![]() The face is composed of 14 bones that are all separated from each other by sutures, as in the cranium. Ethmoid sinus – in the ethmoid bones, behind the nasal cavity.Mastoid process – in the temporal bones, beneath the positions of the ears. ![]() Frontal sinus – in the central portion of the frontal bone, between the positions of the eyebrows.Some of the bony processes listed and their positions on the skull are shown in Figure 7.3.Īlthough the cranium is mainly a hollowed out cavity enclosing the brain, the head itself would be too heavy to lift by the neck muscles if the bones were solid.Ĭonsequently, several of them contain air-filled sinuses that reduce the overall weight of the head, allowing it to be held upright and looking forwards. Bony processĬontains air-filled spaces of the mastoid sinus and allows attachment of large neck muscleĮxtends into medial and lateral plates for attachment of muscles of masticationĪttachment for neck muscle associated with chewing and swallowing actionsįorms portion of zygomatic arch and allows attachment of muscle of mastication Those with particular relevance to dentistry are shown in Table 7.2. In addition to these bony openings, some cranial bones also have various projections and plates present on their outer surfaces, which serve as attachments for ligaments and muscles associated with head and jaw movements, or which form part of facial structures. Some of the bony openings are listed and their positions on the underside of the cranium are shown in Figure 7.2. Glossopharyngeal nerve (cranial nerve IX) Internal acoustic meatus (inner ear canal) Mandibular division of trigeminal nerve (cranial nerve V) Other foramina of the cranium with particular relevance to dentistry are shown in Table 7.1. The largest foramen of all is the foramen magnum, which opens through the occipital bone, and allows the exit of the spinal cord from the base of the brain and into the vertebral column of the spine. Similarly, all of the blood vessels supplying the head and neck structures pass through these same foramina or between natural spaces between adjacent bones, called fissures. The main function of the cranium is to encase and protect the brain.Īll of the sensory nerve cells running from the body to the brain, and all of the motor nerves running from the brain to the body have to pass in and out of this bony cavity, and they do so through many natural openings in the underside of the cranium, called foramina (singular – foramen). Reproduced with permission from John Wiley & Sons, Ltd.) Levison’s Textbook for Dental Nurses, 10th edn. ![]() The skull and cranial bones are illustrated in Figure 7.1.įigure 7.1 Skull and cranial bones. Ethmoid bone – single plate at the lower front of the cranium, immediately behind the nose.Sphenoid bone – single plate forming the majority of the base of the cranium.Occipital bone – single plate at the back and partial underside of the cranium. ![]()
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