Os Zygomaticum, Os Nasale, Os Lacrimale, Os Palatine, Corpus Maxillae (PDF)

## Os zygomaticum - Kindbenet, os zygomaticum, has three surfaces. They face forward and laterally, towards the eye socket, and towards the temporal region. - It has one process, which forms the zygomatic arch with the temporal bone. ## Os nasale - The nasal bone, os nasale, is a small square b...

## Os zygomaticum - Kindbenet, os zygomaticum, has three surfaces. They face forward and laterally, towards the eye socket, and towards the temporal region. - It has one process, which forms the zygomatic arch with the temporal bone. ## Os nasale - The nasal bone, os nasale, is a small square bone. It forms part of the external nasal skeleton. - Three of its edges are part of sutures. The lowermost edge is free in a skull without soft tissue. - The nasal bones meet at the midline. - The nasal bone connects to the forehead bone and posteriorly with the superior projection of the maxilla. ## Os lacrimale - The lacrimal bone, os lacrimale, is a small square bone. - It has a groove or depression on its lateral surface. This forms part of the lacrimal sac fossa. ## Os palatinum - The palatine bone, os palatinum, consists of two bony plates which meet at a right angle. - One plate is horizontal, the other is vertical. - These plates are square-shaped, and the horizontal one is the smallest. - On the upper part of the vertical plate two small processes can be seen, separated by an indentation. - The indentation contributes to forming the sphenopalatine foramen. - The horizontal plate of the palatine bone forms the posterior quarter of the hard palate. The greater palatine foramen and the lesser palatine foramina can be found here. ## Corpus maxillae - The upper surface, *facies orbitalis*, is part of the eye socket. It is separated from the anterior surface by a sharp ridge. - The upper surface is separated from the posterior surface by an unnamed ridge. The ridge between the upper and posterior surface contributes to the inferior orbital fissure. - On the upper surface of the body of the maxilla, the infraorbital groove can be seen. - The groove continues into the infraorbital canal, which ends at the infraobital foramen. - The posterior surface, *facies infratemporalis*, faces the infratemporal fossa and the pterygopalatine fossa. On the surface are the alveolar foramina. - These carry blood vessels and nerves to the posterior teeth. - The foramina of the infratemporal fossa lie on the lateral and larger part of the surface. - The medial and smaller part of the surface faces the pterygopalatine fossa. - The lowermost part of the *facies infratemporalis* is not free, but forms a suture with the pterygoid process of the sphenoid bone. - The suture (between the maxilla and the pterygoid process) can be found further down on the posterior surface of the maxilla. - This means that the pterygoid process is in close proximity to the wisdom teeth. - This is particularly important for the hamulus pterygoideus, which can be seen as a point on the image. - It can be palpated from the mouth behind and medial to the last molar. - The anterior surface, *facies nasalis*, forms the base of the pyramid that is the nasal cavity. - It is normally covered by the nasal conchae. When these are removed, the large opening of the maxillary sinus can be seen. - The maxillary sinus fills most of the body of the maxilla. - The walls of the maxillary sinus corresponds to the surfaces of the body of the maxilla. - The opening of the maxillary sinus is very large. When other skull bones are added, the opening becomes much smaller. - When the mucous membrane is added, the opening becomes like a slit. - The maxillary sinus almost completely fills the body of the maxilla, making it somewhat pyramid-shaped. When describing the walls of the sinus, it should be done from "inside," as if the observer were inside the sinus. - A concavity on an outer surface of the maxilla is formed as a convexity on the wall of the maxilla. - For example, the canine fossa on the anterior surface corresponds to a convexity on the anterior wall of the maxillary sinus. - The posterior surface of the maxilla is convex. The posterior wall of the maxillary sinus is concave. - This is similar to describing an eggshell. The description will vary depending on whether you view the outside of the shell, which is convex, or the inside of the shell, which is concave.