5. Zygomatic process of frontal bone; 6. Zygomatic bone; 7. Parietal bone; 8. Zygomatic process of temporal bone; 9. Lacrimal foramen; 10. Infraorbital foramen. (d) Ventral aspect of the skull: 1. Incisive bone; 2. Palatine process of the maxilla; 3. Major palatine foramen; 4. Vomer bone; 5. Pterygoid bone; 6. Frontal bone; 7. Palatine bone; 8. Temporal process of the zygomatic bone; 9. Zygomatic process of the temporal bone; 10. Retroarticular process; 11. Mandibular fossa of the articular surface of the temporomandibular joint.
Source: Images reprinted with permission of Morton Publishing Company.
1.13.2 Facium
The facial part of the skull, which encloses the nasal and oral cavities, is divided into oral, nasal, and orbital regions. The oral region surrounding the oral cavity is composed of the incisive, maxillary, palatine, and mandibular bones.
The region surrounding the nasal cavity is composed of the nasal, maxillary, palatine, and incisive bones. The orbital region is formed by the frontal, lacrimal, palatine, sphenoid, and zygomatic bones surrounding the orbit (Figure 1.12c,d).
1.13.3 Maxillae and Mandibles
Normal cats have two maxillas (or maxillae) and two mandibles. The adjective maxillary is often used in a wider sense, e.g. “maxillary fractures,” to include other facial bones, in addition to the maxillary bone itself.
1.14 Maxillary Region
The maxillary bones (maxillae) form the lateral parts of the face and the part of the hard palate that houses the canines and upper cheek teeth. The maxilla articulates with the incisive bone rostrally, the nasal bone dorsally, the vomer bone medially, and the lacrimal and zygomatic bones caudally (Figure 1.13a,b). The maxillae extend to the caudal border of the hard palate laterally and are joined medially by the paired palatine bones to complete the hard palate. The infraorbital canal is located apical to both the maxillary third and fourth premolars below the orbit.
The palatine bone forms the bony part of the hard palate together with the maxillary and incisive bones. The incisive bone located rostrally houses the upper incisors and forms approximately one‐sixth of the hard palate. A pair of openings, the palatine fissures, allows passage of the incisive ducts to the vomeronasal organ. The incisive papilla located just caudal to the maxillary first incisor teeth houses these incisive ducts as they open into the oral cavity The ducts serve as a pathway for air to be drawn in, which is then directed over extensions of the vomeronasal apparatus in the floor of the nasal cavity immediately behind the palatine fissures (Figure 1.14a,b).
The hard palate separates the oral and nasal cavities. The primary palate is the incisive portion of the palate and associated soft tissues. The secondary palate includes the remaining hard and soft palatal structures. Firmly attached, heavily keratinized mucosa covers the hard palate. Seven to eight transverse ridges called rugae protrude from the mucosa with rows of papillae between the ridges. The soft palate begins caudal to the maxillary first molar teeth and separates the nasopharynx dorsally from the oropharynx ventrally.
Figure 1.13 (a) Lateral aspect of right maxilla: 1. Alveolar process; 2. Frontal process; 3. Infraorbital canal; 4. Zygomatic process. (b) Medial aspect of the right maxilla: 1. Maxillotubinates; 2. Palatine process.
The infraorbital canal is located apical to the maxillary third and fourth premolars below the orbit. Compared to the dog, the cat's infraorbital canal is shorter and usually less than five millimeters in diameter.
Figure 1.14 (a) Palatine fissures. (b) Incisive papilla.
1.15 Mandibles
The large bones articulating with the skull that support the lower teeth are the mandibles. Each mandible is composed of a horizontal body and a vertical ramus. The body supports the lower teeth. The ramus has three processes: coronoid, condylar, and angular. The condylar process articulates with the cranium in the temporomandibular joint (TMJ) (Figure 1.15a–c).
The mandibles are connected to each other by a strong fibrocartilaginous joint at the mandibular symphysis. The nerves and vascular supply to the mandibular teeth enter the mandibular canal ventrally on the lingual aspect of the angle of the mandible and course rostrally exiting at the caudal, middle, and rostral mental foramina to supply the rostral mandible, chin, lip, buccal gingiva, and mucosa (Figure 1.16a–c). The tongue and some of the muscles of the hyoid apparatus occupy the intermandibular space.
1.16 Temporomandibular Joint
The head of the condylar process of the mandibular ramus articulates with the base of the zygomatic process of the squamous part of the temporal bone (mandibular fossa) at the TMJ: a transversely elongated (cigar‐shaped) synovial joint (Figure 1.17). The retroarticular process is a caudoventral extension of the mandibular fossa which helps prevent caudal luxation of the mandible (Figure 1.18).
Figure 1.15 (a) Lower jaw. (b) Right mandible buccal aspect: 1. Mandibular body; 2. Mandibular ramus; 3. Masseteric fossa; 4. Coronoid process; 5. Condylar process; 6. Angular process; 7. Middle mental foramen; 8. Caudal mental foramen. (c) Right mandible lingual aspect: 1. Mandibular symphysis articular surface; 2. Mandibular foramen.
The articular cartilage of the TMJ is fibrocartilaginous tissue, with a fibrocartilaginous disc separating the joint into two non‐communicating compartments.
The insertion of the masseter muscle reaches the ventral and rostral aspect of the joint capsule. There is a thin, cartilaginous intra‐articular disc dividing the joint into dorsal and ventral compartments. This disc reduces friction by providing a double synovial film.
