136 Anatomy & Physiology Essentials Copyright Goodheart-Willcox Co., Inc. • 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. SELF CHECK 1. Scientists often divide the human skeleton into two parts. What are these parts called? 2. Which bones make up the axial skeleton? 3. What holds the bones of the skull together? Is movement possible at these joints? Why is this important? 4. List the two functions of the fontanels in a baby’s skull. 5. List the eight cranial bones and tell where each is found. 6. List the fourteen facial bones and tell where each is found. Vertebral Column Although the word spine suggests a straight, rigid bar, the human spine, or vertebral column, is anything but straight and rigid. The human spinal column is well designed to perform its functions of protecting the extremely delicate spinal cord, while supporting the weight of the trunk and allowing flexibility in multiple directions. Thirty-three stacked, individual bones called vertebrae comprise the spine. The vertebrae differ in size and shape in the different regions of the spine to best fulfill their respective functions (Figure 5.13). 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 • 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. Ethmoid sinus Sphenoid sinus Maxillary sinus Frontal sinus © Body Scientific International Figure 5.12 The sinuses of the skull.