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Nasal cavity

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Title: Nasal cavity  
Author: World Heritage Encyclopedia
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Subject: Pterygopalatine fossa, Sphenopalatine foramen, Greater palatine foramen, Lesser palatine foramina, Palatovaginal canal
Collection: Nose
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Nasal cavity

Nasal cavity
Head and neck.
Conducting passages
Details
Latin cavum nasi; cavitas nasi
Identifiers
MeSH A04.531.449
Anatomical terminology

The nasal cavity (or nasal fossa) is a large air filled space above and behind the nose in the middle of the face. Each cavity is the continuation of one of the two nostrils.

Contents

  • Function 1
    • Walls 1.1
    • Cilia and mucus 1.2
    • Segments 1.3
  • Blood supply 2
  • Innervation 3
  • Diseases 4
  • Additional images 5
  • See also 6
  • External links 7

Function

The term "nasal cavity" can refer to each of the two sides of the nose or to the two sides combined, the former usage being more commonly applied to living persons and the latter usage being more commonly applied to dried skull anatomy. The two nasal cavities condition the air to be received by the other areas of the respiratory tract. Owing to the large surface area provided by the nasal conchae (also known as turbinates), the air passing through the nasal cavity is warmed or cooled to within 1 degree of body temperature. In addition, the air is humidified, and dust and other particulate matter is removed by vibrissae, short, thick hairs, present in the vestibule. The entire mucosa of the nasal fossae is covered by a blanket of mucus, which lies superficial to the microscopic cilia and also filters inspired air, The cilia of the respiratory epithelium move the secreted mucus and particulate matter posteriorly towards the pharynx where it passes into the esophagus and is digested in the stomach. The nasal cavity also houses our sense of smell and contributes greatly to taste sensation through its posterior communication with the mouth via the choanae.

Walls

The lateral wall of each nasal cavity is mainly made up by the maxilla, however there is a deficiency that is compensated by: the perpendicular plate of the palatine bone, the medial pterygoid plate, the labyrinth of ethmoid and the inferior concha. The paranasal sinuses are connected to the nasal cavity through small orifices called ostia. Most of these ostia communicate with the nose through the lateral nasal wall, via a semi-lunar depression in it known as the infundibulum. The infundibulum is bound laterally by a projection known as the uncinate process.

The roof of each nasal cavity is formed in its upper third to one half by the nasal bone and more inferiorly by the junctions of the upper lateral cartilage and nasal septum. Connective tissue and skin cover the bony and cartilaginous components of the dorsum of the nose.

The floor of the nasal cavities, which also form the roof of the mouth, is made up by the bones of the hard palate: the horizontal plate of the palatine bone posteriorly and the palatine process of the maxilla anteriorly. To the front of the nasal cavity is the nasal vestibule and external opening, while the back blends, via the choanae, into the nasopharynx.

The nasal cavity is divided in two by a vertical fin called the septum and has a role in pheromone detection.

Cilia and mucus

Cilia and mucus along the inside wall of the nasal cavity traps and removes dust and pathogens from the air as it flows through the nasal cavity. The cilia move the mucus down the nasal cavity to the pharynx, where it can be swallowed.

Segments

The nasal cavity is divided into two segments: the respiratory segment and the olfactory segment.

  • The respiratory segment comprises most of each nasal fossa and is lined with ciliated pseudostratified columnar epithelium (also called respiratory epithelium). The conchae, or turbinates, are located in this region. The turbinates have a very vascularized lamina propria (erectile tissue) allowing the venous plexuses of their mucosa to engorge with blood, restricting airflow and causing air to be directed to the other side of the nose, which acts in concert by shunting blood out of its turbinates. This cycle occurs approximately every two and a half hours.
  • The olfactory segment is lined with a specialized type of pseudostratified columnar epithelium, known as olfactory epithelium, which contains receptors for the sense of the smell. This segment is located in and beneath the mucosa of the roof of each nasal cavity and the medial side of each middle turbinate. Histological sections appear yellowish-brown due to the presence of lipofuscin pigments. Olfactory mucosal cell types include bipolar neurons, supporting (sustentacular) cells, basal cells, and Bowman's glands. The axons of the bipolar neurons form the olfactory nerve (cranial nerve I) which enters the brain through the cribiform plate. Bowman's glands are serous glands in the lamina propria, whose secretions trap and dissolve odoriferous substances.

Blood supply

There is a rich blood supply to the nasal cavity. In some animals, such as dogs, the capillary beds flowing through the nasal cavity help cool the blood flow to the brain.

Blood supply comes from branches of both the internal and external carotid artery, including branches of the facial artery and maxillary artery. The named arteries of the nose are:[1]

Innervation

Innervation of the nasal cavity responsible for the sense of smell is via the olfactory nerve, which sends microscopic fibers from the olfactory bulb through the cribriform plate to reach the top of the nasal cavity.

General sensory innervation is by branches of the trigeminal nerve (V1 & V2):

There are two passages in the nasal cavity, not to be confused with nostrils.The entire nasal cavity is innervated by autonomic fibers. Sympathetic innervation to the blood vessels of the mucosa causes them to constrict, while the control of secretion by the mucous glands is carried on postganglionic parasympathetic nerve fibers originating from the facial nerve.

Diseases

Diseases of the nasal cavity include viral, bacterial and fungal infections, nasal cavity tumors, both benign and much more often malignant, as well as inflammations of the nasal mucosa. Many problems can affect the nose, including:

Additional images

See also

External links

  • lesson9 at The Anatomy Lesson by Wesley Norman (Georgetown University)
  • Gross anatomy dissection of the nasal cavity, video [1] and [2]
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