Beneath each superciliary arch is a curved and prominent margin, the supraorbital margin, which forms the upper boundary of the base of the orbit, and separates the squama from the orbital portion of the bone. The lesser wings project laterally and form the floor of the anterior cranial fossa and the superior orbital fissure through which several key optical nerves pass. The spine forms part of the septum of the nose, articulating in front with the crest of the nasal bones and behind with the perpendicular plate of the ethmoid. The posterior borders of the orbital plates are thin and serrated, and articulate with the small wings of the sphenoid. They form part of the medial wall of the orbit. The squamous part of the frontal bone houses the frontal sinuses, which are separated by a septum and are located above the orbits.
The frontal articulates with twelve bones: the sphenoid, the ethmoid, the two parietals, the two nasals, the two maxillæ, the two lacrimals, and the two zygomatics. From the center of the notch the nasal process projects downward and forward beneath the nasal bones and frontal processes of the maxillæ, and supports the bridge of the nose. The neurocranium forms the cranial cavity that surrounds and protects the brain and brainstem. Sphenoid Bone The sphenoid bone is situated in the middle of the skull towards the front and forms the rear of the orbit. The Mandible Finally, the mandible forms the lower jaw of the skull. Mandible Known as the lower jaw bone.
Bones of the Cranium Ethmoid Floor of the cranium, inferior to the frontal bone and anterior to the sphenoid. The range in the capacity of the cranial cavity is wide but is not directly proportional to the size of the skull, because there are variations also in the thickness of the bones and in the size of the air pockets, or sinuses. The central nervous system lies largely within the axial skeleton, the being well protected by the cranium and the by the vertebral column, by means of the bony neural arches the arches of bone that encircle the spinal cord and the intervening ligaments. Form the bottom of the orbitals and nasal cavities, and also the roof of the mouth. The glabella is a smooth elevation on the frontal bone, a landmark between the two superciliary arches.
Vomer Thin roughly triangular plate of bone on the floor of the nasal cavity and part of the nasal septum. The lateral part of this margin is sharp and prominent, affording to the eye, in that situation, considerable protection from injury; the medial part is rounded. Evolutionary,it is the expansion of the neurocranium that has facilitated the expansion of the brain and its associated developments. Paranasal Sinuses Definition: air-filled cavities lined with mucous membranes located within some skull bones. Two major muscles of the face — the temporalis and orbicularis oculi — form origins on the frontal bone.
In order to accommodate bloodflow to the eyes, small notches or openings known as orbital foramina are located near the eye sockets. The two major fontanelles are the frontal fontanelle located at the junction of the coronal and sagittal sutures and the occipital fontanelle located at the junction of the sagittal and lambdoid sutures. Two small holes, known as the supraorbital foramina, are found above each orbit in the supraorbital ridge and provide exit points to the forehead for the supraorbital nerve and the supraorbital artery. Nasal Bones The two slender nasal bones located in the midline of the face fuse to form the bridge of the noise and also articulate with the frontal, ethmoid and maxilla bones. The more anterior one is the sphenoidal between the sphenoid, parietal, temporal, and frontal bones , while the more posterior one is the mastoid between the temporal, occipital, and parietal bones. Finally, the small and inferior tympanic region lies anteriorly to the mastoid.
The much larger, diamond-shaped anterior fontanelle—where the two frontal and two parietal bones join—generally remains open until a child is about two years old. On either side of the middle line the bone presents depressions for the convolutions of the brain, and numerous small furrows for the anterior branches of the middle meningeal vessels. Foramina inside the body of humans and other animals typically allow muscles, nerves, arteries, veins, or other structures to connect one part of the body with another. Beneath each superciliary arch is a curved and prominent margin, the , which forms the upper boundary of the base of the , and separates the squamous part from the orbital portion of the bone. Deep to the supraorbital ridges is a pair of hollow spaces known as the frontal sinuses. Parietal Top and sides of the cranium, posterior roof of the skull.
Both orbital plates are divided from every other by U-shaped ethmoidal notch for adapting of the. There are typically in the body, though there may be up to about 226. The biggest part of the frontal bone is under the forehead. It is one of eight bones that form the cranium, or brain case. The neurocranium consists of the occipital bone, two temporal bones, two parietal bones, the sphenoid, ethmoid, and frontal bones—all are joined together with sutures.
Bone into which the lower teeth are attached. On either side of the middle line the bone presents depressions for the convolutions of the brain, and numerous small furrows for the anterior branches of the middle meningeal vessels. Development of cranial bones The cranium is formed of bones of two different types of developmental origin—the cartilaginous, or substitution, bones, which replace preformed in the general shape of the bone; and membrane bones, which are laid down within layers of. Lacrimal Behind and lateral to the nasal bone, also contribute to the orbits. It presents a nasal notch, which articulates inferiorly with the 2 nasal bones 1 on every side of median plane and laterally on every side with and the.