The pyramid-shaped maxillary sinus (or antrum of Highmore) is the largest of the

paranasal sinus Paranasal sinuses are a group of four paired skeletal pneumaticity, air-filled spaces that surround the nasal cavity. The maxillary sinuses are located under the eyes; the frontal sinuses are above the eyes; the Ethmoid sinus, ethmoidal sinuses a ...

es, located in the

maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...

. It drains into the middle meatus of the noseHuman Anatomy, Jacobs, Elsevier, 2008, page 209-210 through the semilunar hiatus. It is located to the side of the

nasal cavity The nasal cavity is a large, air-filled space above and behind the nose in the middle of the face. The nasal septum divides the cavity into two cavities, also known as fossae. Each cavity is the continuation of one of the two nostrils. The nas ...

, and below the orbit.

Structure

It is the largest air sinus in the body. It has a mean volume of about 10 ml. It is situated within the body of the maxilla, but may extend into its zygomatic and

alveolar processes The alveolar process () is the portion of bone containing the tooth sockets on the jaw bones (in humans, the maxilla and the mandible). The alveolar process is covered by gums within the mouth, terminating roughly along the line of the mandibular ...

when large. It is pyramid-shaped, with the apex at the maxillary

zygomatic process The zygomatic processes (aka. malar) are three processes (protrusions) from other bones of the skull which each articulate with the zygomatic bone. The three processes are: * Zygomatic process of frontal bone from the frontal bone * Zygomatic ...

, and the base represented by the lateral nasal wall. It 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 In the human skull, the zygomatic bone (from ), also called cheekbone or malar bone, is a paired irregular bone, situated at the upper and lateral part of the face and forming part of the lateral wall and floor of the orbit, of the temporal fos ...

; and an infraorbital recess pointed superiorly, bounded by the inferior orbital surface of the maxilla. The medial wall is composed primarily of

cartilage Cartilage is a resilient and smooth type of connective tissue. Semi-transparent and non-porous, it is usually covered by a tough and fibrous membrane called perichondrium. In tetrapods, it covers and protects the ends of long bones at the joints ...

Walls

The nasal wall of the maxillary sinus, or base, presents, in the disarticulated bone, a large, irregular aperture that communicates with the

. In the articulated skull this aperture is much reduced in size by the following bones: * the uncinate process of the ethmoid above, * the ethmoidal process of the

inferior nasal concha The inferior nasal concha (inferior turbinated bone or inferior turbinal/turbinate) is one of the three paired nasal conchae in the human nose, nose. It extends horizontally along the lateral wall of the nasal cavity and consists of a wikt:lam ...

below, * the vertical part of the

palatine A palatine or palatinus (Latin; : ''palatini''; cf. derivative spellings below) is a high-level official attached to imperial or royal courts in Europe since Roman Empire, Roman times.

behind, * and a small part of the lacrimal above and in front. The sinus communicates through an opening into the semilunar hiatus on the lateral nasal wall. The medial wall is composed primarily of

. 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, 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 maxillary

molar teeth The molars or molar teeth are large, flat teeth at the back of the mouth. They are more developed in mammals. They are used primarily to grind food during chewing. The name ''molar'' derives from Latin, ''molaris dens'', meaning "millstone toot ...

; in some cases the floor can be perforated by the apices of the teeth. The roof is formed by the floor of the orbit. It is traversed by infraorbital nerves and vessels.

Features

The infraorbital canal forms a ridge at the junction of the roof and anterior wall of the sinus; additional ridges are sometimes seen in the posterior wall of the cavity and are caused by the alveolar canals.

Innervation

The mucous membranes receive their mucomotor

postganglionic In the autonomic nervous system, nerve fibers from the ganglion to the wikt:effector, effector organ are called postganglionic nerve fibers. Neurotransmitters The neurotransmitters of postganglionic fibers differ: * In the parasympathetic div ...

parasympathetic The parasympathetic nervous system (PSNS) is one of the three divisions of the autonomic nervous system, the others being the sympathetic nervous system and the enteric nervous system. The autonomic nervous system is responsible for regulat ...

nerve fibres from the pterygopalatine ganglion. The superior alveolar (anterior, middle, and posterior) nerves, branches of the

maxillary nerve In neuroanatomy, the maxillary nerve (V) is one of the three branches or divisions of the trigeminal nerve, the fifth (CN V) cranial nerve. It comprises the principal functions of Sense, sensation from the maxilla, nasal cavity, Sinus (anatomy ...

provide sensory innervation.

Microanatomy

The sinus is lined with mucoperiosteum, with cilia that beat toward the ostia. This membranous lining is also referred to as the Schneiderian membrane, which is

histologically Histology, also known as microscopic anatomy or microanatomy, is the branch of biology that studies the microscopic anatomy of biological tissue (biology), tissues. Histology is the microscopic counterpart to gross anatomy, which looks at large ...

a bilaminar membrane with pseudostratified ciliated columnar epithelial cells on the internal (or cavernous) side and

periosteum The periosteum is a membrane that covers the outer surface of all bones, except at the articular surfaces (i.e. the parts within a joint space) of long bones. (At the joints of long bones the bone's outer surface is lined with "articular cartila ...

on the osseous side. The size of the sinuses varies in different

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

s, and even on the two sides of the same skull.Bell, G.W., et al. Maxillary sinus disease: diagnosis and treatment, ''British Dental Journal'' 210, 113 - 118 (2011) at http://www.nature.com/bdj/journal/v210/n3/full/sj.bdj.2011.47.html

Relations

The roof of the sinus is also the floor of the

orbit In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an ...

. Posterior to the sinus and its wall are the pterygopalatine fossa and the infratemporal fossa.

Variation

After puberty, the maxillary sinus rapidly increases in size. Its size is variable in the adult; if large, it may extend into the

and alveolar process of the maxilla. Extension into the maxillary alveolar process may cause the roots of the molars and even premolars to lie just beneath the floor of the sinus or even project through the floor and into the sinus; in such cases, the roots of the teeth are typically surrounded by a thin layer of bone, but may sometimes lie directly underneath the mucous membrane of the sinus. Projection of the roots into the maxillary sinus is more common in advanced age due to

bone resorption Bone resorption is resorption of bone tissue, that is, the process by which osteoclasts break down the tissue in bones and release the minerals, resulting in a transfer of calcium from bone tissue to the blood. The osteoclasts are multi-nuclea ...

. In such cases, tooth extraction can create a

fistula In anatomy, a fistula (: fistulas or fistulae ; from Latin ''fistula'', "tube, pipe") is an abnormal connection (i.e. tube) joining two hollow spaces (technically, two epithelialized surfaces), such as blood vessels, intestines, or other h ...

between the

oral cavity A mouth also referred to as the oral is the body orifice through which many animals ingest food and vocalize. The body cavity immediately behind the mouth opening, known as the oral cavity (or in Latin), is also the first part of the alime ...

and the sinus that nevertheless usually resolves spontaneously. An accessory maxillary ostium (found in 0% to 42% of the population) is an additional natural opening in the lateral nasal wall that provides communication between the maxillary sinus and the nasal cavity, apart from the primary or natural maxillary ostium. It is usually located in the posterior fontanelle of the lateral nasal wall, part of the middle meatus. While this ostium is listed as an anatomical variation, it has a role in the development of maxillary

sinusitis Sinusitis, also known as rhinosinusitis, is an inflammation of the mucous membranes that line the sinuses resulting in symptoms that may include production of thick nasal mucus, nasal congestion, facial congestion, facial pain, facial pressure ...

Development

Maxillary sinus is the first

es to form. At birth, it is about 6 to 8 cm³ in volume, elongated, as is orientated in antero-posterior direction, located at the next to the medial orbital wall of the eye. The lateral wall of the maxillary sinus goes beneath the medial orbital wall during the first year of life, extends laterally pass the

infraorbital groove The infraorbital groove (or sulcus) is located in the middle of the posterior part of the orbital surface of the maxilla. Its function is to act as the passage of the infraorbital artery, the infraorbital vein, and the infraorbital nerve. Struc ...

by the age of four years, and reach the

by the age of nine years. After the first permanent tooth erupted at the age of six to seven, aeration of maxillary sinus is the main growth feature. At the final phase of aeration, the floor of maxillary sinus is four to five millimetres below the floor of

. However, timing of maxillary sinus growth is variable in different people.

Clinical significance

Maxillary sinusitis

Maxillary

inflammation Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', '' ...

of the maxillary sinuses. The

symptom Signs and symptoms are diagnostic indications of an illness, injury, or condition. Signs are objective and externally observable; symptoms are a person's reported subjective experiences. A sign for example may be a higher or lower temperature ...

s of sinusitis are headache, usually near the involved sinus, and foul-smelling nasal or pharyngeal discharge, possibly with some systemic signs of infection such as fever and weakness. The skin over the involved sinus can be tender, hot, and even reddened due to the inflammatory process in the area. On radiographs, there is opacification (or cloudiness) of the usually translucent sinus due to retained mucus.Illustrated Anatomy of the Head and Neck, Fehrenbach and Herring, Elsevier, 2012, page 67 Maxillary sinusitis is common due to the close anatomic relation of the frontal sinus, anterior

ethmoidal sinus The ethmoid sinuses or ethmoid air cells of the ethmoid bone are one of the four paired paranasal sinuses. Unlike the other three pairs of paranasal sinuses which consist of one or two large cavities, the ethmoidal sinuses entail a number of small ...

and the maxillary teeth, allowing for easy spread of infection. Differential diagnosis of dental problems needs to be done due to the close proximity to the teeth since the pain from sinusitis can seem to be dentally related. 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. The maxillary sinus may drain into the

mouth A mouth also referred to as the oral is the body orifice through which many animals ingest food and animal communication#Auditory, vocalize. The body cavity immediately behind the mouth opening, known as the oral cavity (or in Latin), is also t ...

via an abnormal opening, an oroantral fistula, a particular risk after tooth extraction.

Oro-antral communication (OAC)

An OAC is an abnormal physical communication between the maxillary sinus and the mouth. This opening is only present when the structures that normally separates the mouth and sinus into 2 separate compartments are lost. There are many causes of an OAC. The most common reason is following extraction of a posterior maxillary (upper)

premolar The premolars, also called premolar Tooth (human), teeth, or bicuspids, are transitional teeth located between the Canine tooth, canine and Molar (tooth), molar teeth. In humans, there are two premolars per dental terminology#Quadrant, quadrant in ...

or molar tooth. Other causes include trauma, pathology (e.g. tumours or cysts), infection or iatrogenic damage during surgery. Iatrogenic damage during dental treatment accounts for nearly half of the incidence of dental-related maxillary sinusitis. There is always a thin layer of mucous membrane (''Schneiderian membrane'') and usually bone between the roots of the upper back teeth and the floor of the maxillary sinus. However, the bone can vary in thickness in different individuals, ranging from complete absence to 12mm thick. Therefore, in certain individuals the membrane +/- the bony floor of the sinus can be perforated easily, creating an opening into the mouth when a tooth is extracted. An OAC that is smaller than 2mm can heal spontaneously i.e. closure of the opening. Those that are larger than 2mm have a higher chance of developing into oro-antral fistula (OAF). The passage is only defined as an OAF if it is persistent and lined by

epithelium Epithelium or epithelial tissue is a thin, continuous, protective layer of cells with little extracellular matrix. An example is the epidermis, the outermost layer of the skin. Epithelial ( mesothelial) tissues line the outer surfaces of man ...

. Epithelialisation happens when an OAC persist for at least 2–3 days and oral epithelial cells proliferate to line the defect. Large defects (more than 2mm) should be surgically closed as soon as possible to avoid accumulation of food and saliva which could contaminate the maxillary sinus, leading to infection (sinusitis). Various surgical techniques can be employed to manage an OAF but the most common involves pulling and stitching some soft tissue from the gum to cover the opening (i.e. soft tissue flap).

Sinusitis treatment

Traditionally the treatment of acute maxillary sinusitis is usually prescription of a broad-spectrum

cephalosporin The cephalosporins (sg. ) are a class of β-lactam antibiotics originally derived from the fungus '' Acremonium'', which was previously known as ''Cephalosporium''. Together with cephamycins, they constitute a subgroup of β-lactam antibio ...

antibiotic resistant to beta-lactamase, administered for 10 days. Recent studies have found that the cause of chronic sinus infections lies in the nasal mucus, not in the nasal and sinus tissue targeted by standard treatment. This suggests a beneficial effect in treatments that target primarily the underlying and presumably damage-inflicting nasal and sinus membrane inflammation, instead of the secondary bacterial infection that has been the primary target of past treatments for the disease. Also, surgical procedures with chronic sinus infections are now changing with the direct removal of the mucus, which is loaded with toxins from the inflammatory cells, rather than the inflamed tissue during surgery. Leaving the mucus behind might predispose early recurrence of the chronic sinus infection. If any surgery is performed, it is to enlarge the ostia in the lateral walls of the nasal cavity, creating adequate drainage.

Cancer

Carcinoma Carcinoma is a malignancy that develops from epithelial cells. Specifically, a carcinoma is a cancer that begins in a tissue that lines the inner or outer surfaces of the body, and that arises from cells originating in the endodermal, mesoder ...

of the maxillary sinus may invade the palate and cause dental pain. It may also block the nasolacrimal duct. Spread of the tumor into the orbit causes proptosis. File:Diagram showing maxillary sinus cancer that has spread to the brain CRUK 167.svg, Maxillary sinus cancer that has spread to the brain File:Diagram showing maxillary sinus cancer that has spread to the lymph nodes CRUK 168.svg, Maxillary sinus cancer that has spread to the lymph nodes

Age

With age, the enlarging maxillary sinus may even begin to surround the roots of the maxillary posterior teeth and extend its margins into the body of the zygomatic bone. If the maxillary posterior teeth are lost, the maxillary sinus may expand even more, thinning the bony floor of the alveolar process so that only a thin shell of bone is present.

History

The maxillary sinus was first discovered and illustrated by

Leonardo da Vinci Leonardo di ser Piero da Vinci (15 April 1452 - 2 May 1519) was an Italian polymath of the High Renaissance who was active as a painter, draughtsman, engineer, scientist, theorist, sculptor, and architect. While his fame initially rested o ...

, but the earliest attribution of significance was given to Nathaniel Highmore, the British surgeon and anatomist who described it in detail in his 1651 treatise.Merriam-Webster's Medical Desk Dictionary Revised Ed. 2002, pg 49.

References

External links

* * * (, ) * Maxillary Sinus: Normal Anatomy & Variants at http://uwmsk.org/sinusanatomy2/Maxillary-Normal.html * Cancer in the maxillary sinus, Stanford University at http://cancer.stanford.edu/headneck/sinus/sinus_max.html {{Authority control Bones of the head and neck Otorhinolaryngology Rhinology Sinus surgery