As with vertebrates, muscles must cross a joint inside the exoskeleton. This skeleton type provides defence against predators, supports the body, and allows for movement through the contraction of attached muscles. For example, the shells of crabs and insects are exoskeletons ( Figure 19.3). You can also clearly see the mental foramen in the mandible.An exoskeleton is an external skeleton that consists of a hard encasement on the surface of an organism. The alveolar processes are the areas in the maxillae and the mandible that form the sockets for the teeth. The depressions in the maxillae, just above the canines, are the canine fossae. The canine eminence is the ridge of bone over the maxillary canine. Below the orbit, in the maxillae, are the infraorbital foramina, which transmit the infraorbital vessels and nerves to the upper lip, lower eyelid, and side of the nose you can also see the intermaxillary suture. 26-5, you can also see the nasal or piriform aperture. A few sutures, such as the coronal, have special names, but most of them are named by the two bones they join. Toward either side at the top, you can see a part of the coronal suture, also called the frontoparietal suture. The nerve and blood supply to the forehead come through this opening. The supraorbital notch or foramen is seen in the upper rim of the orbit in the frontal bone. 26-5, you can again see that the rim of the orbit is formed by the frontal, zygomatic, and maxillary bones. From this view, portions of the zygomatic bones, the temporal bones, and just a tiny portion of the posterior part of the parietal bones can also be seen. This is a major area of endochondral bone formation, which is an important factor in the development of facial profiles and types of malocclusions. 26-3 is known as the sphenoccipital synchondrosis. The area marked by the dashed line in Fig. It is difficult to see the suture line between the sphenoid and the occipital bones because it disappears when a person is about 18 years of age. Just behind that and running the full width of the skull is the sphenoid bone, which is discussed in greater detail later in this chapter. Just behind and above the palate, a small portion of the vomer bone can be seen, forming the lower part of the nasal septum. 26-3, the hard palate, which is formed by the palatal processes of the maxillae and the palatal processes of the palatine bones, is visible. Nevertheless, in the anterior region illustrated in Fig. There are numerous points or landmarks of study, and it is difficult to see the suture lines between the bones in many instances. The most difficult view of the skull for the beginning student of anatomy is the inferior view. The following eight bones make up the neurocranium, the bones surrounding the brain: They are grouped into two categories: one group surrounds the brain, and one group forms the face. Some of these are single, and some are paired bones. However, the discussion is certainly not all inclusive.Įxcluding the three small ossicles (the malleus, incus, and stapes in each ear, which aid in hearing), the skull is composed of 22 bones. This chapter presents the more important bones of the skull and their landmarks. They surround the brain and protect it from injury, form the facial skeleton, and participate in the growth process of the jaws, which in turn controls whether a patient has a malocclusion (improper relationship of the teeth and jaws) and whether there is balance between the mid face and lower face. The bones of the skull play several different roles. To describe where growth takes place in the maxillae and mandible to allow for increase in arch length.To describe in detail the various parts and landmarks of the mandible.To describe in detail the various parts and landmarks of the maxillae.To describe the pterygoid processes of the sphenoid bone and their components.To describe the boundaries of the three cranial fossae and what lies within them.To name the openings, foramina, and canals as seen from the aforementioned views.To identify the various bones and sutures as seen from anterior, lateral, posterior, inferior, and interior views of the skull. To name the bones of the neurocranium and viscerocranium.
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