Luusto

Luosto, the Finnish term for the skeletal system, refers to the body's internal framework that supports, protects, and enables movement. In humans, it comprises bones, cartilage, ligaments, tendons around joints, and the bone marrow within certain bones. The adult human skeleton typically consists of about 206 bones, distributed into the axial skeleton (skull, vertebral column, rib cage) and the appendicular skeleton (the limbs and girdles).

Bone tissue comes in two main types: compact bone, which forms the dense outer layer, and cancellous (spongy) bone inside the ends of long bones and in the interiors of others. Bones are living tissues that grow, remodel, and repair themselves through the actions of osteoblasts, osteocytes, and osteoclasts, in a continuous cycle influenced by hormones, mechanical load, and nutrition. Bone marrow resides within certain bones; in adults red marrow produces blood cells, while yellow marrow stores fat.

Developmentally, most bones arise by endochondral ossification, where cartilage templates are replaced by bone, while some flat bones form by intramembranous ossification. Growth in length occurs at the epiphyseal plates during childhood and adolescence, eventually closing in adulthood. Joints, or articulations, enable movement through the connections between bones, aided by cartilage, ligaments, and tendons.

Functions of Luusto include support and shape, protection of internal organs, facilitation of movement in conjunction with muscles, storage of minerals such as calcium and phosphate, and hematopoiesis in red bone marrow. The system also contributes to endocrine regulation through bone-derived hormones. Common disorders include osteoporosis, which weakens bone and increases fracture risk, fractures from trauma, and degenerative joint diseases such as osteoarthritis.