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The full complement of bones of the tetrapod skull roof, as seen in the temnospondyl Xenotosuchus. The skull roof or the roofing bones of the skull are a set of bones covering the brain, eyes and nostrils in bony fishes and all land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium.
It forms the main component of the skull roof. The calvaria is made up of the superior portions of the frontal bone, occipital bone, and parietal bones. [1] In the human skull, the sutures between the bones normally remain flexible during the first few years of postnatal development, and fontanelles are palpable.
It is composed of 270 bones at the time of birth, [2] but later decreases to 206: 80 bones in the axial skeleton and 126 bones in the appendicular skeleton. 172 of 206 bones are part of a pair and the remaining 34 are unpaired. [3] Many small accessory bones, such as sesamoid bones, are not included in this.
The facial skeleton comprises the facial bones that may attach to build a portion of the skull. [1] The remainder of the skull is the neurocranium.. In human anatomy and development, the facial skeleton is sometimes called the membranous viscerocranium, which comprises the mandible and dermatocranial elements that are not part of the braincase.
The axial skeleton (80 bones) is formed by the vertebral column (32–34 bones; the number of the vertebrae differs from human to human as the lower 2 parts, sacral and coccygeal bone may vary in length), a part of the rib cage (12 pairs of ribs and the sternum), and the skull (22 bones and 7 associated bones).
1 occipital bone; 2 parietal bones; 1 sphenoid bone; 2 temporal bones; The ossicles (three on each side) are usually not included as bones of the neurocranium. [6] There may variably also be extra sutural bones present. Below the neurocranium is a complex of openings and bones, including the foramen magnum which houses
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The sphenoid bone [note 1] is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the basilar part of the occipital bone. The sphenoid bone is one of the seven bones that articulate to form the orbit. Its shape somewhat resembles that of a butterfly, bat or wasp with its wings extended.