A slight elevation may be present along the sagittal suture, but tends to be poorly developed in modern man. The temporal lines continue from the frontal bone onto the parietals, representing areas of muscle attachment. It should be noted that the lambdoidal suture has a beveled-concave surface on the parietal bones. Posteriorly the parietals articulate with the occipital bone at the lambdoidal suture and laterally at its squamous margin with the temporal bones. The bregmatic fontanelle or “anterior soft spot” exists here in infancy. The coronal and sagittal suture intersect at a point called bregma. They articulate with one another medially at the sagittal suture and anteriorly with the frontal bone at the coronal suture. The parietals are paired bones which form the roof and sides of the calvaria. The paired temporal lines ascend superiorly and posteriorly from the zygomatic processes and constitute the superior-anterior margin of the temporal fossae. The median crest in the midline of the bone represents an area of muscle attachment and shows variability reflecting muscular robusticity of the individual. These prominences may vary in size and degree of development in individuals and are also a characteristic of sexual dimorphism. The frontal eminences are paired prominences in the anterolateral regions of the squamous portion of the frontal bone. The glabella is a roughened region or a bulging prominence on the frontal bone above the nasal root at about the level of the supraorbital ridges. The supraorbital notches or foramina are grooves or openings for the passage of neurovascular structures.Ī trace of the metopic or frontal suture may be noted in the midsagittal region of this bone. These bony ridges are quite well developed in the skulls of some forms of fossil man, but are less pronounced in modern man. The supraorbital or brow ridges are bony ridges just above the orbits. The frontal is a single bone which is comprised of two main parts, a squamous or flat portion which forms the forehead and articulates with the parietal bones and an orbital portion which provides a roof for the two orbits. You should familiarize yourself with each of their distinguishing morphological features. Each of the flat bones of the skull will now be reviewed individually. The areas of bone thickening or ridging generally reveal the points of muscle or ligamentous attachment. The inner and outer layers tend to run parallel to one another and the bones are somewhat rounded with the inner layer being concave. These comprise the outer and inner layers of compact bone and an intervening layer of spongy, cancellous bone called diploe. The flat bones of the skull making up the neurocranium or braincase have three basic structural layers. The face includes the following 14 bones:įlat Bones of the Skull: Frontal, Parietal, Occipital, and Temporal The cranial vault includes the following 8 bones: The human skull is comprised of a total of 22 separate bones (excluding the ear ossicles and hyoid bone).
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