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The skull is composed of three types of bone: cranial bones, facial bones and ossicles, which is made up of a number of fused flat and irregular bones. The cranial bones are joined at firm fibrous junctions called sutures and contains many foramina, fossae, processes, and sinuses.
The head rests on the top part of the vertebral column, with the skull joining at C1 (the first cervical vertebra known as the atlas). The skeletal section of the head and neck forms the top part of the axial skeleton and is made up of the skull, hyoid bone, auditory ossicles, and cervical spine. The skull can be further subdivided into:
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. Premature complete ossification of these sutures is called craniosynostosis.
In anatomy, a suture is a fairly rigid joint between two or more hard elements of an organism, with or without significant overlap of the elements. [ 1 ] Sutures are found in the skeletons or exoskeletons of a wide range of animals, in both invertebrates and vertebrates .
Side view of the skull Human skull side sutures right. A suture is a type of fibrous joint that is only found in the skull (cranial suture). The bones are bound together by Sharpey's fibres. A tiny amount of movement is permitted at sutures, which contributes to the compliance and elasticity of the skull. These joints are synarthroses. [1]
It lies at the junction between the sagittal suture and lambdoid suture. At birth, the skull features a small posterior fontanelle with an open area covered by a tough membrane, where the two parietal bones adjoin the occipital bone (at the lambda). The posterior fontanelles ossify within 6–8 weeks after birth.
The cranial cavity, also known as intracranial space, is the space within the skull that accommodates the brain.The skull is also known as the cranium. [1] The cranial cavity is formed by eight cranial bones known as the neurocranium that in humans includes the skull cap and forms the protective case around the brain.
Instead, the skull is composed of loosely jointed bones. The cranial vault as a distinct unit arose with the fusion of the skull roof and the endocranium on the early Labyrinthodonts . [ 2 ] In amphibians and reptiles , the vault is rather small and inconspicuous, only forming proper vaults in mammals and birds .