Cartilaginous bones ossify in cartilage (endochondral ossification) and develop from preformed cartilaginous models, as seen in limb bones.

The axial skeleton includes the skull, vertebral column, and thoracic cage, providing the central support framework of the body.

Modified long bones, like the clavicle, lack a medullary cavity and have unique structural adaptations compared to typical long bones.

Sesamoid bones, such as the patella, resist pressure, reduce friction, alter muscle pull direction, and maintain circulation in tendons.

Irregular bones have complex shapes and include the vertebrae, hip bones, and some skull bones.

Sesamoid bones are embedded in tendons or joint capsules, lack periosteum, and help resist pressure and minimize friction. The patella is a common example.

Pneumatic bones, such as the maxilla, sphenoid, and ethmoid, contain air spaces that reduce skull weight and help in voice resonance and air filtration.

Flat bones resemble shallow plates and form boundaries of body cavities. Examples include the ribs, sternum, scapula, and skull bones.

Miniature long bones, such as metacarpals, metatarsals, and phalanges, have only one epiphysis.

Typical long bones have an elongated shaft and two expanded ends. Examples include the humerus, radius, ulna, femur, tibia, and fibula.

Bone can remodel itself based on stress and strain, showing atrophy when not used and hypertrophy when subjected to repeated use.

The bone marrow contains reticuloendothelial cells, which are phagocytic and help in immune responses by removing harmful substances.

Collagen fibers, which are part of the organic connective tissue, make the bone tough and resilient, allowing it to withstand tensile forces.

The inorganic calcium salts, mainly calcium phosphate and calcium carbonate, make the bone hard and rigid, enabling it to resist compressive forces.

The skeleton forms the main supporting framework of the body and is designed for effective movement with the help of attached muscles.

The vertical axis runs from head to toe through the body.

Movements always happen parallel to the plane in which they take place.

A skater's spin happens around the vertical axis, as it involves rotation along the body's length.

The three movement axes are the frontal axis, sagittal axis, and vertical axis.