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This is the free full text of AppSurgeOn - 3D Skull Atlas.

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Maxillary Bone

The maxillary bone is the second bone of the splanchnocranium in size. It forms part of the floor of the orbit and of the floor and lateral wall of the nasal cavity. It also contributes to defining infratemporal and pterygopalatine fossae, constituting the anterior border of the inferior orbital and pterygomaxillary fissures. Each maxilla has a body, which is approximately pyramidal, and has anterior, infratemporal (posterior), orbital, and nasal surfaces that enclose the maxillary sinus. Four processes, namely the zygomatic, frontal, alveolar, and palatine processes, arise from the maxillary body. It articulates with the frontal, ethmoid, palatine, nasal, lacrimal, zygomatic, vomer, inferior concha, and contralateral maxillary bones.

  

  

Parts

 

Anterior surface

It is more prominent inferiorly where it overlies the roots of the teeth as alveolar process. The incisive fossa is present superior to the incisor teeth, and the canine fossa lateral to it, being separated by the canine eminence. The infraorbital foramen can be located below the infraorbital margin. The medial border of the surface presents the nasal notch and half of the anterior nasal spine.

 

Infratemporal surface

It constitutes the concave anterior surface of the infratemporal fossa. It is separated from the anterior surface by the zygomatic process and the zygomatico-maxillary ridge (or jugal crest). It presents two or three alveolar canals and the maxillary tuberosity. It also constitutes the anterior boundary of the pterygopalatine fossa, furrowed by the groove for the maxillary nerve.

 

Nasal surface

It constitutes part of the inferior nasal meatus inferiorly and displays the maxillary hiatus superiorly, which allows the maxillary sinus to drain into the middle nasal meatus. Part of the superior border of the hiatus completes some of the ethmoidal air cells. The pyramid shaped maxillary sinus is the biggest of the paranasal sinuses.

Maxillary Sinus

Its floor is related to the dental roots, and bone dehiscences are not rare. The roof of the sinus contains the infraorbital canal, which also may present bone defects. The lateral apex of the sinus extends into the zygomatic process. The walls of the sinus may present ridges anteriorly or posteriorly according to the protrusion of either the canalis sinuosus or the posterior alveolar canals, respectively. Incomplete or complete septa can be present inside the sinus. The maxillary sinus is the first to begin its development. It extends lateral to the infraorbital canal at approximately 4 years of age.

The posterior part of the nasal surface is rough, where it articulates with the perpendicular plate of the palatine bone, and shows a groove that completes the greater palatine canal. The anterior part is marked by the nasolacrimal groove and, more anteriorly, by the conchal crest.

 

Orbital surface

It is triangular, smooth, and forms most of the floor of the orbit. It also forms the anterior edge of the inferior orbital fissure. The anterior border of the orbital surface constitutes part of the infraorbital margin, and it is continuous with the lacrimal crest of the frontal process of the maxillary bone. The lacrimal notch is present on the anteromedial aspect of the surface, where the depression indicating the origin of the inferior oblique muscle may also be visible. The infraorbital groove furrows the posterior border and continues as the infraorbital canal. The canalis sinuosus is also present within the orbital surface and continues into the anterior surface, reaching the nasal cavity.

 

Alveolar process

It is thick, arched, and located below the maxillary sinuses. It surrounds the palatine process anteriorly and laterally. It displays the buccal and the palatal plates, as well as interdental and inter-radicular septa.

 

Frontal process

It is directed posterosuperiorly and presents the anterior lacrimal crest on its lateral surface. The lacrimal tubercle is present at the junction with the orbital surface. A grooves behind the lacrimal crest completes the corresponding one on the lacrimal bone to form the lacrimal sac fossa. The medial surface is part of the lateral nasal wall and presents the ethmoidal crest. Its subapical part, superior to the ethmoidal crest, may complete some of the ethmoidal air cells. The agger nasi is located anterior to the ethmoidal crest.

 

Palatine process

It is thick, horizontal, and extends medially to join the contralateral palatine process with a raised medial border, which constitutes the so called nasal crest for the articulation with the vomer bone, to form the floor of the nasal cavities and the mouth roof. The palate is arched in the anteroposterior and the transverse directions, with a concave inferior surface, which shows depressions for palatine glands, vascular foramina, the grooves for the greater palatine neurovascular bundles, and the median incisive foramen.

Incisive foramen

It is formed by two notches on the two maxillary bones, whose lateral walls are pierced by the lateral incisive foramina. These foramina communicates with the nasal cavities through the incisive canals.

The inferior surface displays the incisive suture and the median palatine suture, which is usually flat, although it may arise as palatine torus. The superior surface has a raised medial edge, called the nasal crest, forming a groove, together with the contralateral one, to house the inferior border of the vomer bone. The higher anterior end of the nasal crest is called the incisor crest and joins the contralateral one to from the anterior nasal spine.

 

Zygomatic process

It is a pyramidal process at the convergence of the infratemporal and the orbital surfaces. It is concave posteriorly, being in continuity with the infratemporal surface. The superolateral surface is rough, due to the articulation with the zygomatic bone. Inferiorly, the zygomatico-maxillary ridge separates the facial and the infratemporal surfaces.

 

Articulations

The maxillary bone articulates with the frontal, ethmoid, palatine, nasal, lacrimal, zygomatic, vomer, inferior concha, and contralateral maxillary bones.

 

Skeletal Landmarks

The medial border and part of the inferior border of the orbit are constituted of the maxillary bone. The infraorbital foramen can be palpated 0.5-1 cm inferior to the infraorbital margin, approximately in the same vertical plane to the supraorbital and the mental foramina. 

 

Anatomical Details

Agger Nasi

The protuberance located anterior to the insertion of the middle nasal concha on the lateral nasal wall, at the base of the ethmoidal crest.

 

Alveolar Canals

Two or three canals visible on the infratemporal surface of the maxillary bone. They transmit the posterior superior alveolar vessels and nerves.

 

Alveolar Process

The inferior part of the maxillary bone, located below the maxillary sinuses and enclosing the palatine process. It contains the alveoli for the superior teeth.

 

Alveolus

Cavity in the alveolar process that houses a tooth. 16 alveoli for the superior teeth are present in total.

 

Anterior Lacrimal Crest

Vertical ridge that divides the lateral surface of the frontal process of the maxillary bone. It continues inferiorly into the infraorbital margin and gives attachment to the medial palpebral ligament.

 

Anterior Nasal Spine

Pointed process at the inferior end of the nasal notch. It articulates with the contralateral one forming the inferior edge of the pyriform aperture.

 

Buccal Plate

Thin lamella of bone that constitutes the wall of the alveoli towards the vestibule of the mouth.

 

Canalis Sinuosus Opening

The opening of the canalis sinuosus, which opens anterior to the incisive canal, near the nasal septum. This canal descends in the orbital floor lateral to the infraorbital canal and passes below the infraorbital foramen, after a medial turn inside the anterior wall of the maxillary sinus. Then, it reaches the anterior end of the inferior concha and follows the pyriform aperture until its exit point. This canal houses the anterior superior alveolar nerve and vessels.

 

Canine Eminence

Rounded eminence that corresponds to the alveolus of the canine tooth. It separates the incisive and canine fossae.

 

Canine Fossa

Fossa above the alveoli posterior to the canine eminence.

 

Conchal Crest

Posterosuperiorly inclined ridge for the articulation with the inferior nasal concha.

 

Ethmoidal Crest

Oblique crest located below the areas that complete the walls of ethmoidal air spaces. It articulates posteriorly with the middle nasal concha, contributing to form the axilla (i.e. curved insertion on the lateral nasal wall) of the middle turbinate.

 

Frontal Process

The process arising superiorly from the body of the mandible to articulate with the frontal bone and constitute part of the medial orbital wall and of the pyriform aperture.

 

Greater Palatine Groove

The groove posterior to the maxillary hiatus on the nasal surface. It descends antero-inferiorly from the midpoint of the posterior border of the maxillary bone. The perpendicular plate of the palatine bone completes it to form the greater palatine canal.

 

Incisive Canal

The canal lying near the median margin of the anterior part of the superior surface of the palatine process, connecting the nasal cavity and the mouth. This canal bears terminal branches of the greater palatine vessels and the nasopalatine nerve.

 

Incisive Foramen

The incisive foramen is formed by the apposition of two notches on the medial surface of the palatine processes. It lies behind the medial incisor teeth on the inferior surface.

 

Incisive Fossa

Fossa above the alveoli of the incisors, anterior to the canine eminence.

 

Incisive Notch

The notch located behind the medial incisor teeth on the inferior surface of the palatine process. It joins the contralateral one to form the incisive foramen.

 

Incisive Suture

The fused suture, more faint in elder skulls, extending from the incisive foramen to the interdental space between the lateral incisor and the canine teeth.

 

Incisor Crest

Thin ridge projecting superiorly from the raised medial border of the palatine process. It is the posterior prolongation of the nasal spine.

 

Infraorbital Canal

The anterior continuation of the infraorbital groove inside the roof and the anterior wall of the maxillary sinus. It opens on the anterior surface below the infraorbital margin transmitting the infraorbital neurovascular bundle.

 

Infraorbital Foramen

The foramen lying above the canine fossa as the opening of the infraorbital canal.

 

Infraorbital Groove

The impression of the infraorbital neuromuscular bundle on the orbital surface of the maxillary bone.

 

Infraorbital Margin

The anterior edge of the floor of the orbit, between the orbital and the anterior surfaces of the maxillary bone. It continues on the frontal process as the anterior lacrimal crest.

 

Inter-dental Septum

Lamella of bone that separates two alveoli, connecting the buccal and the palatal plates.

 

Inter-radicular Septum

Lamella of bone that separates the roots of the tooth in each alveolus. The number of septa in each alveolus changes according to the number of roots of its tooth. The incisive, canine and second premolar teeth usually have one root, the first premolars show two roots, and the molars usually three roots.

 

Lacrimal Notch

The impression for the nasolacrimal duct in the anteromedial angle of the orbital surface.

 

Lacrimal Sac Groove

Vertical groove behind the lacrimal crest that is completed by a groove on the lacrimal bone to complete the lacrimal sac fossa.

 

Lacrimal Tubercle

A small tubercle arising at the junction between the anterior lacrimal crest and the orbital surface. It can be used as a guide to the lacrimal sac.

 

Lateral Incisive Foramen

The foramen in the lateral walls of the incisive fossa through which the incisive canal reaches the mouth cavity. Sometimes anterior and posterior median incisive foramina are present, the anterior being traversed by the left nasopalatine nerve, while the posterior by the right one.

 

Maxillary Hiatus

Irregular opening that gives access to the maxillary sinus. Parts of the upper border of the hiatus complete air spaces owing to the articulations with ethmoid and lacrimal bones.

 

Maxillary Nerve Groove

Groove located on the posterolateral surface of the maxillary bone, which constitutes the smooth anterior boundary of the pterygopalatine fossa, above the maxillary tuberosity. It is the impression of the maxillary nerve on the bone.

 

Maxillary Tuberosity

A rounded eminence, that is present on the posteroinferior aspect of the body of the maxillary bone. It is rough on its lateral side where it articulates with the pyramidal process of the palatine bone.

 

Nasal Notch

The concave shaped medial edge of the anterior surface of the maxillary bone. It forms the lateral and half of the inferior borders of the pyriform aperture.

 

Naso-lacrimal Groove

The groove anterior to the maxillary hiatus that continues superiorly with the lacrimal sac groove and accounts for about 2/3 of the circumference of the nasolacrimal canal. The descending part of the lacrimal bone and the lacrimal process of the inferior nasal concha complete the rest of the canal; which allows the nasolacrimal duct to open into the inferior meatus.

 

Palatal Plate

Thin lamella of bone that constitutes the wall of the alveoli towards the palatine process of the maxillary bone.

 

Palatine Gland Depression

Depressions and foramina for the palatine glands marks the inferior surface of the palatine process.

 

Palatine Grooves

Sulci on the inferior surface of the palatine process housing branches of the greater palatine neurovascular bundle, and constituting the anterior extension of those present on the palatine bone.

 

Palatine Process

The part of the maxillary bone that extends medially and joins the contralateral one to form the floor of the nasal cavities and the mouth roof. It has a raised medial border, which constitutes the nasal crest for the articulation with the vomer bone.

 

Zygomatico-Maxillary Ridge

The crest that ascends from the alveolus of the first molar tooth to the zygomatic process and contributes to the separation between the anterior and the infratemporal surfaces. Synonym: Jugal crest.

 

Zygomatic Process

The process that projects laterally from the body of the maxillary bone to articulate with the zygomatic bone.

 

References

Anatomy of the Human Body. Gray, H. Philadelphia: Lea & Febiger, 1918; Bartleby.com, 2000

Rhoton's Cranial Anatomy and Surgical Approaches. Rhoton AL. Lippincott Williams & Wil-kins; 2007

Paranasal sinuses: anatomic terminology and nomenclature. Stammberger HR, Kennedy DW, Anatomic Terminology G. Ann Otol Rhinol Laryngol Suppl 167:7-16, 1995 

Maxillary sinus anatomy: a cadaveric study with clinical implications. Gosau M, Rink D, Driemel O, Draenert FG, Anat Rec (Hoboken) 292:352-354, 2009 

 

Authors

 

Francesco Belotti, MD

Neurosurgery Resident
University of Brescia (Italy) 
"Spedali Civili" Hospital Brescia (Italy)
Scientific Team - UpSurgeOn

 

Federico Nicolosi, MD

Neurosurgeon
University of Milan
"Spedali Civili" Hospital Brescia (Italy)
Scientific Team - UpSurgeOn