skeleti

Skeleti, often used to refer to the skeletal system of vertebrates, is the internal framework that supports and shapes an organism. It comprises bones, cartilage, ligaments, tendons, and joints, with bone marrow producing blood cells in many species.

In vertebrates, the skeleton is divided into the axial skeleton, which includes the skull, spine, and rib cage, and the appendicular skeleton, which comprises the limbs and girdles. Some species also possess specialized skeletal structures, such as beaks or dermal ossifications, that supplement or replace bones in certain regions.

Bones form through ossification, by intramembranous or endochondral processes, and grow during development. Throughout life, bone tissue is remodeled by osteoblasts and osteoclasts to adapt to use and repair microdamage.

The skeleton supports the body, facilitates movement via joints and muscle attachments, protects vital organs, and stores minerals, particularly calcium and phosphorus. The bone marrow within certain bones also manufactures blood cells in many animals.

Skeletons vary widely among organisms. In humans and many other vertebrates, the axial and appendicular divisions reflect function and organization, while other phyla may have exoskeletons or other protective frameworks.

Health and development of the skeleti are influenced by nutrition (calcium, vitamin D), physical activity, hormones, and genetics. Disorders can include osteoporosis, fractures, arthritis, and congenital deformities.

See also: Osteology, skeletal system, bone remodeling.