An immobile or nearly immobile joint is called a synarthrosis. The immobile nature of these joints provide for a strong union between the articulating bones. This is important at locations where the bones provide protection for internal organs. Examples include sutures, the fibrous joints between the bones of the skull that surround and protect the brain (Picture 1), and the manubriosternal joint, the cartilaginous joint that unites the manubrium and body of the sternum for protection of the heart.