Paranasal sinus
Encyclopedia
Paranasal sinuses are a group of four paired air-filled spaces
that surround the nasal cavity (maxillary sinuses), above and between the eyes (ethmoid sinuses
and frontal sinuses), and behind the ethmoids (sphenoid sinuses). The sinuses are named for the facial bones
behind which they are located.
s within which the sinuses lie:
The paranasal air sinuses are lined with respiratory epithelium
(ciliated pseudostratified columnar epithelium).
. This process begins prenatally, and it continues through the course of an organism's lifetime.
s, and crocodilians). In non-humans, the bones occupied by sinuses are quite variable.
via small orifices called ostia
. These become blocked easily by allergic inflammation, or by swelling in the nasal lining which occurs with a cold
. If this happens, normal drainage of mucus
within the sinuses is disrupted, and sinusitis
may occur.
These conditions may be treated with drugs such as pseudoephedrine
, which causes vasoconstriction in the sinuses, reducing inflammation, by traditional techniques of nasal irrigation
, or by corticosteroid
.
Malignancies of the paranasal sinuses comprise approximately 0.2% of all malignancies. About 80% of these malignancies arise in the maxillary sinus. Men are much more often affected than women. They most often occur in the age group between 40 and 70 years. Carcinoma
s are more frequent than sarcoma
s. Metastases are rare. Tumours of the sphenoid and frontal sinuses are extremely rare.
word meaning a fold or pocket
; in particular the front pocket in a toga
.
Skeletal pneumaticity
Skeletal pneumaticity is the presence of air spaces within bones. Skeletal pneumaticity exists only in synapsids and archosaurs. It is generally produced during development by excavation of bone by pneumatic diverticula from an air-filled space such as the lungs or nasal cavity...
that surround the nasal cavity (maxillary sinuses), above and between the eyes (ethmoid sinuses
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 frontal sinuses), and behind the ethmoids (sphenoid sinuses). The sinuses are named for the facial bones
Facial bones
The facial skeleton, splanchnocranium or viscerocranium consists of part of skull that is derived from branchial arches. The facial bones are the bones of the anterior and lower human skull.Most sources include:* Inferior nasal concha...
behind which they are located.
Types in humans
Humans possess a number of paranasal sinuses, divided into subgroups that are named according to the boneBone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...
s within which the sinuses lie:
- the maxillary sinusMaxillary sinusThe pyramid shaped maxillary sinus is the largest of the paranasal sinuses, and drains into the nose. It is present at birth as rudimentary air cells, and develops throughout childhood.-General characteristics:...
es, also called the maxillary antrechea and the largest of the paranasal sinuses, are under the eyeHuman eyeThe human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...
s, in the maxillary bones. - the frontal sinusFrontal sinusSinuses are mucosa-lined airspaces within the bones of the face and skull. The frontal sinuses, situated behind the superciliary arches, are absent at birth, but are generally fairly well developed between the seventh and eighth years, only reaching their full size after puberty...
es, superior to the eyes, in the frontal boneFrontal boneThe frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
, which forms the hard part of the foreheadForeheadFor the Arsenal striker see GervinhoIn human anatomy, the forehead is the fore part of the head. It is, formally, an area of the head bounded by three features, two of the skull and one of the scalp. The top of the forehead is marked by the hairline, the edge of the area where hair on the scalp...
. - the ethmoid sinusEthmoid sinusThe 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...
es, which are formed from several discrete air cells within the ethmoid boneEthmoid boneThe ethmoid bone is a bone in the skull that separates the nasal cavity from the brain. As such, it is located at the roof of the nose, between the two orbits. The cubical bone is lightweight due to a spongy construction. The ethmoid bone is one of the bones that makes up the orbit of the eye...
between the noseHuman noseThe visible part of the human nose is the protruding part of the face that bears the nostrils. The shape of the nose is determined by the ethmoid bone and the nasal septum, which consists mostly of cartilage and which separates the nostrils...
and the eyes. - the sphenoid sinuses, in the sphenoid boneSphenoid boneThe sphenoid bone is an unpaired bone situated at the base of the skull in front of the temporal bone and basilar part of the occipital bone.The sphenoid bone is one of the seven bones that articulate to form the orbit...
at the center of the skull base under the pituitary glandPituitary glandIn vertebrate anatomy the pituitary gland, or hypophysis, is an endocrine gland about the size of a pea and weighing 0.5 g , in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity covered by a dural fold...
.
The paranasal air sinuses are lined with respiratory epithelium
Respiratory epithelium
Respiratory epithelium is a type of epithelium found lining the respiratory tract, where it serves to moisten and protect the airways. It also functions as a barrier to potential pathogens and foreign particles, preventing infection and tissue injury by action of the mucociliary escalator.-...
(ciliated pseudostratified columnar epithelium).
Development
Paranasal sinuses form developmentally through excavation of bone by air-filled sacs (pneumatic diverticula) from 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...
. This process begins prenatally, and it continues through the course of an organism's lifetime.
Sinuses in animals
Paranasal sinuses occur in a variety of animals (including most mammals, birds, non-avian dinosaurDinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s, and crocodilians). In non-humans, the bones occupied by sinuses are quite variable.
Biological function
The biological role of the sinuses is debated, but a number of possible functions have been proposed:- Decreasing the relative weight of the front of the skull, and especially the bones of the face.
- Increasing resonance of the voiceHuman voiceThe human voice consists of sound made by a human being using the vocal folds for talking, singing, laughing, crying, screaming, etc. Its frequency ranges from about 60 to 7000 Hz. The human voice is specifically that part of human sound production in which the vocal folds are the primary...
. - Providing a buffer against blows to the face.
- Insulating sensitive structures like dental roots and eyes from rapid temperature fluctuations in the nasal cavity.
- Humidifying and heating of inhaled air because of slow air turnover in this region.
Ailments
The paranasal sinuses are joined to 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...
via small orifices called ostia
Sinus ostia
A sinus ostium is the opening that connects a sinus to the nasal cavity itself. It is a tight area that tends to have a higher percentage of cilia than the surrounding mucosa....
. These become blocked easily by allergic inflammation, or by swelling in the nasal lining which occurs with a cold
Common cold
The common cold is a viral infectious disease of the upper respiratory system, caused primarily by rhinoviruses and coronaviruses. Common symptoms include a cough, sore throat, runny nose, and fever...
. If this happens, normal drainage of mucus
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...
within the sinuses is disrupted, and sinusitis
Sinusitis
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...
may occur.
These conditions may be treated with drugs such as pseudoephedrine
Pseudoephedrine
Pseudoephedrine is a sympathomimetic drug of the phenethylamine and amphetamine chemical classes. It is used as a nasal/sinus decongestant and stimulant, or as a wakefulness-promoting agent....
, which causes vasoconstriction in the sinuses, reducing inflammation, by traditional techniques of nasal irrigation
Nasal irrigation
Nasal irrigation or nasal lavage or nose douche is the personal hygiene practice in which the nasal cavity is washed to flush out excess mucus and debris from the nose and sinuses. The practice is well-tolerated and beneficial with only minor side effects...
, or by corticosteroid
Corticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
.
Malignancies of the paranasal sinuses comprise approximately 0.2% of all malignancies. About 80% of these malignancies arise in the maxillary sinus. Men are much more often affected than women. They most often occur in the age group between 40 and 70 years. Carcinoma
Carcinoma
Carcinoma is the medical term for the most common type of cancer occurring in humans. Put simply, a carcinoma is a cancer that begins in a tissue that lines the inner or outer surfaces of the body, and that generally arises from cells originating in the endodermal or ectodermal germ layer during...
s are more frequent than sarcoma
Sarcoma
A sarcoma is a cancer that arises from transformed cells in one of a number of tissues that develop from embryonic mesoderm. Thus, sarcomas include tumors of bone, cartilage, fat, muscle, vascular, and hematopoietic tissues...
s. Metastases are rare. Tumours of the sphenoid and frontal sinuses are extremely rare.
Etymology
Sinus is a LatinLatin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
word meaning a fold or pocket
Pocket
A pocket is a bag- or envelope-like receptacle either fastened to or inserted in an article of clothing to hold small items. Pockets may also be attached to luggage, backpacks, and similar items...
; in particular the front pocket in a toga
Toga
The toga, a distinctive garment of Ancient Rome, was a cloth of perhaps 20 ft in length which was wrapped around the body and was generally worn over a tunic. The toga was made of wool, and the tunic under it often was made of linen. After the 2nd century BC, the toga was a garment worn...
.