The parietal bones (Latin : ossa parietalia, verticis, bregmatis ; french : os pariétal) form a principal part of the roof of the skull; they are of a square form, convex externally, concave internally, and present each two surfaces and four borders. The external surface, rises towards its middle, where it presents a slight elevation, called the parietal eminence, 5 below which is a curved line, forming part of the temporal ridge, and bounding a flat surface (planum semicirculare), which forms a part of the temporal fossa. At the upper and back part of the bone, usually about two lines from the sagittal suture, is a small hole, 6 (foramen parietale) which transmits a communicating vein; its position is exceedingly variable; even its existence is not constant.
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The occipital bone, (lat.: os occipitis, french: Os occipital) is situated at the posterior part of the base of the skull; broad behind, much narrowed before, of a trapezoid figure, presenting two surfaces, four borders, and four angles. To place the bone in its natural position, hold it so that the great foramen and the articulating processes beside it shall look directly downwards; the thick process in front of the foramen will then project forwards into the base of the Skull, Whilst the broad expanded part behind it arches upwards and a little forwards, forming the posterior wall of the Cavity.
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The vomer bone (Fench: le Vomer) is an irregular four-sided plate of bone constituting the lower portion of the nasal septum. It is usually described as resembling a ploughshare in shape. Each lateral surface is covered with the thick mucous membrane of the nasal sinus, and is traversed by a narrow but well-marked groove, which lodges the naso- palatine nerve from the spheno-palatine ganglion; hence it is sometimes called the naso-palatine groove.
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The ethmoid (french: ethmoide) is a bone of delicate texture, situated at the anterior part of the skull-base; it is roughly cuboidal in shape, and its delicacy is due to the fact that it is honeycombed by air-cells. The bone consists of four parts: the horizontal or cribriform plate, two lateral masses, and a perpendicular plate.
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The frontal bone, (os frontis, coroaale,) situated at the anterior part of the skull, and upper part of the face, is divisible into two parts (frontal and orbital), differing in size and position: of these, one extends upwards towards the vertex, forming three-fourths of the extent of the bone; the other, inferior and horizontal in its direction, forms the roof of the orbits. To place the bone in its natural position, hold it so that the orbital plates shall look downwards, and the smooth convex surface forwards.
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The bones which form the appendicular elements of the skullis group are the mandible (lower jaw), malleus, incus, stapes, hyoid, the styloid process of the temporal bone, and the internal pterygoid process of the sphenoid.
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