124 Anatomy & Physiology Essentials Copyright Goodheart-Willcox Co., Inc. • carotid canal—a tunnel through which the internal carotid artery, (the major source of blood to the brain), passes Facial Bones A total of fourteen bones form the face, including the mandible, vomer, and six pairs (left and right) of bones. • The two fused maxillary bones, which form the upper jaw, house the upper teeth in the alveolar process, and connect to all other bones of the face, with the exception of the mandible. • The two palatine bones form the posterior part of the hard palate, or roof of the mouth, and include the paranasal sinuses, which amplify sounds from the vocal chords and reduce the weight of the head. • The two zygomatic bones, or cheekbones, also form much of the sides of the orbits, or eye sockets. • The two lacrimal bones are tiny bones connecting to the orbits and surrounding the tear ducts. • The two nasal bones form the bridge of the nose. • The vomer (plow-shaped) bone comprises most of the bony nasal septum. • The two inferior concha bones form the sides of the nasal cavity. • The mandible, or lower jaw bone, is the largest facial bone, as well as the only movable facial bone, housing the lower teeth within the alveolar process. • The hyoid bone, which is located in the mid-neck just above the larynx, is linked by ligaments to the styloid process of the temporal bones, and forms a moving base for the tongue as well as an attachment site for the muscles that raise and lower the larynx when a person swallows. • The occipital bone forms the base and lower back portions of the skull. It joins to the parietal bones at the lambdoid suture and includes the foramen magnum (“large hole”), through which the spinal cord connects with the brain. • The irregularly shaped ethmoid bone forms part of the nasal septum and includes the crista galli, (“cock’s comb”), a superior projection to which the outer covering of the brain attaches. The ethmoid bone is surrounded by the cribriform plate, a porous region through which the olfactory (smell) nerves pass. The bone also includes the superior and middle nasal conchae, projections that increase the turbulence of airflow through the nasal passages. • The sphenoid bone is butterfly shaped and centrally located within the skull. The sphenoid bone supports part of the base of the brain, forms part of the orbits of the eyes, and is connected to all of the other bones of the skull. It includes a small cavity called the sella turcica, (“Turk’s saddle”), which encases the pituitary gland. The foramen ovale is a large opening in the sella turcica through which the trigeminal nerve passes. Other openings in the sphenoid bone include the optic canal, a passageway for the optic nerve, and the superior orbital fissure, through which cranial nerves III, IV, and V, which control eye movements, pass. The central portion of the sphenoid bone is filled with small cavities known as the sphenoid sinuses (Figure 5.12). The temporal bones include the following important features: • zygomatic process—a raised ridge that joins to the zygomatic bone (cheek bone) • styloid process—a thin, needle-like projection that serves as an attachment site for several neck muscles • mastoid process—a neck muscle attachment site that includes cavities known as the mastoid sinuses • external acoustic meatus—a canal that includes the eardrum and connects to the middle ear • jugular foramen—a passageway for the jugular vein, the largest vein leading from the brain • internal acoustic meatus—an opening for the facial and vestibulocochlear nerves Ethmoid sinus Sphenoid sinus Maxillary sinus Frontal sinus © Body Scientifi c International Figure 5.12 The sinuses of the skull.