FACIAL BONES IN DOMESTIC ANIMALS NASAL BONES • Horse • The posterior ends of two bones together form a notch into which the pointed anterior ends of the two frontals are received and excavated to form part of the frontal sinus. • The anterior end is pointed. • Dog • It is long and wider in front than behind. • The dorsal face is concave in its length and forms a central groove with its fellow. • The medial borders project into the nasal cavity to form the internal nasal crest. • The posterior ends resemble those of the ox. • The anterior ends form a semicircular notch • Fowl • It is small thin plate with a body and three processes-frontal, premaxillary and maxillary. • These circumscribe the anterior nares with the premaxilla and the maxilla. PREMAXILLA BONE • Horse • The bodies of the two bones are fused together. • The body of each bone is thicker and presents three alveoli for the upper incisors. • The medial surface is rough and joins the opposite bone; it presents a groove, which with a similar one of its fellow forms the foramen incisivum. • The nasal process is longer and presents at its junction with the maxillary bone an alveolus for the canine tooth. • The palatine process is wide and the palatine fissure narrow. • Dog • The body presents three alveoli for the incisors and with the maxillary bone forms an alveolus for the canine tooth. • Foramen incisivum is very small. • The palatine fissure is short but wide. PREMAXILLA BONE • Fowl • The premaxilla forms the skeleton of the upper portion of the beak and fuse to form a solid bone before hatching. • They form the anterior boundary of the external opening of the nasal cavity. • They present three pairs of processes-the palatine process which meets the palatine, the maxillary processes which extend backward and meet the maxilla and the nasal processes which extends dorsally and backward along the median line and between the nasal bones and meet the frontals. MAXILLA BONE • Horse • The facial crest is prominent. • The infra-orbital foramen is at the level of the third cheek tooth and a small canal from this extends into the pre- maxilla. • The palatine can is formed between the medial face of the body of the maxilla and the vertical part of the palatine bone. • The medial borders of the palatine processes bear nasal crests in their nasal aspect and these form a groove for the vomer. • At the junction of the maxilla and pre-maxilla is an alveolus for the canine tooth. • Dog • The facial crest is absent. • The infra-orbital foramen is as in the horse. MAXILLA BONE • DOG • Frontal process fits into a deep notch between nasal and orbital parts of frontal bone. • Maxillary and alveolar tuberosities are absent, but behind the last alveolus is a pointed pterygoid process. • There is a large alveolus for the canine tooth at the junction with premaxilla. • Fowl • There is slender rod like bones placed on the sides and partly on the floor of the nasal cavity. • The two palatine processes do not meet, but join the palatine and vomer posteriorly. • The maxilla joins the pre-maxilla and nasal anteriorly while it is continuous with malar posteriorly. PALATINE BONE • Horse • The horizontal part is narrow and is not excavated to form the palatine sinus. • Anterior palatine foramen is formed between the anterior border of the horizontal part and the palatine process of the maxilla. • The palatine canal is formed between the maxilla and the vertical part. • The perpendicular part is more extensive consists of two plates and is excavated to form the palatine part of the spheno-palatine sinus, behind the spheno palatine foramen. • The inner plate curves medially to articulate with the vomer. • The outer plate joins the maxilla frontal and the orbital wing of the sphenoid. It may join the lacrimal also. • Dog • The horizontal part is extensive and forms the posterior one third of the bony palate. • The palatine canal is sometimes formed entirely in the horizontal part. • The perpendicular part is very extensive. PALATINE BONE • DOG • Its lateral surface is free and forms most of the medial wall of the pterygo-palatine fossa. • The maxillary foramen is situated in deep recess between this bone and the zygomatic process of the malar. Just above this is another foramen opening into the nasal cavity. • The posterior palatine and spheno-palatine foramina are situated further back and a little lower. • The former is ventral to the latter. A horizontal plate extends from the nasal surface, meets its fellow and the laminae of the vomer to complete the lamina transversalis that divides the olfactory and the respiratory parts of the nasal cavity. • There is no palatine sinus. • Fowl • It is wide behind and narrow in front. It forms lateral boundary of the posterior opening of the al cavity and part of the roof of mouth. • It meets the pterygoid and the sphenoid posteriorly and the premaxilla and maxilla anteriorly. PTERYGOID BONE • Horse • Shorter and narrower. • The lateral surface articulates with the palatine, vomer and sphenoid, concurring with last in the formation of the pterygoid canal. • Dog • It is wide quadrilateral and short. • Fowl • It is rod shaped and extends between the rostrum of the sphenoid medially and quadrate bone laterally. LACRIMAL BONE • Horse • It is smaller. • The facial part is less extensive and presents a small lacrimal tubercle about an inch from the orbital margin. • Lacrimal bulla is absent. • Dog • It is very small. • Orbital face is small triangular and has lacrimal canal. • The facial part does not extend beyond the orbital margin. • Fowl • It is triangular plate of bone situated at the anterior margin of the orbit. Its medial edge meets the frontal. • The apex, pointed downward, is continued by a long curved process. MALAR BONE • Horse • The facial surface is very small. • The posterior extremity is not divided and is overlapped by the zygomatic process of the squamous temporal. • Dog • The body consists of a dorsal lacrimal process and ventral maxillary process. • The facial part is small and convex. • The zygomatic process forms the bulk of the bone. • The dorsal border of this process is free anteriorly and forms part of the orbital rim and behind it meets the zygomatic process of the temporal. • It bears an eminence-frontal process for the attachment of the orbital ligament. • Fowl • It is a slender rod of bone extending from the maxilla anteriorly and to the quadrate posteriorly. • The anterior part of the bone is called the jugal and posterior part the quadrato-jugal bone. TURBINATE BONE • Horse • The dorsal turbinate is longer and larger. • Each turbinate has an anterior coiled part and posterior curved portion. • The coiled parts of the two bones are rolled towards the septum and each other. • Dog • The turbinates are richly convoluted. However, the anterior part of the dorsal bone form a simple curved plate overhang the ventral bone. • The posterior part of the dorsal bone is not clearly separated from the lateral mass of ethmoid. The ventral bone is as in the ox; but has additional tertiary lamellae. • Fowl • They are three in number-anterior, middle and posterior. • The middle is the largest. • The posterior is the smallest. VOMER BONE • Horse • The ventral border is attached to the nasal crests of the maxillae and so the posterior nares are completely separated in the skull. • Dog • Posteriorly it is not in contact with the floor of the nasal cavity and does not divide completely the posterior nares. • Near the posterior nares the two plates of vomer curve outward and join the lamina lateralis of ethmoid and the palatine bones to form the lamina transversalis. • Fowl • It is a slender rod extending forward from the rostrum of the sphenoid and is part of the nasal septum and is attached above to the septal cartilage in its anterior part. NASAL CAVITY • Horse • The nasal cavity and the posterior nares are completely divided, as the vomer meets the nasal crests of the palatine and maxilla. • Dog • The nasal cavity conforms to the shape of the face. • The turbinates occupy the cavities to a large extent. • The posterior part of the cavity is divided by the lamina transversalis into an upper olfactory region and a lower naso pharyngeal meatus. • The posterior nares are undivided. MANDIBLE • Horse • The two halves of the mandible fuse completely. • The alveolar border of the body presents six alveoli for the lower incisors and two for the canines. • The lingual groove is absent. • The anterio-medal part of the condyle presents a depression. • The fovea pterygoidea is for the lateral pterygoid muscle. • Coronoid process is less prominent. • The rami diverge less than in ox. • Dog • The two halves do not fuse. • The alveolar border of the body presents six alveoli for the incisors and two for canines. • The horizontal part of ramus carries seven alveoli for the lower cheek teeth. • The interalveolar space is very short or even absent. • There are two or three mental foramina on either side. • The vertical part is relatively small. • The lateral face of the vertical part presents a deep masseteric fossa. MANDIBLE • DOG • The posterior border bears an angular process at the level of the mandibular foramen. • This is the equivalent of the angle of other animals. The condyle is placed very low. • The coronoid process is extensive and is bent slightly outwards and backward. • Fowl • It is a single bone and each half is made up of five pieces in the embryo. • The two halves fuse anteriorly. Posteriorly its articular part carries an articular area for the lower end of the quadrate bone. Behind this, the ventral border is carried upward and backward by a process.