Download The maxillary bones support the teeth of the upper jaw and

The maxillary bones support the teeth of the upper jaw and contribute to much of the skeleton of the upper
face. Each bone consists of a body and four processes: the frontal, zygomatic, alveolar and palatine
processes. The body contains the maxillary air sinus (see below).
The frontal process of the maxilla projects postero-superiorly from the body of the maxilla and is situated
between the nasal bone in front and the lacrimal bone behind. The process articulates apically with the
frontal’s nasal part, the anterior border with the nasal bone and the posterior border with the lacrimal bone.
The frontal process’s lateral surface is divided into two areas by the vertically running anterior lacrimal crest.
Behind the crest, the bone is grooved for the nasolacrimal canal. The medial surface of the frontal process
shows an obliquely running ethmoidal crest. To this is attached the middle nasal concha. This surface
becomes part of the lateral wall of the nasal wall.
The zygomatic process of the maxilla projects laterally from the body. It is pyramidal in shape and has a
roughened supero-lateral surface for articulation with the zygomatic bone. Its posterior surface is smooth and
concave and forms part of the anterior boundary of the infratemporal fossa (see below).
The alveolar process of the maxilla extends inferiorly from the body of the maxilla and supports the teeth
within bony sockets. Each maxilla can contain a full quadrant of eight permanent teeth or five deciduous
teeth. The form of the alveolus is related to the functional demands put upon the teeth. For example, when
the teeth are extracted, the alveolus resorbs.
The processes consists of two parallel plates of cortical bone, the buccal and palatal alveolar plates, between
which lie the sockets of individual teeth. The sockets are separated by inter-alveolar or interdental septa. The
floor of the socket has been termed the ‘fundus’, and the rim is called the’ alveolar crest’. The form and depth
of each socket is defined by the form and length of the root it supports. The sockets thus show considerable
variation. In multi-rooted teeth, the sockets are divided by interradicular septa. The apical regions of the
sockets of anterior teeth are closely related to the nasal fossae, whereas those of posterior teeth are related
to the maxillary sinus. In the midline, the alveolar processes of the maxillary bones meet at the intermaxillary
suture.
The palatine process of the maxilla extends horizontally from the medial surface of the maxilla where the
body meets the alveolar process. Posteriorly, the boundary between the palatine and alveolar processes is
sharp. Anteriorly, the boundary is less well defined. The medial edge of the palatine process is for articulation
with the opposite palatine process at the median palatine suture. Behind the central incisors, the medial edge
shows evidence of the incisive fossa. Through this pass the nasopalatine nerves and branches of the greater
palatine vessels. An incisive canal runs through the palatine process in the region of the incisive fossa. The
medial edge is thickened on its nasal surface to contribute to the nasal crest, a structure that articulates with
the inferior border of the vomer. Both the nasal and oral surfaces of the palatine process are concave. Unlike
the nasal surface, the oral surface of the palatine process is rough and irregular, forming palatine grooves
and spines. The posterior edge of the palatine process articulates with the horizontal plate of a palatine bone
at the transverse palatine suture.
The maxillary bones show many articulations. On the face, the maxillary bones articulate with each other, the
nasal bones, the nasal cartilages and the frontal bone. Laterally, they articulate with the zygomatic bones.
Each maxillary bone also joins with the vomer, the septal cartilage, the lacrimal bone, the ethmoid bone and
the inferior nasal concha to contribute to the skeleton of the nasal fossa and the orbit.
Maxillary Sinuses
These are the largest of the paranasal sinuses. They are situated in the bodies of the maxillary bones.
The maxillary sinus is pyramidal in shape. The base or medial wall forms part of the lateral wall of the nose
and the apex extends into the zygomatic process of the maxilla. The roof of the sinus is part of the floor of the
orbit, while the alveolar process and part of the palatine process of the maxilla form the floor of the sinus. The
anterior wall of the maxillary sinus is the facial surface of the maxilla and the posterior wall is the
infratemporal surface of the maxilla. The sinus may be partially divided by incomplete bony septa.
The medial wall of the maxillary sinus has the opening (ostium) of the sinus and the roof contains the
infra-orbital canal, which transmits the infra-orbital nerve and vessels. The floor of the sinus lies below the
level of the floor of the nose and is related to the roots of the cheek teeth. As the size of the sinus varies
considerably, this relationship will also vary. Usually, at least the second premolar and first molar are related
to the floor of the sinus. However, the sinus may extend anteriorly to the first premolar, and sometimes even
to the canine, and posteriorly to the third molar tooth. The anterior wall of the maxillary sinus contains a fine
canal (canal sinuosus), which transmits the anterior superior alveolar nerve and vessels. The nerve arises
from the infra-orbital nerve near the midpoint of the infra-orbital canal; it passes downwards and is distributed
to the anterior teeth. The posterior superior alveolar nerve and vessels pass through canals in the posterior
surface of the sinus.
In an isolated maxillary bone, the ostium of the maxillary sinus is large. However, the ostium in an intact
specimen is considerably reduced by portions of the perpendicular plate of the palatine bone, the uncinate
process of the ethmoid bone, the inferior nasal concha, the lacrimal bone and by the overlying nasal mucosa
(see below). The ostium lies high up at the back of the medial wall of the maxillary sinus, being unfavorably
situated for drainage. It opens into the posterior part of the ethmoidal infundibulum, and hence into the hiatus
semilunaris of the middle meatus of the lateral wall of the nose. An accessory ostium is sometimes present
behind the major ostium.
The innervation of the maxillary sinus is derived from the maxillary nerve via its infra-orbital and posterior,
middle and anterior superior alveolar branches. The arterial supply to the sinus is derived chiefly from the
maxillary artery via its posterior superior alveolar, anterior superior alveolar, infra-orbital and greater palatine
branches. The veins draining the sinus correspond to the arteries and pass into the facial vein or the
pterygoid venous plexus. The lymphatics pass to the submandibular nodes.
Infratemporal Fossae
The infratemporal fossa is the space located deep to the ramus of the mandible.
The fossa is bounded anteriorly by the posterior surface of the maxilla and posteriorly by the styloid
apparatus, carotid sheath and deep part of the parotid gland. Medially, the lateral pterygoid plate and the
superior constrictor muscle of the pharynx can be found. Laterally lies the ramus of the mandible. The roof is
formed by the infratemporal surface of the greater wing of the sphenoid. The infratemporal fossa has no
anatomical floor; it is continuous with tissue spaces in the neck.
The infratemporal fossa communicates with the temporal fossa, deep to the zygomatic arch, and
communicates with the pterygopalatine fossa through the pterygomaxillary fissure. At the base of the
cranium, the foramen ovale and foramen spinosum enter the fossa through the sphenoid bone. The foramen
lacerum and the petrotympanic, squamotympanic and petrosquamous fissures are also found close to the
infratemporal fossa. On the medial surface of the ramus of the mandible is the mandibular foramen.
The Contents of the Infratemporal Fossa
i) The major structures which occupy the infratemporal fossa are:
ii) The lateral and medial pterygoid muscles
iii) The mandibular division of the trigeminal nerve
iv) The chorda tympani branch of the facial nerve
v) The otic parasympathetic ganglion
vi) The maxillary artery and branches
The pterygoid venous plexus
The key to understanding the relationships of structures within the infratemporal fossa is the lateral pterygoid
muscle. This lies in the roof of the fossa, running antero-posteriorly in a horizontal plane from the region of
the pterygoid plates to the mandibular condyle. It consists of two heads, an upper head and a lower head.
Deep to the muscle arise the branches of the mandibular nerve and the main origin of the medial pterygoid
muscle. Superficially lies the maxillary artery. The buccal branch of the mandibular nerve passes between the
two heads of the lateral pterygoid muscle. The medial pterygoid muscle and the lingual and inferior alveolar
nerves emerge below the inferior border of the lateral pterygoid muscle. The deep temporal nerves emerge
from the superior border of the lateral pterygoid muscle. At the upper border emerge the deep temporal
nerves and vessels. Concentrated around and within the lateral pterygoid muscle lies a venous network, the
pterygoid venous plexus.
Nasal Mucosa
Above the superior concha, the mucosa is termed olfactory mucosa because it contains the olfactory cells. In
vivo, this mucosa has a distinct yellowish color. In contrast, the remaining nasal mucosa is of the respiratory
type, also termed the ‘ciliated columna’, and appears pink. This is particularly thick and well vascularized at
the free margins of the nasal conchae.
Nerve Supply
Special sensation related to olfaction is associated with the olfactory nerves, the first cranial nerves. General
sensation to the nasal mucosa is related to branches from the ophthalmic and maxillary divisions of the
trigeminal nerves, the fifth cranial nerves.
The olfactory epithelium is located in the roof of the nasal cavity, extending onto the lateral walls of the nasal
fossae, above the superior nasal conchae and the uppermost part of the nasal septum. Filaments of the
olfactory nerves, about 20 on each side, pass upwards through the cribriform plate of the ethmoid bone into
the cranial cavity to synapse in the olfactory bulbs. Each filament is ensheathed by the meninges. Thus, a
potential pathway exists for the spread of infection from the nose to the cranial cavity.
The anterior ethmoidal nerve is the only branch of the ophthalmic nerve, which supplies the nasal mucosa. It
arises from the nasociliary nerve and mainly supplies an area in front of the nasal conchae. It also innervates
the anterior extremities of the middle and inferior conchae. After leaving the orbit through the anterior
ethmoidal foramen, the anterior ethmoidal nerve enters the cranial cavity onto the cribriform plate of the
ethmoid. It leaves the cranial cavity through a small slit near the crista galli and enters the roof of the nasal
cavity. Here, the nerve runs in a groove on the inner surface of the nasal bone. The anterior ethmoidal nerve
passes downwards and forwards and gives rise to lateral and medial internal nasal branches. The lateral
internal nasal branches pass to the lateral wall of the nose whereas the medial internal nasal branches run to
the nasal septum. When the anterior ethmoidal nerve emerges at the inferior margin of the nasal bone it
becomes the external nasal nerve.
The maxillary nerve contributes many branches, which supply the nasal mucosa. The infra-orbital and the
posterior superior alveolar nerves arise directly from the maxillary nerve. The posterior superior nasal, greater
palatine and nasopalatine nerves arise indirectly by way of the pterygopalatine ganglion.
The infra-orbital nerve is the terminal branch of the maxillary nerve. After passing onto the face at the
infra-orbital foramen, it provides a nasal branch, which supplies the skin of the vestibule and the mobile part
of the nasal septum. The anterior superior alveolar branch of the infra-orbital nerve also supplies nasal
mucosa. Its nasal branch passes through a small canal in the lateral wall of the nose, below the level of the
inferior concha, to innervate the anterior part of the inferior meatus and the adjacent part of the floor of the
nose and adjoining nasal septum.
The posterior superior nasal nerve originates at the pterygopalatine ganglion. It enters the back of the nasal
cavity through the sphenopalatine foramen and gives off lateral and medial branches. The lateral branches
supply the postero-superior part of the lateral wall of the nose around the superior and middle nasal conchae.
The medial branches cross the roof of the nasal cavity to supply the septum overlying the posterior part of the
perpendicular plate of the ethmoid.
The greater (anterior) palatine nerve also arises from the pterygopalatine ganglion. It descends in the greater
palatine canal where it gives off posterior inferior nasal branches. These branches pass through small
openings in the perpendicular plate of the palatine bone to supply the postero-inferior portion of the lateral
wall of the nose, below and including the middle meatus.
The nasopalatine nerve passes from the pterygopalatine ganglion into the nasal cavity through the
sphenopalatine foramen. It runs across the roof of the nasal cavity to reach the back of the nasal septum. It
then passes downwards and forwards, lying in a groove on the vomer, to supply the postero-inferior part of
the septum. The floor of the nose is supplied anteriorly by the nasal branch of the anterior superior alveolar
nerve and posteriorly by the nasal branches of the greater (anterior) palatine and by the nasopalatine nerves.
Autonomic fibers to glands and vessels in the nose are distributed with the above-mentioned branches of the
maxillary nerve via the pterygopalatine ganglion. In addition, it is presumed that the autonomic fibers are
distributed with the anterior ethmoidal nerve via the ciliary ganglion.
Arterial Supply
The general distribution of the arteries is similar to that of the nerves. The main vessels arise from the
ophthalmic and maxillary arteries, with small contributions from the facial artery.
The ophthalmic artery provides anterior and posterior ethmoidal branches to the nasal cavity. The anterior
ethmoidal artery accompanies the anterior ethmoidal nerve and supplies the anterior parts of the lateral wall
and the nasal septum. Its terminal branch is the external nasal artery. The posterior ethmoidal artery supplies
a small part of lateral wall of the nose around the superior nasal concha and the postero-superior region of
the nasal septum.
The sphenopalatine artery is the terminal branch of the maxillary artery in the pterygopalatine fossa. It enters
the lateral wall of the nose through the sphenopalatine foramen. The artery accompanies the posterior
superior nasal nerve and gives off branches to supply much of the posterior part of the lateral wall of the
nose. These branches for part of their course lie within the middle and inferior nasal conchae. The
sphenopalatine artery crosses the roof of the nasal cavity to supply the postero-inferior part of the nasal
septum.
The greater palatine artery is also a branch of the maxillary artery in the pterygopalatine fossa. It
accompanies the greater palatine nerve in the greater palatine canal and gives branches supplying the
inferior meatus. After passing onto the hard palate through the greater palatine foramen, the greater palatine
artery gives a branch that passes up through the incisive canal to supply the anterior part of the nasal
septum.
The superior labial branch of the facial artery is the main source of supply of the anterior part of the nasal
septum.
Venous and lymphatic supply
There are conspicuous venous plexuses in the lateral walls of the nasal fossae and in the nasal septum,
particularly inferiorly. Indeed, the plexuses are said to resemble plexuses in erectile tissue. Consequently, the
nasal cavity is susceptible to blockage should the plexuses become engorged.
The veins draining the nose essentially correspond to the arteries. Veins from the posterior part of the nose
generally pass to the sphenopalatine vein, which runs back through the sphenopalatine foramen to drain into
the pterygoid venous plexus. Mainly veins accompanying the anterior ethmoidal arteries, veins passing to the
ophthalmic or the facial veins, drain the anterior part of the nose.
Lymphatics in the anterior part of the nose drain into the submandibular lymph nodes. The lymphatics
posteriorly drain into the upper deep cervical nodes.