Frontal sinus
Encyclopedia
Sinuses 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
. The frontal bone
is membranous at birth and there is rarely more than a recess until the bone tissue starts to ossify about age two. Consequently this structure does not show on radiographs before that time. Frontal sinuses are rarely symmetrical and the septum
between them frequently deviates to one or other side of the middle line. Sinus development begins in the womb, but only the maxillary
and ethmoid sinus
es are present at birth. Approximately 5% of people have absent frontal sinuses.
Their average measurements are as follows: height 28 mm, breadth 24 mm, depth 20 mm, creating a space of 6-7 ml.
Each opens into the anterior part of the corresponding middle meatus of the nose through the frontonasal duct
which traverses the anterior part of the labyrinth of the ethmoid. These structures then open into the hiatus semilunaris
in the middle meatus
.
The mucous membrane in this sinus is innervated by the supraorbital nerve
, which carries the postganglionic parasympathetic nerve fibers for mucous
secretion
from the ophthalmic nerve and supplied by the supraorbital artery and anterior ethmoidal artery
.
Through its copious mucus production, the sinus is an essential part of the immune defense/air filtration carried out by the nose. Nasal and sinal mucosae are ciliated and move mucus to the choanae and finally to the stomach. The thick upper layers of nasal mucus trap bacteria and small particles in tissue abundantly provided with immune cells, antibodies, and antibacterial proteins. The layers beneath are thinner and provide a substrate in which the cilia are able to beat and move the upper layer with its debris through the ostia
toward the choanae.
Inflammations of the frontal sinus can give rise to serious complications, as it is in close proximity to the orbit and cranial cavity (orbital cellulitis
, epidural and subdural abscess, meningitis
).
Superciliary arches
On the squama frontalis of the frontal bone of the skull, below the frontal eminences, and separated from them by a shallow groove, are two arched elevations, the superciliary arches; these are prominent medially, and are joined to one another by a smooth elevation named the glabella.Typically, the...
, are absent at birth, but are generally fairly well developed between the seventh and eighth years, only reaching their full size after puberty
Puberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...
. The frontal bone
Frontal bone
The 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....
is membranous at birth and there is rarely more than a recess until the bone tissue starts to ossify about age two. Consequently this structure does not show on radiographs before that time. Frontal sinuses are rarely symmetrical and the septum
Septum
In anatomy, a septum is a wall, dividing a cavity or structure into smaller ones.-In human anatomy:...
between them frequently deviates to one or other side of the middle line. Sinus development begins in the womb, but only the maxillary
Maxillary sinus
The 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:...
and ethmoid 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...
es are present at birth. Approximately 5% of people have absent frontal sinuses.
Their average measurements are as follows: height 28 mm, breadth 24 mm, depth 20 mm, creating a space of 6-7 ml.
Each opens into the anterior part of the corresponding middle meatus of the nose through the frontonasal duct
Frontonasal duct
The frontal air sinuses are lined by mucous membrane, and each communicates with the corresponding nasal cavity by means of a passage called the frontonasal duct....
which traverses the anterior part of the labyrinth of the ethmoid. These structures then open into the hiatus semilunaris
Hiatus semilunaris
The hiatus semilunaris is a crescent-shaped groove in the lateral wall of the nasal cavity just inferior to the ethmoidal bulla. It is the location of the openings for the frontal sinus, maxillary sinus, and anterior ethmoidal sinus...
in the middle meatus
Middle meatus
The middle meatus is a nasal opening or canal situated between the middle and inferior conchæ, and extends from the anterior to the posterior end of the latter....
.
The mucous membrane in this sinus is innervated by the supraorbital nerve
Supraorbital nerve
The supraorbital nerve is a terminal branch of the frontal nerve.It passes through the supraorbital foramen, and gives off, in this situation, palpebral filaments to the upper eyelid...
, which carries the postganglionic parasympathetic nerve fibers 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...
from the ophthalmic nerve and supplied by the supraorbital artery and anterior ethmoidal artery
Anterior ethmoidal artery
The anterior ethmoidal artery, also anterior ethmoid artery is an artery of the head.-Course:Once branching from the ophthalmic artery, it accompanies the nasociliary nerve through the anterior ethmoidal canal to supply the anterior and middle ethmoidal cells, frontal sinus, and anterosuperior...
.
Through its copious mucus production, the sinus is an essential part of the immune defense/air filtration carried out by the nose. Nasal and sinal mucosae are ciliated and move mucus to the choanae and finally to the stomach. The thick upper layers of nasal mucus trap bacteria and small particles in tissue abundantly provided with immune cells, antibodies, and antibacterial proteins. The layers beneath are thinner and provide a substrate in which the cilia are able to beat and move the upper layer with its debris through the ostia
Ostium
Ostium may refer to:Anatomy*Ostium of Fallopian tube*Ostium primum or foramen ovale of the developing heart*Ostium maxillare of the maxillary sinus*Ostium of female lepidoptera genitalia...
toward the choanae.
Inflammations of the frontal sinus can give rise to serious complications, as it is in close proximity to the orbit and cranial cavity (orbital cellulitis
Orbital cellulitis
Orbital cellulitisis an infection of eye tissues posterior to the orbital septum. It most commonly refers to an acute spread of infection into the eye socket from either the adjacent sinuses or through the blood...
, epidural and subdural abscess, meningitis
Meningitis
Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
).
External links
- http://www.scribd.com/full/24392438?access_key=key-xtjc9jvm7d4qp6zpdlt Radiological anatomy of frontal sinus