Nasal cavity






The nasal cavity is a large, air-filled space above and behind the nose.



The nasal septum divides the cavity into two cavities, or fossae.



It is the uppermost part of the respiratory system and provides the nasal passage for inhaled air from the nostrils to the nasopharynx and rest of the respiratory tract.



The paranasal sinuses surround and drain into the nasal cavity.



The lateral wall of each nasal cavity mainly consists of the maxilla.



The paranasal sinuses are connected to the nasal cavity through  ostia. 



Most of these ostia communicate with the nose through the lateral nasal wall, via a semi-lunar depression in it known as the semilunar hiatus. 



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 nasal cavity.



The floor of the nasal cavities is also form the roof of the mouth.



The floor of the nasal cavities 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. 



The most anterior part of the nasal cavity is the nasal vestibule.



The vestibule is enclosed cartilages of the nose and lined by stratified squamous cells.



The vestibule changes into the typical respiratory epithelium that lines the rest of the nasal cavity and respiratory tract. 



Inside the nostrils of the vestibule are the nasal hair.



Nasal hairs filter dust and other matter that are breathed in. 



The back of the cavity blends from the choanae, into the nasopharynx.



The nasal cavity is divided in two by the nasal septum. 



On the side of each nasal cavity are  3 horizontal outgrowths called nasal conchae or turbinates. 



Turbinates disrupt airflow, directing air toward the olfactory epithelium on the surface of the turbinates and the septum. 



The vomeronasal organ at the back of the septum and has a role in pheromone detection.



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



The respiratory segment comprises most of each nasal cavity.



The respiratory segment of the nasal cavity is lined with ciliated pseudostratified columnar epithelium.



The respiratory segment of the nasal cavity  includes the conchae.



Turbinates are vascularized lamina propria that allow the venous plexuses of their mucosa to engorge with blood.



When engorged with blood it restricts 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 vascular cycle occurs approximately every two and a half hours.



The olfactory segment is lined with a pseudostratified columnar epithelium, known as olfactory epithelium, which contains receptors for the sense of the smell. 



The olfactory segment is located in and beneath the mucosa of the roof of each nasal cavity and on the medial side of each middle turbinate.



The olfactory segment’s mucosal cell types include:  bipolar neurons, supporting cells, basal cells, and Bowman’s glands. 



The axons of the bipolar neurons form the olfactory nerve, cranial nerve I,  enters the brain through the cribriform plate. 



Bowman’s glands in the lamina propria, 


are serous glands whose secretions trap and dissolve odoriferous substances.



The blood supply to the nasal cavity 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:



Sphenopalatine artery and greater palatine artery, branches of the maxillary artery.



Anterior ethmoidal artery and posterior ethmoidal artery, branches of the ophthalmic artery.



Septal branches of the superior labial artery, a branch of the facial artery, which supplies the vestibule of the nasal cavity.



The nasal cavity innervation is responsible for the sense of smell is via the olfactory nerve.



The olfactory nerve sends neural fibers from the olfactory bulb through the cribriform plate to reach the top of the nasal cavity.



The nasal cavity therefore houses the sense of smell and contributes to taste sensation through its posterior communication with the mouth via the choanae.



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



Nasociliary nerve (V1)



Nasopalatine nerve (V2)



Posterior nasal branches of Maxillary nerve (V2)



The nasal cavity is innervated by autonomic fibers: 



Sympathetic innervation to the blood vessels of the mucosa causes constriction.



Postganglionic parasympathetic nerve fibers originating from the facial nerve control of secretion by the mucous glands



The large surface area provided by the nasal conchae allows the air passing through the nasal cavity to be warmed or cooled to within 1 degree of body temperature. 



The large surface area humidifies the air, and dust and other particulate matter is removed by nasal hair in the nostrils. 



The mucosa of the nasal cavity is covered by mucus, which lies superficial to the microscopic cilia and also filters inspired air. 



The cilia in 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 compromises include viral, bacterial, fungal infections, tumors, both benign and much more often malignant, as well as inflammations of the nasal mucosa. 




Nasal cavity problems include: 



Deviated septum 



Nasal polyps 









Nasal fractures



Common cold



Sinonasal tumors

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