Chapter 26
5b. The Facial Bones. 1. The Nasal Bones. Ossifakiae and Ossinessalia.
The Nasal Bones are two small oblong bones varying in size and form in different individuals. They are placed side by side at the middle and upper part of the face and form by their junction the bridge of the nose. Each has two surfaces and four borders. Surfaces.
The outer surface is concave or convex from above downward, convex from side to side. It is covered by the Procurest and Compressor Naris and perforated about its centre by a common, for the transmission of a small vein. The inner surface is concave from side to side and is traversed from above downward by a groove for the passage of a branch of the Nasociliary Nerve.
Borders. The superior border is narrow, thick and serrated for articulation with the nasal notch of the frontal bone. The inferior border is thin and gives attachment to the lateral cartilage of the nose. To its middle is a notch which marks the end of the groove just referred to.
The lateral border is serrated, beveled at the expense of the inner surface above and of the outer below to articulate with the frontal process of the maxilla. The medial border, thicker above than below, articulates with its fellow of the opposite side and is prolonged behind into a vertical crest which forms part of the nasal septum. This crest articulates from above downward with the spine of the frontal, the perpendicular
plane of the ethmoid and the septal cartilage of the nose. Ossification. Each bone is ossified from one centre which appears at the beginning of the third month of fetal life in the membrane overlying the front part of the cartilaginous nasal capsule. Articulations.
The nasal articulates with four bones, two of the cranium, the frontal and ethmoid and two of the face, the opposite nasal and the maxilla. 5b2. The maxillae, upper jaw. The maxillae are the largest bones of the face excepting the mandible and form by their
union the whole of the upper jaw. Each assists in forming the boundaries of three cavities, vis, the roof of the mouth, the floor and lateral wall of the nose and the floor of the orbit. It also enters into the formation of two phossae, the infratemporal and pterygopalatine and two fissures, the inferior orbital and pterygomaxillary.
Each bone consists of a body and four processes, zygomatic, frontal, alveolar and palatine. The body, corpus maxillae. The body is somewhat pyramidal in shape and contains a large cavity, the maxillary sinus, antrum of Haimor. It has four surfaces, an anterior, a posterior or infratemporal, a superior or orbital and
a medial or nasal. Surfaces. The anterior surface is directed forward and lateralward. It presents at its lower part a series of eminences corresponding to the positions of the roots of the teeth.
Just above those of the incisor teeth is a depression, the incisive fossa, which gives The alveolar border below the fossa is attached a slip of the orbicularis oris. Above and a little lateral to it, the nasalis arises. Lateral to the incisive fossa is another depression, the canine fossa. It is larger and deeper than the incisive fossa and is separated from it by a vertical
ridge, the canine eminence, corresponding to the socket of the canine tooth. And the canine fossa gives origin to the caninus. Above the fossa is the infraorbital foramen, the end of the infraorbital canal. It transmits the infraorbital vessels and nerve. Above the foramen is the margin of the orbit, which affords attachment to part of the quadratus
labiae superioris. Medially the anterior surface is limited by a deep concavity, the nasal notch, the margin of which gives attachment to the dilator narrus posterior and ends below in a pointed process, which with its fellow of the opposite side forms the anterior nasal spine. The infratemporal surface is convex, directed backward and lateralward, and forms part of
the infratemporal fossa. It is separated from the anterior surface by the zygomatic process and by a strong ridge, extending upward from the socket of the first molar tooth. It is pierced about its centre by the apertures of the alveolar canals, which transmit the posterior superior alveolar vessels and nerves.
At the lower part of this surface is a rounded eminence, the maxillary tuberosity, especially prominent after the growth of the wisdom tooth. It is rough on the lateral side for articulation with the pyramidal process of the palatine bone and in some cases articulates with the lateral pterygoid plate of the sphenoid. It gives origin to a few fibres of the pterygodeus internus.
Immediately above this is a smooth surface, which forms the anterior boundary of the pterygopalatine fossa and presents a groove for the maxillary nerve. This groove is directed lateralward and slightly upward and is continuous with the infratorbital groove on the orbital surface. The orbital surface is smooth and triangular and forms the greater part of the floor of
the orbit. It is bounded medially by an irregular margin which in front presents a notch, the lacrimal notch. Behind this notch the margin articulates with the lacrimal, the laminar papyrachea of the ethmoid and the orbital process of the palatine.
It is bounded behind by a smooth rounded edge which forms the anterior margin of the inferior orbital fissure and sometimes articulates at its lateral extremity with the orbital surface of the great wing of the sphenoid. It is limited in front by part of the circumference of the orbit, which is continuous medially with the frontal process and laterally with the zygomatic process.
Near the middle of the posterior part of the orbital surface is the infratorbital groove for the passage of the infratorbital vessels and nerve. The groove begins at the middle of the posterior border where it is continuous with that near the upper edge of the infratemporal surface and passing forward ends in a canal which subdivides into two branches.
One of the canals, the infratorbital canal, opens just below the margin of the orbit. The other, which is smaller, runs downward in the substance of the anterior wall of the maxillary sinus and transmits the anterior superior alveolar vessels and nerve to the front teeth of the maxilla. From the back part of the infratorbital canal, a second small canal is sometimes given off.
It runs downward in the lateral wall of the sinus and conveys the middle alveolar nerve to the premolar teeth. At the medial and fore part of the orbital surface, just lateral to the lacrimal groove, is a depression which gives origin to the obliquus oculi inferior. The nasal surface presents a large irregular opening leading into the maxillary sinus.
At the upper border of this aperture are some broken air cells which in the articulated skull are closed in by the ethmoid and lacrimal bones. Below the aperture is a smooth concavity which forms part of the inferior meatus of the nasal cavity and behind it is a rough surface for articulation with the perpendicular part of the palatine bone.
This surface is traversed by a groove commencing near the middle of the posterior border and running obliquely downward and forward. The groove is converted into a canal, the pterigopalatine canal, by the palatine bone. In front of the opening of the sinus is a deep groove, the lacrimal groove, which is converted into the nasal lacrimal canal by the lacrimal bone and inferior nasal concha.
This canal opens into the inferior meatus of the nose and transmits the nasal lacrimal duct. More anteriorly is an oblique ridge, the conchal crest, for articulation with the inferior nasal concha. The shallow concavity above this ridge forms part of the atrium of the middle meatus of
the nose and that below it part of the inferior meatus. The maxillary sinus or atrium of Haimor, sinus maxillaris. The maxillary sinus is a large pyramidal cavity within the body of the maxilla. Its apex, directed lateral wood, is formed by the zygomatic process, its base, directed medial wood, by the lateral wall of the nose.
Its walls are everywhere exceedingly thin and correspond to the nasal orbit, anterior and infratemporal surfaces of the body of the bone. Its nasal wall or base presents, in the disarticulated bone, a large irregular aperture communicating with the nasal cavity. In the articulated skull this aperture is much reduced in size by the following bones.
The onsenate process of the ethmoid bone, the ethmoidal process of the inferior nasal concha below, the vertical part of the palatine behind, and a small part of the lacrimal above and in front. The sinus communicates with the middle meatus of the nose, generally by two small apertures left between the above-mentioned bones.
In the fresh state, usually only one small opening exists, near the upper part of the cavity, the other is closed by mucous membrane. On the posterior wall are the alveolar canals, transmitting the posterior superior alveolar vessels and nerves to the molar teeth. The floor is formed by the alveolar process of the maxilla, and if the sinus be of an
average size, is on a level with the floor of the nose. If the sinus be large it reaches below this level. Projecting into the floor of the antrum are several conical processes, corresponding to the roots of the first and second molar teeth. In some case the floor is perforated by the fangs of the teeth.
The infraorbital canal usually projects into the cavity as a well-marked ridge extending from the roof to the anterior wall. Additional ridges are sometimes seen in the posterior wall of the cavity and are caused by the alveolar canals. The size of the cavity varies in different skulls, and even on the two sides of the same
skull. The zygomatic process. Processus zygomaticus malar process. The zygomatic process is a rough triangular eminence situated at the angle of separation of the anterior, zygomatic and orbital surfaces.
In front it forms part of the anterior surface, behind it is concave and forms part of the infratemporal fossa. Above it is rough and serrated for articulation with the zygomatic bone, while below it presents the prominent arched border which marks the division between the anterior and infratemporal surfaces.
The frontal process. Processus frontalis, nasal process. The frontal process is a strong plate which projects upward, medialwards and backwards, by the side of the nose, forming part of its lateral boundary. Its lateral surface is smooth, continuous with the anterior surface of the body, and
gives attachment to the quadratus labii superioris, the orbicularis oculi and the medial palpebral ligament. Its medial surface forms part of the lateral wall of the nasal cavity. At its upper part is a rough, uneven area, which articulates with the ethmoid, closing in the anterior ethmoidal cells.
Below this is an oblique ridge, the ethmoidal crest, the posterior end of which articulates with the middle nasal concha, while the anterior part is termed the agonasi, the crest forms the upper limit of the atrium of the middle meatus. The upper border articulates with the frontal bone and the anterior with the nasal. The posterior border is thick and hollowed into a groove, which is continuous below with
the lacrimal groove on the nasal surface of the body. By the articulation of the medial margin of the groove with the anterior border of the A corresponding groove on the lacrimal is brought into continuity, and together they form the lacrimal fossa for the lodgement of the lacrimal sac. The lateral margin of the groove is named the anterior lacrimal crest, and continues
below with the orbital margin. At its junction with the orbital surface is a small tubercle, the lacrimal tubercle, which serves as a guide to the position of the lacrimal sac. The alveolar process processes alveolaris. The alveolar process is the thickest and most spongy part of the bone.
It is broader behind than in front, and excavated into deep cavities for the reception of the teeth. These cavities are eight in number and vary in size and depth according to the teeth they contain. That for the canine tooth is the deepest.
Those for the molars are the widest, and are subdivided into minor cavities by septa. Those for the incisors are single, but deep and narrow. The buccinator arises from the outer surface of this process, as far forward as the first molar tooth. When the maxillae are articulated with each other, their alveolar processes together form
the alveolar arch. The centre of the anterior margin of this arch is named the alveolar point. The palatine process processes palatinus, palatal process. The palatine process, thick and strong, is horizontal and projects medial wood from the nasal surface of the bone.
It forms a considerable part of the floor of the nose and the roof of the mouth and is much thicker in front than behind. Its inferior surface is concave, rough and uneven, and forms, with the palatine process of the opposite bone, the anterior three-fourths of the hard plate. It is perforated by numerous foramina for the passage of the nutrient vessels.
Is channeled at the back part of its lateral border by a groove, sometimes a canal, for the transmission of the descending palatine vessels and the anterior palatine nerve from the sphenopalatine ganglion, and presents little depressions for the lodgment of the palatine glands. When the two maxillae are articulated, a funnel-shaped opening, the incisive foramina, is seen in
the middle line, immediately behind the incisor teeth. In this opening, the orifices of two lateral canals are visible. They are named the incisive canals, or foramina of Stenson. Through each of them passes the terminal branch of the descending palatine artery and the nasopalatine nerve.
Occasionally, two additional canals are present in the middle line. They are termed the foramina of Scarpa, and when present, transmit the nasopalatine nerves, the left passing through the anterior and the right through the posterior canal. On the undersurface of the palatine process, a delicate linear suture, well seen in young skulls, may sometimes be noticed extending lateralward and forward on either side from
the incisive foramina to the interval between the lateral incisor and the canine tooth. The small part in front of this suture constitutes the premaxilla, or incisivum, which in most vertebrates forms an independent bone. It includes the whole thickness of the alveolus, the corresponding part of the floor of the nose and the anterior nasal spine, and contains the sockets of the incisor teeth.
The upper surface of the palatine process is concave from side to side, smooth, and forms the greater part of the floor of the nasal cavity. It presents, close to its medial margin, the upper orifice of the incisive canal. The lateral border of the process is incorporated with the rest of the bone. The medial border is thicker in front than behind, and is raised above into a ridge,
the nasal crest, which, with the corresponding ridge of the opposite bone, forms a groove for the reception of the vomer. The front part of this ridge rises to a considerable height and is named the incisor crest. It is prolonged forward into a sharp process, which forms, together with a similar process of the opposite bone, the anterior nasal spine.
The posterior border is serrated for articulation with the horizontal part of the palatine bone. Ossification The maxilla is ossified in membrane. Mole and faucet maintain that it is ossified from two centres only, one for the maxilla proper and one for the premaxilla.
These centres appear during the sixth week of foetal life and unite in the beginning of the third month, but the suture between the two portions persists on the palate until nearly middle life. Mole states that the frontal process is developed from both centres. The maxillary sinus appears as a shallow groove on the nasal surface of the bone about the
fourth month of foetal life, but does not reach its full size until after the second dentition. The maxilla was formerly described as ossifying from six centres. One, the orbiter nasal, forms that part of the body of the bone which lies medial to the infraorbital canal, including the medial part of the floor of the orbit and the lateral
wall of the nasal cavity. A second, the zygomatic, gives origin to the portion which lies lateral to the infraorbital canal, including the zygomatic process. From the third, the palatine, is developed the palatine process posterior to the incisive canal together with the adjoining part of the nasal wall.
A fourth, the premaxillary, forms the incisive bone which carries the incisor teeth and corresponds to the premaxilla of the lower vertebrates. Some anatomists believe that the premaxillary bone is ossified by two centres. A fifth, the nasal, gives rise to the frontal process and the portion above the canine tooth. And a sixth, the infravomorine, lies between the palatine and the premaxillary centres
and beneath the voma. This centre, together with the corresponding centre of the opposite bone, separates the incisive canals from each other. Articulations The maxilla articulates with nine bones, two of the cranium, the frontal and ethmoid, and
seven of the face, vis the nasal, zygomatic, lacrimal, inferior nasal concha, palatine, voma and its fellow of the opposite side. Sometimes it articulates with the orbital surface and sometimes with the lateral pterygoid plate of the sphenoid. Changes produced in the maxilla by age
At birth the transverse and anteroposterior diameters of the bone are each greater than the vertical. The frontal process is well marked and the body of the bone consists of little more than the alveolar process, the teeth sockets reaching almost to the floor of the orbit. The maxillary sinus presents the appearance of a furrow on the lateral wall of the nose.
In the adult the vertical diameter is the greatest, owing to the development of the alveolar process and the increase in size of the sinus. In old age the bone reverts in some measure to the infantile condition, its height is diminished and after the loss of the teeth the alveolar process is absorbed and the lower part of the bone contracted and reduced in thickness.
End of section 26
