Maxillary sinus
Encyclopedia
The pyramid shaped maxillary sinus (or antrum of Highmore) is the largest of the paranasal sinus
es, and drains into the nose. It is present at birth as rudimentary air cells, and develops throughout childhood.
, with cilia that beat toward the ostia. This membrane is also referred to as the "Schneiderian Membrane", which is histologically a bilaminar membrane with ciliated columnar epithelial cells on the internal (or cavernous) side and periosteum on the osseous side. The size of the sinuses varies in different skulls, and even on the two sides of the same skull.
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 mucous membranes receive their postganglionic parasympathetic nerve innervation for mucous
secretion
originating from the greater petrosal nerve (a branch of the facial nerve). The superior alveolar (anterior, middle, and posterior) nerves, branches of the maxillary nerve provide sensory innervation.
The maxillary sinus may drain into the mouth
via an abnormal opening, an oroantral fistula
, a particular risk after tooth extraction.
.
In the articulated skull this aperture is much reduced in size by the following bones:
The sinus communicates through an opening into the semilunar hiatus on the lateral nasal wall.
, transmitting the posterior superior alveolar vessels
and nerves
to the molar
teeth.
, and, if the sinus is of an average size, is on a level with the floor of the nose; if the sinus is 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 cases the floor is perforated by the apices of the teeth.
is inflammation
of the maxillary sinuses.
Maxillary sinusitis is common due to the close anatomical relation of the frontal sinus, anterior ethmoidal air sinus
and the maxillary teeth, allowing for easy spread of infection. Furthermore, the drainage orifice lies near the roof of the sinus, and so the maxillary sinus does not drain well, and infection develops more easily.
Paranasal sinus
Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity , above and between the eyes , and behind the ethmoids...
es, and drains into the nose. It is present at birth as rudimentary air cells, and develops throughout childhood.
General characteristics
Found in the body of the maxilla, this sinus has three recesses: an alveolar recess pointed inferiorly, bounded by the alveolar process of the maxilla; a zygomatic recess pointed laterally, bounded by the zygomatic bone; and an infraorbital recess pointed superiorly, bounded by the inferior orbital surface of the maxilla. The medial wall is composed primarily of cartilage. The ostia for drainage are located high on the medial wall and open into the semilunar hiatus of the lateral nasal cavity; because of the position of the ostia, gravity cannot drain the maxillary sinus contents when the head is erect. The sinus is lined with mucoperiosteumMucoperiosteum
Mucoperiosteum is a compound structure consisting of mucous membrane and of periosteum.It can be found in the palate....
, with cilia that beat toward the ostia. This membrane is also referred to as the "Schneiderian Membrane", which is histologically a bilaminar membrane with ciliated columnar epithelial cells on the internal (or cavernous) side and periosteum on the osseous side. The size of the sinuses varies in different skulls, and even on the two sides of the same skull.
The infraorbital canal
Infraorbital canal
Not to be confused with the infraorbital groove and infraorbital foramen, which are on opposite ends of the canal.One of the canals of the orbital surface of the maxilla, the infraorbital canal, opens just below the margin of the orbit...
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 mucous membranes receive their postganglionic parasympathetic nerve innervation for mucous
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
secretion
Secretion
Secretion is the process of elaborating, releasing, and oozing chemicals, or a secreted chemical substance from a cell or gland. In contrast to excretion, the substance may have a certain function, rather than being a waste product...
originating from the greater petrosal nerve (a branch of the facial nerve). The superior alveolar (anterior, middle, and posterior) nerves, branches of the maxillary nerve provide sensory innervation.
The maxillary sinus may drain into the mouth
Mouth
The mouth is the first portion of the alimentary canal that receives food andsaliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth....
via an abnormal opening, an oroantral fistula
Fistula
In medicine, a fistula is an abnormal connection or passageway between two epithelium-lined organs or vessels that normally do not connect. It is generally a disease condition, but a fistula may be surgically created for therapeutic reasons.-Locations:Fistulas can develop in various parts of the...
, a particular risk after tooth extraction.
Nasal wall/base
Its nasal wall, or base, presents, in the disarticulated bone, a large, irregular aperture, communicating with the nasal cavityNasal cavity
The nasal cavity is a large air filled space above and behind the nose in the middle of the face.- Function :The nasal cavity conditions the air to be received by the other areas of the respiratory tract...
.
In the articulated skull this aperture is much reduced in size by the following bones:
- the uncinate process of the ethmoidUncinate process of ethmoid boneIn the ethmoid bone, a curved lamina, the uncinate process, projects downward and backward from this part of the labyrinth; it forms a small part of the medial wall of the maxillary sinus, and articulates with the ethmoidal process of the inferior nasal concha....
above, - the ethmoidal process of the inferior nasal concha below,
- the vertical part of the palatinePalatine boneThe palatine bone is a bone in many species of the animal kingdom, commonly termed the palatum .-Human anatomy:...
behind, - and a small part of the lacrimalLacrimal boneThe lacrimal bone, the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders.-Lateral or orbital surface:...
above and in front.
The sinus communicates through an opening into the semilunar hiatus on the lateral nasal wall.
Posterior wall
On the posterior wall are the alveolar canalsAlveolar canals
The infratemporal surface of the maxilla is pierced about its center by the apertures of the alveolar canals, which transmit the posterior superior alveolar vessels and nerves....
, transmitting the posterior superior alveolar vessels
Posterior superior alveolar artery
The posterior superior alveolar artery is given off from the maxillary, frequently in conjunction with the infraorbital artery just as the trunk of the vessel is passing into the pterygopalatine fossa.-Branches:...
and nerves
Posterior superior alveolar nerve
The posterior superior alveolar branches arise from the trunk of the maxillary nerve just before it enters the infraorbital groove; they are generally two in number, but sometimes arise by a single trunk....
to the molar
Molar (tooth)
Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....
teeth.
Floor
The floor is formed by the alveolar process of the maxillaAlveolar process of maxilla
The alveolar process is the thickened ridge of bone that contains the tooth sockets on bones that bear teeth. It is also referred to as the alveolar bone. In humans, the tooth-bearing bones are the maxilla and the mandible...
, and, if the sinus is of an average size, is on a level with the floor of the nose; if the sinus is 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 cases the floor is perforated by the apices of the teeth.
Maxillary Sinusitis
Maxillary sinusitisSinusitis
Sinusitis is inflammation of the paranasal sinuses, which may be due to infection, allergy, or autoimmune issues. Most cases are due to a viral infection and resolve over the course of 10 days...
is inflammation
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
of the maxillary sinuses.
Maxillary sinusitis is common due to the close anatomical relation of the frontal sinus, anterior ethmoidal air sinus
Ethmoid sinus
The ethmoid sinus is each of the two paranasal sinuses within the ethmoid bone, comprising the ethmoidal air cells and filled with air. These are divided into anterior, middle and posterior group. The ethmoidal air cells consist of numerous thin-walled cavities situated in the ethmoidal labyrinth...
and the maxillary teeth, allowing for easy spread of infection. Furthermore, the drainage orifice lies near the roof of the sinus, and so the maxillary sinus does not drain well, and infection develops more easily.