Churchill Livingstone. Read it at Google Books - Find it at Amazon. Related articles: Anatomy: Head and neck. Promoted articles advertising. Figure 1: skull and facial bones illustrations Figure 1: skull and facial bones illustrations. Figure 2: skull and facial bones illustrations Figure 2: skull and facial bones illustrations. Figure 3: skull and facial bones illustrations Figure 3: skull and facial bones illustrations.
Figure 3: lateral view Gray's illustrations Figure 3: lateral view Gray's illustrations. Figure 5: medial view Gray's illustrations Figure 5: medial view Gray's illustrations. Loading more images Close Please Note: You can also scroll through stacks with your mouse wheel or the keyboard arrow keys.
Loading Stack - 0 images remaining. The flattened, upper portion is the squamous portion of the temporal bone.
Below this area and projecting anteriorly is the zygomatic process of the temporal bone, which forms the posterior portion of the zygomatic arch. Posteriorly is the mastoid portion of the temporal bone. Projecting inferiorly from this region is a large prominence, the mastoid process , which serves as a muscle attachment site. The mastoid process can easily be felt on the side of the head just behind your earlobe.
Posterior to the mandibular fossa on the external base of the skull is an elongated, downward bony projection called the styloid process, so named because of its resemblance to a stylus a pen or writing tool. This structure serves as an attachment site for several small muscles and for a ligament that supports the hyoid bone of the neck.
See also Figure 6. The frontal bone is the single bone that forms the forehead. At its anterior midline, between the eyebrows, there is a slight depression called the glabella see Figure 6. The frontal bone also forms the supraorbital margin of the orbit.
Near the middle of this margin, is the supraorbital foramen, the opening that provides passage for a sensory nerve to the forehead. The frontal bone is thickened just above each supraorbital margin, forming rounded brow ridges. These are located just behind your eyebrows and vary in size among individuals, although they are generally larger in males. Inside the cranial cavity, the frontal bone extends posteriorly. This flattened region forms both the roof of the orbit below and the floor of the anterior cranial cavity above see Figure 6.
The occipital bone is the single bone that forms the posterior skull and posterior base of the cranial cavity Figure 6. On the base of the skull, the occipital bone contains the large opening of the foramen magnum , which allows for passage of the spinal cord as it exits the skull. On either side of the foramen magnum is an oval-shaped occipital condyle. These condyles form joints with the first cervical vertebra and thus support the skull on top of the vertebral column.
The sphenoid bone is a single, complex bone of the central skull Figure 6. The sphenoid forms much of the base of the central skull and also extends laterally to contribute to the sides of the skull see Figure 6.
Inside the cranial cavity, the right and left lesser wings of the sphenoid bone , which resemble the wings of a flying bird, form the lip of a prominent ridge that marks the boundary between the anterior and middle cranial fossae.
This bony region of the sphenoid bone is named for its resemblance to the horse saddles used by the Ottoman Turks, with a high back and a tall front. The rounded depression in the floor of the sella turcica is the hypophyseal pituitary fossa , which houses the pea-sized pituitary hypophyseal gland. The greater wings of the sphenoid bone extend laterally to either side away from the sella turcica, where they form the anterior floor of the middle cranial fossa. The greater wing is best seen on the outside of the lateral skull, where it forms a rectangular area immediately anterior to the squamous portion of the temporal bone.
On the inferior aspect of the skull, each half of the sphenoid bone forms two thin, vertically oriented bony plates. The right and left medial pterygoid plates form the posterior, lateral walls of the nasal cavity. The somewhat larger lateral pterygoid plates serve as attachment sites for chewing muscles that fill the infratemporal space and act on the mandible. The ethmoid bone is a single, midline bone that forms the roof and lateral walls of the upper nasal cavity, the upper portion of the nasal septum, and contributes to the medial wall of the orbit Figure 6.
On the interior of the skull, the ethmoid also forms a portion of the floor of the anterior cranial cavity.
Within the nasal cavity, the perpendicular plate of the ethmoid bone forms the upper portion of the nasal septum. The ethmoid bone also forms the lateral walls of the upper nasal cavity. Extending from each lateral wall are the superior nasal concha and middle nasal concha, which are thin, curved projections that extend into the nasal cavity Figure 6.
In the cranial cavity, the ethmoid bone forms a small area at the midline in the floor of the anterior cranial fossa. This region also forms the narrow roof of the underlying nasal cavity. This portion of the ethmoid bone consists of two parts, the crista galli and cribriform plates. It functions as an anterior attachment point for one of the covering layers of the brain. Small nerve branches from the olfactory areas of the nasal cavity pass through these openings to enter the brain.
A suture is an immobile joint between adjacent bones of the skull. The narrow gap between the bones is filled with dense, fibrous connective tissue that unites the bones. The long sutures located between the bones of the brain case are not straight, but instead follow irregular, tightly twisting paths.
These twisting lines serve to tightly interlock the adjacent bones, thus adding strength to the skull for brain protection. The two suture lines seen on the top of the skull are the coronal and sagittal sutures.
The coronal suture runs from side to side across the skull, within the coronal plane of section see Figure 6. It joins the frontal bone to the right and left parietal bones.
The sagittal suture extends posteriorly from the coronal suture, running along the midline at the top of the skull in the sagittal plane of section see Figure 6.
It unites the right and left parietal bones. On the posterior skull, the sagittal suture terminates by joining the lambdoid suture. The lambdoid suture extends downward and laterally to either side away from its junction with the sagittal suture. The lambdoid suture joins the occipital bone to the right and left parietal and temporal bones.
The squamous suture is located on the lateral skull. It unites the squamous portion of the temporal bone with the parietal bone see Figure 6. The facial bones of the skull form the upper and lower jaws, the nose, nasal cavity and nasal septum, and the orbit. The facial bones include 14 bones, with six paired bones and two unpaired bones. The neurocranium is comprised of eight bones: occipital, two temporal bones, two parietal bones, sphenoid, ethmoid, and the frontal bone.
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. Evolutionary,it is the expansion of the neurocranium that has facilitated the expansion of the brain and its associated developments.
Neurocranium : A lateral view showing the bones that structure the neurocranium. The occipital bone forms the base of the skull at the rear of the cranium. It articulates with the first vertebra of the spinal cord and also contains the foramen magnum, the large opening of the skill through which the spinal cord passes as it enters the vertebral column. The occipital bone borders the parietal bones through the heavily serrated lambdoidal suture, and also the temporal bones through occipitomastoid suture.
The temporal bones are situated at the base and sides of the skull, lateral to the temporal lobes of the brain. The temporal bones consist of four regions the squamous, mastoid, petrous and tympanic regions. The squamous region is the largest and most superior region. Inferior to the squamous is the mastoid region, and fused between the squamous and mastoid regions is the petrous region.
Finally, the small and inferior tympanic region lies anteriorly to the mastoid. The two large parietal bones are connected and make up part of the roof and sides of the human skull. The two bones articulate to form the sagittal suture. In the front, the parietal bones form the coronal suture with the frontal bone, and in the rear, the lambdoid suture is formed by the occipital bone.
Finally, the squamosal suture separates the parietal and temporal bones. The sphenoid bone is situated in the middle of the skull towards the front and forms the rear of the orbit. It has been described as resembling a butterfly due to its wing-like processes. The sphenoid bone is divided into several parts: the body of the bone, two greater wings, two lesser wings, and the pterygoid processes.
The sphenoid bone is one of the most complex in the body due to its interactions with numerous facial bones, ligaments, and muscles. The body that forms the middle of the sphenoid bone articulates with the ethmoid and occipital bone and forms a key part of the nasal cavity; it also contains the sphenoidal sinuses. The greater wings form the floor of the middle cranial fossa that houses the frontal lobes and pituitary gland, and also the posterior wall of the orbit.
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 ethmoid bone is a small bone in the skull that separates the nasal cavity from the brain. It is lightweight due to its spongy, air-filled construction and is located at the roof of the nose and between the two orbits. The ethmoid bone forms the medial wall of the orbit, the roof of the nasal cavity, and due to its central location it articulates with numerous bones of the viscerocranium.
Inside the neurocranium it articulates with the frontal and sphenoid bones. The frontal bone borders two other neurocranial bones—the parietal bones through the coronal sutures and the sphenoid bone through the sphenofrontal suture.
It also articulates with the zygomatic and nasal bones and the maxilla. The viscerocranium face includes these bones: vomer, 2 inferior nasal conchae, 2 nasals, maxilla, mandible, palatine, 2 zygomatics, and 2 lacrimals. The viscerocranium or facial bones supports the soft tissue of the face. The viscerocranium consists of 14 individual bones that fuse together.
However, the hyoid bone, ethmoid bone, and sphenoid bones are sometimes included in the viscerocranium. The two zygomatic bones form the cheeks and contribute to the orbits. They articulate with the frontal, temporal, maxilla, and sphenoid bones. The two lacrimal bones form the medial wall of the orbit and articulate with the frontal, ethmoid, maxilla, and inferior nasal conchae. The lacrimal bones are the two smallest bones located in the face. 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 inferior nasal conchae are located within the nasal cavity. They are spongy and curled in shape; their primary function is to increase the surface area of the nasal cavity, which also increases the amount of air that contacts the mucous membranes and cilia of the nose, thus filtering, warming, and humidifying the air before it enters the lungs.
At the base of the nasal cavity is the small vomer bone which forms the nasal septum. The maxilla bones fuse in the midline and form the upper jaw. They provide the bed for the upper teeth, the floor of the nose, and the base of the orbits. The maxilla articulates with the zygomatic, nasal, lacrimal, and palatine bones.
The palatine bones fuse in the midline to form the palatine, located at the back of the nasal cavity that forms the roof of the mouth and the floor of the orbit. Finally, the mandible forms the lower jaw of the skull. The joint between the mandible and the temporal bones of the neurocranium, known as the temporomandibular joint, forms the only non-sutured joint in the skull. Facial bones : There are fourteen facial bones.
Some, like the lacrimal and nasal bones, are paired. Others, like the mandible and vomer, are singular. The orbit, or eye socket, is the cavity located in the skull in which the eye and its associated appendages are housed. The orbits are conical, sometimes described as four-sided pyramidal, cavities that open in the midline of the face and point backwards.
To the rear of the orbit, the optic foramen opens into the optical canal through which the optic nerve and ophthalmic artery pass. The primary functions of the orbit include protection of its delicate contents and, through muscle attachment and a smooth coating fascia, to also promote the smooth, delicate movements of the eye.
The orbital cavity is formed from seven bones. The frontal bone forms the superior border of the orbital rim and also the superior wall roof of the orbital surface. The zygomatic bone forms the lateral and half of the basal border of the orbital rim, and also the lateral wall of the orbital surface—this is the thickest region of the orbit as it is most exposed to external trauma. Completing the basal and medial border of the orbital rim is the maxillary bone, which also forms the inferior wall floor of the orbital surface.
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