Anatomy of the Nasal Cavity
NASAL CAVITY
OBJECTIVES
§ Describe the main regions and features of the nasal cavity, including the various points of draining from the nasolacrimal duct and the nasal sinuses.
§ Describe the development and organization of the paranasal sinuses, and the significance of the maxillary sinus.
§ Describe the relationship of the tonsillar tissue of the oropharynx and nasopharynx.
§ Describe the sensory and parasympathetic innervation of the nasal cavity.
§ Describe the arterial supply to the nasocavity and nasopharynx.
Boundaries
§ The nasal cavity is somewhat triangular in appearance in frontal section.
§ base formed by part of the maxilla, a lateral wall, and a medial wall.
§ medial wall consists of two thin bones (i.e., vomer and perpendicular plate of the ethmoid) plus the septal cartilage.
§ anterior-posterior extent of the nasal cavity extends from the nares to the choana, posteriorly.
§ The anteromost portion of the nasal cavity is known as the vestibule. Benign nosebleeds are common from this region.
Conchae and Meatuses
§ The lateral features the conchae and meatuses (i.e., spaces) beneath them.
The conchae
§ also referred to as the turbinates
§ thin, curved, bones that are covered by mucosa.
§ The most prominent of the conchae are the inferior and middle, with the superior being relatively small and variable.
§ Occasionally, one can discern a supreme conchae in the area of the sphenoethmoidal recess.
§ The airway underneath each concha is a meatus.
The mucosa
§ covers the conchae
§ richly supplied with a vascular network, which can take on the properties of erectile tissue.
§ Active vasodialation
Knowledge of the relations of various meatuses is of clinical importance.
§ the nasolacrimal duct drains into the inferior meatus.
§ The maxillary and frontal sinuses reliably drain into the middle meatus, also some ethmoidal cells.
§ Other ethmoidal cells enter the nasal cavity in the region of the superior meatus.
Paranasal Sinuses
§ The paranasal sinuses are diverticula of the nasal cavity that develop out of the diploe.
§ Rudimentary in children, not fully developed until after puberty
§ Gives us our adult nasal feature
§ It is the development of these air sinuses around puberty that gives the adult facial features.
§ The sinuses are somewhat irregular but frontal, maxillary, and sphenoid sinuses are generally paired.
§ The ethmoidal sinus is a collection of air cells that are quite variable in number.
§ The maxillary sinus** is the clinically most important
this is the only one not to drain well by gravity
reason is that its ostium into the middle meatus lies high up on its medial wall.
At risk for housing infections
Nerve supply:
§ Air filled spaces continuous with nasal cavity
§ Develop from middle bone layer
§ Lined with mucousa, continuous with nasal cavity (ciliated-move mucous)
Nerve Supply
§ The nasal cavity contains CN I, which is formed by elements that are distributed only in the upper reaches of the nasal mucosa; e.g., over the superior concha and corresponding zones on the septum.
§ The nerves containing general sensory and parasympathetic fibers enter the nasal cavity through the sphenopalatine foramen just posterior to the middle concha.
§ These nerves are derived from the pterygopalatine ganglion that has an intimate relationship with the maxillary nerve.
§ The region over the septum and anterior portion over the hard palate is innervated by the nasopalatine nerve.
courses medially over the sphenoid bone to gain the septum
then courses anteriorly to penetrate the incisive foramen in the hard palate.
§ The posterior nerves of the nasal cavity are the lateral posterior superior and inferior.
§ These are largely responsible for the innervation of the lateral wall.
§ The anterior portion of the cavity is innervated by branches of the ophthalmic nerve (VI).
§ Greater palatine n.
§ Lesser palatine n.
§ Greater petrosal n.
Blood Supply
§ The arterial supply generally follows the distribution of the major nerves.
§ These vessels are derived from the sphenopalatine artery, which is a branch off the maxillary artery.
§ While nosebleeds are common (epistaxis), most serious bleeding typically is from the rupture of the sphenopalatine artery just after it enters the nasal cavity.
Clinical Correlates
§ the paranasal sinuses are of importance as they are frequently involved as sites of infections.
§ Of these, the maxillary sinus is the most important because of its rather indifferent capacity for draining by gravity.
§ Also, fractures of the nose may produce a difficult to control hemorrhage if the sphenopalatine artery is involved. (pulsating
§ Finally, with fracturing of the cribiform plate in the anterior cranial fossa, CSF may leak into and out of the nasal cavity.
Tags: choana, conchae, cribiform plate, ethmoidal cells, Greater palatine, maxillary sinus, meatus, middle meatus, mucousa, nasal cavity, nasolacrimal duct, nasopharynx, nose fractures, oropharynx, paranasal sinuses, parasympathetic innervation, sphenoethmoidal recess, sphenopalatine artery, superior concha, superior meatus, tonsillar tissue, turbinates, vasodialation
