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

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

es, and drains into the

middle meatus In anatomy, the term nasal meatus can refer to any of the three meatuses (passages) through the skulls nasal cavity: the superior meatus (''meatus nasi superior''), middle meatus (''meatus nasi medius''), and inferior meatus (''meatus nasi inferi ...

of the nose through the osteomeatal complex.Human Anatomy, Jacobs, Elsevier, 2008, page 209-210

Structure

It is the largest air sinus in the body. Found in the body of the maxilla, this sinus has three recesses: an alveolar recess pointed inferiorly, bounded by the

alveolar process The alveolar process () or alveolar bone is the thickened ridge of bone that contains the tooth sockets on the jaw bones (in humans, the maxilla and the mandible). The structures are covered by gums as part of the oral cavity. The synonymous ...

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 Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck ...

. The ostia for drainage are located high on the medial wall and open into the semilunar hiatus of the lateral

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 nasal ...

; because of the position of the ostia, gravity cannot drain the maxillary sinus contents when the head is erect (see pathology). The ostium of the maxillary sinus is high up on the medial wall and on average is 2.4 mm in diameter; with a mean volume of about 10 ml. The sinus is lined with

mucoperiosteum Mucoperiosteum is a compound structure consisting of mucous membrane and underlying periosteum. It includes epithelium and lamina propria, but attaches directly to the periosteum of underlying bone without the usual submucosa. It consists of loos ...

, with cilia that beat toward the ostia. This membranous lining is also referred to as the Schneiderian membrane, which is histologically a bilaminar membrane with pseudostratified ciliated columnar epithelial cells on the internal (or cavernous) side and periosteum on the

osseous A bone is a rigid organ that constitutes part of the skeleton in most vertebrate animals. Bones protect the various other organs of the body, produce red and white blood cells, store minerals, provide structure and support for the body, a ...

side. The size of the sinuses varies in different

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

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 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 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 enteric nervous system is sometimes considered part of ...

nerve fibres for mucous

secretion 440px Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classic ...

from the pterygopalatine ganglion. The preganglionic parasympathetic fibres are coming to this ganglion through the greater petrosal nerve (a branch of the

facial nerve The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste ...

) and the nerve of the pterygoid canal. 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 sensation from the maxilla, nasal cavity, sinuses, the pala ...

provide

sensory innervation Cutaneous innervation refers to the area of the skin which is supplied by a specific cutaneous nerve. Dermatomes are similar; however, a dermatome only specifies the area served by a spinal nerve. In some cases, the dermatome is less specific (whe ...

Walls

The nasal wall of the maxillary sinus, or base, presents, in the disarticulated bone, a large, irregular aperture, communicating 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 below, * the vertical part of the palatine 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. 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

, 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 ...

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

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 by the age of four years, and reach the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates 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. T ...

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 milimetres below the floor of

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

Clinical significance

Maxillary sinusitis

CT Brain showing air-fluid levels of bilateral maxillary air sinuses post brain trauma

Maxillary sinusitis is

inflammation Inflammation (from la, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants, and is a protective response involving immune cells, blood vessels, and molec ...

of the maxillary sinuses. The

symptom Signs and symptoms are the observed or detectable signs, and experienced symptoms of an illness, injury, or condition. A sign for example may be a higher or lower temperature than normal, raised or lowered blood pressure or an abnormality showi ...

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 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 In animal anatomy, the mouth, also known as the oral cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is also the cavity lying at the upper end of the alimentary canal, bounded on ...

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 teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth ...

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 one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellul ...

. 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 antibiotics ...

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, mesoderm ...

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 Exophthalmos (also called exophthalmus, exophthalmia, proptosis, or exorbitism) is a bulging of the eye anteriorly out of the orbit. Exophthalmos can be either bilateral (as is often seen in Graves' disease) or unilateral (as is often seen i ...

. 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 14522 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 on ...

, 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