A bony joint, or synostosis8 (SIN-oss-TOE-sis), is a joint in which two bones, once separate, have become fused by osseous tissue and in most cases are then regarded as a single bone. Some fibrous and cartilaginous joints ossify with age—that is, the gap between adjacent bones becomes filled with osseous tissue until the two bones appear as one. In the skull, for example, both the frontal bone and mandible are represented at birth by separate right and left bones; in early childhood, these bones become fused. In old age, some sutures become obliterated by ossification and adjacent cranial bones fuse seamlessly together. The epiphyses and dia-physes of the long bones are joined by cartilaginous joints in childhood and adolescence, and these become synos-toses in early adulthood. The attachment of the first rib to the sternum also becomes a synostosis with age.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.