Atlas of Anatomy. Head and Neuroanatomy. Michael Schuenke

7. Nose

7.1 Nose, Overview

A Overview of the nose and paranasal sinuses

a Coronal section, anterior view, b Transverse section, superior view. The reader is assumed to be familiar with the bony anatomy of the nasal cavity (especially the openings of the various passages below the nasal conchae, seep. 19ff). The nasal cavities and paranasal sinuses are arranged in pairs. The left and right nasal cavities are separated by the nasal septum and have an approximately triangular shape. Below the base of the triangle is the oral cavity. The following paired paranasal sinuses are shown in the drawings:

 Frontal sinus

 Ethmoid cells (ethmoid sinus*)

 Maxillary sinus

 Sphenoid sinus

The interior of each sinus is lined with ciliated respiratory epithelium (see p. 118).

 The term “ethmoid sinus” has been dropped from the latest anatomical nomenclature, although it is still widely used by medical practitioners.

В Mucosa of the nasal cavity

a Mucosa of the nasal septum, parasagittal section viewed from the left side, b Mucosa of the right lateral nasal wall, viewed from the left side, c Posterior view through the choanae into the nasal cavity.

While the medial wall of the nasal cavity is smooth, its lateral wall is raised into folds by the three conchae (superior, middle, and inferior concha). These increase the surface area of the nasal cavity, enabling it to warm and humidify the inspired air more efficiently (see also p. 118). A section of the right sphenoid sinus is shown in b. The choanae (c) are the posterior openings by which the nasal cavity communicates with the nasopharynx. Note the close proximity of the choanae to the pharyngotympanic (auditory) tube and pharyngeal tonsil (see p. 110).

7.2 Nasal Cavity: Neurovascular Supply

A Vessels and nerves of the nasal septum with the mucosa removed

Parasagittal section, viewed from the left side. The arterial supply of the nasal septum is of particular clinical interest in the diagnosis and treatment of nosebleed (see C).

В Vessels and nerves of the right lateral nasal wall

Left lateral view. The pterygopalatine ganglion, an important relay in the parasympathetic nervous system (seepp.81 and 101), has been exposed here by partial resection of the sphenoid bone. The nerve fibers arising from it pass to the small nasal glands of the nasal conchae, entering the conchae from the posterior side with the blood vessels. At the level of the superior concha, the olfactory fibers pass through the cribriform plate to the olfactory mucosa. The nasal wall is supplied from above by the two ethmoidal arteries, which arise from the ophthalmic artery. It is supplied from behind by the lateral posterior nasal arteries, which arise from the sphenopalatine artery.

The figures below depict the functional groups of arteries and nerves supplying the nasal cavity. As in a dissection, the septum is displayed first, followed by the lateral wall.

C Arteries of the nasal septum

Left lateral view. The vessels of the nasal septum arise from branches of the external and internal carotid arteries. The anterior part of the septum contains a highly vascularized area called Kiesselbach’s area (indicated by color shading), which is supplied by vessels from both major arteries. This area is the most common site of significant nosebleed.

D Nerves of the nasal septum

Left lateral view. The nasal septum receives its sensory innervation from branches of the trigeminal nerve (CN V). The anterosuperior part of the septum is supplied by branches of the ophthalmic division (CN V-|), and the rest by branches of the maxillary division (CN V2). Bundles of olfactory nerve fibers (CN I) arise from receptors in the olfactory mucosa.

E Arteries of the right lateral nasal wall

Left lateral view.

Note the vascular supply from the branches of the internal carotid artery (from above) and the external carotid artery (from behind).

F Nerves of the right lateral nasal wall

Left lateral view. The nasal wall derives its sensory innervation from branches of the ophthalmic division (CN VJ and the maxillary division (CN V2). Receptor neurons in the olfactory mucosa send their axons in the olfactory nerve (CN I) to the olfactory bulb (see p. 179 E).

7.3 Nose and Paranasal Sinuses, Histology and Clinical Anatomy

A Functional states of the mucosa in the nasal cavity

Coronal section, anterior view.

The function of the nasal mucosa is to warm and humidify the inspired air. This is accomplished by an increase of blood flow through the mucosa (see pp. 59 and 61), placing it in a congested (swollen) state. The mucous membranes are not simultaneously congested on both sides, however, but undergo a normal cycle of congestion and decongestion that lasts approximately 6 hours (the right side is decongested in the drawing). Examination of the nasal cavity can be facilitated by first administering a decongestant to shrink the mucosa, roughly as it appears here on the left side.

В Histology of the nasal mucosa

The surface of the pseudostratified respiratory epithelium of the nasal mucosa consists of kinocilia-bearing cells and goblet cells, which secrete their mucous into a watery film on the epithelial surface. Serous and seromucous glands are embedded in the connective tissue and also release secretions into the superficial fluid film. The directional fluid flow produced by the cilia (see C and D) is an important component of the nonspecific immune response. If coordinated beating of the cilia is impaired, the patient will suffer chronic recurring infections of the respiratory tract.

C Normal drainage of secretions from the paranasal sinus

Left lateral view. The beating cilia propel the mucous blanket over the cilia and through the choana into the nasopharynx, where it is swallowed.

D Direction of ciliary beating and fluid flow in the right maxillary sinus and frontal sinus

Schematic coronal sections of the right maxillary sinus (a) and frontal sinus (b), anterior view. The location of the sinuses is shown in C. Beating of the cilia produces a flow of fluid in the paranasal sinuses that is always directed toward the sinus ostium. This clears the sinus of particles and microorganisms that are trapped in the mucous layer. If the ostium is obstructed due to swelling of the mucosa, inflammation may develop in the affected sinus {sinusitis). This occurs most commonly in the ostiomeatal unit of the maxillary sinus—ethmoid ostium (see pp.20 and 21) (after Stamm berger and Hanke).

E Anterior and posterior rhinoscopy

a Anterior rhinoscopy is a procedure for inspection of the nasal cavity. Two different positions (I, II) are used to ensure that all of the anterior nasal cavity is examined.

b In posterior rhinoscopy, the choanae and pharyngeal tonsil are accessible to clinical examination. The rhinoscope can be angled and rotated to demonstrate the structures shown in the composite image. Today the rhinoscope is frequently replaced by an endoscope.

F Endoscopy of the maxillary sinus

Anterior view. The maxillary sinus is not accessible to direct inspection and must therefore be examined with an endoscope. To enter the maxillary sinus, the examiner pierces the thin bony wall below the inferior concha with a trocar and advances the endoscope through the opening. The scope can then be angled and rotated to inspect all of the mucosal surfaces.

C Sites of arterial ligation for the treatment of severe nosebleed

If a severe nosebleed cannot be controlled with ordinary intranasal packing, it may be necessary to ligate relatively large arterial vessels. The following arteries may be ligated:

* Maxillary artery or sphenopalatine artery (a)

* External carotid artery (a)

* Both ethmoidal arteries in the orbit (b)