iskelet

Iskelet is the internal framework that provides support, shape and protection for an organism. In humans it comprises bones, cartilage, joints and connective tissues and is divided into the axial skeleton (skull, spine, rib cage) and the appendicular skeleton (limbs and girdles). An adult typically has around 206 bones, though this number can vary among individuals.

Bones are living tissue with a mineralized matrix of collagen fibers and hydroxyapatite. They contain bone marrow within cavities and form joints with cartilage. Ligaments connect bones, while tendons attach muscles to bones. Cartilage covers the ends of bones at joints to reduce friction and absorb shock.

Bones develop by intramembranous and endochondral ossification. Growth in length occurs at the epiphyseal plates during childhood and adolescence; once these plates close, longitudinal growth ends. Throughout life, bone tissue is remodeled by the coordinated actions of osteoblasts and osteoclasts, balancing formation and resorption.

The isklet serves several key functions: it provides structural support and posture, protects vital organs (for example the skull protecting the brain and the rib cage protecting the heart and lungs), enables movement in concert with muscles, stores minerals such as calcium and phosphate, and houses bone marrow for blood cell production.

Maintaining skeletal health depends on nutrition, physical activity and absence of disease. Common issues include osteoporosis and fractures, osteoarthritis, scoliosis or congenital bone disorders. Evolutionarily, vertebrate skeletons arose from cartilage-like tissue and diversified into endoskeletons and, in many invertebrates, exoskeletons.