Occipital Bone: Part of the back and base of the CRANIUM that encloses the FORAMEN MAGNUM.Skull Neoplasms: Neoplasms of the bony part of the skull.Parietal Bone: One of a pair of irregularly shaped quadrilateral bones situated between the FRONTAL BONE and OCCIPITAL BONE, which together form the sides of the CRANIUM.Foramen Magnum: The large hole at the base of the skull through which the SPINAL CORD passes.Atlanto-Occipital Joint: The point of articulation between the OCCIPITAL BONE and the CERVICAL ATLAS.Skull: The SKELETON of the HEAD including the FACIAL BONES and the bones enclosing the BRAIN.Cervical Atlas: The first cervical vertebra.Skull Base: The inferior region of the skull consisting of an internal (cerebral), and an external (basilar) surface.Bone and Bones: A specialized CONNECTIVE TISSUE that is the main constituent of the SKELETON. The principle cellular component of bone is comprised of OSTEOBLASTS; OSTEOCYTES; and OSTEOCLASTS, while FIBRILLAR COLLAGENS and hydroxyapatite crystals form the BONE MATRIX.Cranial Fossa, Posterior: The infratentorial compartment that contains the CEREBELLUM and BRAIN STEM. It is formed by the posterior third of the superior surface of the body of the sphenoid (SPHENOID BONE), by the occipital, the petrous, and mastoid portions of the TEMPORAL BONE, and the posterior inferior angle of the PARIETAL BONE.Bone Remodeling: The continuous turnover of BONE MATRIX and mineral that involves first an increase in BONE RESORPTION (osteoclastic activity) and later, reactive BONE FORMATION (osteoblastic activity). The process of bone remodeling takes place in the adult skeleton at discrete foci. The process ensures the mechanical integrity of the skeleton throughout life and plays an important role in calcium HOMEOSTASIS. An imbalance in the regulation of bone remodeling's two contrasting events, bone resorption and bone formation, results in many of the metabolic bone diseases, such as OSTEOPOROSIS.Bone Density: The amount of mineral per square centimeter of BONE. This is the definition used in clinical practice. Actual bone density would be expressed in grams per milliliter. It is most frequently measured by X-RAY ABSORPTIOMETRY or TOMOGRAPHY, X RAY COMPUTED. Bone density is an important predictor for OSTEOPOROSIS.Tomography, X-Ray Computed: Tomography using x-ray transmission and a computer algorithm to reconstruct the image.